Shutdown host sockets on internal shutdown

This is required to make the shutdown visible to peers outside the
sandbox.

The readClosed / writeClosed fields were dropped, as they were
preventing a shutdown socket from reading the remainder of queued bytes.
The host syscalls will return the appropriate errors for shutdown.

The control message tests have been split out of socket_unix.cc to make
the (few) remaining tests accessible to testing inherited host UDS,
which don't support sending control messages.

Updates #273

PiperOrigin-RevId: 251763060

10 files changed, 1650 insertions, 1621 deletions

diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 3ed137006..e4ec0f62c 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -15,6 +15,7 @@
 package host
 
 import (
+	"fmt"
 	"sync"
 	"syscall"
 
@@ -51,20 +52,6 @@ type ConnectedEndpoint struct {
 	// ref keeps track of references to a connectedEndpoint.
 	ref refs.AtomicRefCount
 
-	// mu protects fd, readClosed and writeClosed.
-	mu sync.RWMutex `state:"nosave"`
-
-	// file is an *fd.FD containing the FD backing this endpoint. It must be
-	// set to nil if it has been closed.
-	file *fd.FD `state:"nosave"`
-
-	// readClosed is true if the FD has read shutdown or if it has been closed.
-	readClosed bool
-
-	// writeClosed is true if the FD has write shutdown or if it has been
-	// closed.
-	writeClosed bool
-
 	// If srfd >= 0, it is the host FD that file was imported from.
 	srfd int `state:"wait"`
 
@@ -78,6 +65,13 @@ type ConnectedEndpoint struct {
 	// prevent lots of small messages from filling the real send buffer
 	// size on the host.
 	sndbuf int `state:"nosave"`
+
+	// mu protects the fields below.
+	mu sync.RWMutex `state:"nosave"`
+
+	// file is an *fd.FD containing the FD backing this endpoint. It must be
+	// set to nil if it has been closed.
+	file *fd.FD `state:"nosave"`
 }
 
 // init performs initialization required for creating new ConnectedEndpoints and
@@ -208,9 +202,6 @@ func newSocket(ctx context.Context, orgfd int, saveable bool) (*fs.File, error)
 func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.ControlMessages, from tcpip.FullAddress) (uintptr, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return 0, false, syserr.ErrClosedForSend
-	}
 
 	if !controlMessages.Empty() {
 		return 0, false, syserr.ErrInvalidEndpointState
@@ -244,8 +235,13 @@ func (c *ConnectedEndpoint) SendNotify() {}
 // CloseSend implements transport.ConnectedEndpoint.CloseSend.
 func (c *ConnectedEndpoint) CloseSend() {
 	c.mu.Lock()
-	c.writeClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_WR); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed write shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // CloseNotify implements transport.ConnectedEndpoint.CloseNotify.
@@ -255,9 +251,7 @@ func (c *ConnectedEndpoint) CloseNotify() {}
 func (c *ConnectedEndpoint) Writable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventOut)&waiter.EventOut != 0
 }
 
@@ -285,9 +279,6 @@ func (c *ConnectedEndpoint) EventUpdate() {
 func (c *ConnectedEndpoint) Recv(data [][]byte, creds bool, numRights uintptr, peek bool) (uintptr, uintptr, transport.ControlMessages, bool, tcpip.FullAddress, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return 0, 0, transport.ControlMessages{}, false, tcpip.FullAddress{}, false, syserr.ErrClosedForReceive
-	}
 
 	var cm unet.ControlMessage
 	if numRights > 0 {
@@ -344,31 +335,34 @@ func (c *ConnectedEndpoint) RecvNotify() {}
 // CloseRecv implements transport.Receiver.CloseRecv.
 func (c *ConnectedEndpoint) CloseRecv() {
 	c.mu.Lock()
-	c.readClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_RD); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed read shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // Readable implements transport.Receiver.Readable.
 func (c *ConnectedEndpoint) Readable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventIn)&waiter.EventIn != 0
 }
 
 // SendQueuedSize implements transport.Receiver.SendQueuedSize.
 func (c *ConnectedEndpoint) SendQueuedSize() int64 {
-	// SendQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): SendQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
 // RecvQueuedSize implements transport.Receiver.RecvQueuedSize.
 func (c *ConnectedEndpoint) RecvQueuedSize() int64 {
-	// RecvQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): RecvQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
diff --git a/pkg/sentry/fs/host/socket_test.go b/pkg/sentry/fs/host/socket_test.go
index 06392a65a..bc3ce5627 100644
--- a/pkg/sentry/fs/host/socket_test.go
+++ b/pkg/sentry/fs/host/socket_test.go
@@ -198,20 +198,6 @@ func TestListen(t *testing.T) {
 	}
 }
 
-func TestSend(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if _, _, err := e.Send(nil, transport.ControlMessages{}, tcpip.FullAddress{}); err != syserr.ErrClosedForSend {
-		t.Errorf("Got %#v.Send() = %v, want = %v", e, err, syserr.ErrClosedForSend)
-	}
-}
-
-func TestRecv(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if _, _, _, _, _, _, err := e.Recv(nil, false, 0, false); err != syserr.ErrClosedForReceive {
-		t.Errorf("Got %#v.Recv() = %v, want = %v", e, err, syserr.ErrClosedForReceive)
-	}
-}
-
 func TestPasscred(t *testing.T) {
 	e := ConnectedEndpoint{}
 	if got, want := e.Passcred(), false; got != want {
@@ -244,20 +230,6 @@ func TestQueuedSize(t *testing.T) {
 	}
 }
 
-func TestReadable(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if got, want := e.Readable(), true; got != want {
-		t.Errorf("Got %#v.Readable() = %t, want = %t", e, got, want)
-	}
-}
-
-func TestWritable(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if got, want := e.Writable(), true; got != want {
-		t.Errorf("Got %#v.Writable() = %t, want = %t", e, got, want)
-	}
-}
-
 func TestRelease(t *testing.T) {
 	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
@@ -272,131 +244,3 @@ func TestRelease(t *testing.T) {
 		t.Errorf("got = %#v, want = %#v", c, want)
 	}
 }
-
-func TestClose(t *testing.T) {
-	type testCase struct {
-		name  string
-		cep   *ConnectedEndpoint
-		addFD bool
-		f     func()
-		want  *ConnectedEndpoint
-	}
-
-	var tests []testCase
-
-	// nil is the value used by ConnectedEndpoint to indicate a closed file.
-	// Non-nil files are used to check if the file gets closed.
-
-	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c := &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseSend then CloseRecv",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseRecv then CloseSend",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	for _, test := range tests {
-		if test.addFD {
-			fdnotifier.AddFD(int32(test.cep.file.FD()), nil)
-		}
-		if test.f(); !reflect.DeepEqual(test.cep, test.want) {
-			t.Errorf("%s: got = %#v, want = %#v", test.name, test.cep, test.want)
-		}
-	}
-}
diff --git a/runsc/boot/filter/config.go b/runsc/boot/filter/config.go
index 652da1cef..ef2dbfad2 100644
--- a/runsc/boot/filter/config.go
+++ b/runsc/boot/filter/config.go
@@ -246,6 +246,10 @@ var allowedSyscalls = seccomp.SyscallRules{
 	},
 	syscall.SYS_SETITIMER: {},
 	syscall.SYS_SHUTDOWN: []seccomp.Rule{
+		// Used by fs/host to shutdown host sockets.
+		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_RD)},
+		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_WR)},
+		// Used by unet to shutdown connections.
 		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_RDWR)},
 	},
 	syscall.SYS_SIGALTSTACK:     {},
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 7633ab162..0cb7b47b6 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -2096,6 +2096,7 @@ cc_binary(
     deps = [
         ":socket_generic_test_cases",
         ":socket_test_util",
+        ":socket_unix_cmsg_test_cases",
         ":socket_unix_test_cases",
         ":unix_domain_socket_test_util",
         "//test/util:test_main",
@@ -2369,6 +2370,7 @@ cc_binary(
     deps = [
         ":socket_generic_test_cases",
         ":socket_test_util",
+        ":socket_unix_cmsg_test_cases",
         ":socket_unix_test_cases",
         ":unix_domain_socket_test_util",
         "//test/util:test_main",
@@ -2491,6 +2493,26 @@ cc_library(
 )
 
 cc_library(
+    name = "socket_unix_cmsg_test_cases",
+    testonly = 1,
+    srcs = [
+        "socket_unix_cmsg.cc",
+    ],
+    hdrs = [
+        "socket_unix_cmsg.h",
+    ],
+    deps = [
+        ":socket_test_util",
+        ":unix_domain_socket_test_util",
+        "//test/util:test_util",
+        "//test/util:thread_util",
+        "@com_google_absl//absl/strings",
+        "@com_google_googletest//:gtest",
+    ],
+    alwayslink = 1,
+)
+
+cc_library(
     name = "socket_stream_blocking_test_cases",
     testonly = 1,
     srcs = [
@@ -2733,6 +2755,7 @@ cc_binary(
     linkstatic = 1,
     deps = [
         ":socket_test_util",
+        ":socket_unix_cmsg_test_cases",
         ":socket_unix_test_cases",
         ":unix_domain_socket_test_util",
         "//test/util:test_main",
diff --git a/test/syscalls/linux/socket_abstract.cc b/test/syscalls/linux/socket_abstract.cc
index 503ba986b..715d87b76 100644
--- a/test/syscalls/linux/socket_abstract.cc
+++ b/test/syscalls/linux/socket_abstract.cc
@@ -17,6 +17,7 @@
 #include "test/syscalls/linux/socket_generic.h"
 #include "test/syscalls/linux/socket_test_util.h"
 #include "test/syscalls/linux/socket_unix.h"
+#include "test/syscalls/linux/socket_unix_cmsg.h"
 #include "test/syscalls/linux/unix_domain_socket_test_util.h"
 #include "test/util/test_util.h"
 
@@ -38,5 +39,9 @@ INSTANTIATE_TEST_SUITE_P(
     AbstractUnixSockets, UnixSocketPairTest,
     ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
 
+INSTANTIATE_TEST_SUITE_P(
+    AbstractUnixSockets, UnixSocketPairCmsgTest,
+    ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
+
 }  // namespace testing
 }  // namespace gvisor
diff --git a/test/syscalls/linux/socket_filesystem.cc b/test/syscalls/linux/socket_filesystem.cc
index e38a320f6..74e262959 100644
--- a/test/syscalls/linux/socket_filesystem.cc
+++ b/test/syscalls/linux/socket_filesystem.cc
@@ -17,6 +17,7 @@
 #include "test/syscalls/linux/socket_generic.h"
 #include "test/syscalls/linux/socket_test_util.h"
 #include "test/syscalls/linux/socket_unix.h"
+#include "test/syscalls/linux/socket_unix_cmsg.h"
 #include "test/syscalls/linux/unix_domain_socket_test_util.h"
 #include "test/util/test_util.h"
 
@@ -38,5 +39,9 @@ INSTANTIATE_TEST_SUITE_P(
     FilesystemUnixSockets, UnixSocketPairTest,
     ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
 
+INSTANTIATE_TEST_SUITE_P(
+    FilesystemUnixSockets, UnixSocketPairCmsgTest,
+    ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
+
 }  // namespace testing
 }  // namespace gvisor
diff --git a/test/syscalls/linux/socket_unix.cc b/test/syscalls/linux/socket_unix.cc
index 95cf8d2a3..875f0391f 100644
--- a/test/syscalls/linux/socket_unix.cc
+++ b/test/syscalls/linux/socket_unix.cc
@@ -32,6 +32,9 @@
 #include "test/util/test_util.h"
 #include "test/util/thread_util.h"
 
+// This file contains tests specific to Unix domain sockets. It does not contain
+// tests for UDS control messages. Those belong in socket_unix_cmsg.cc.
+//
 // This file is a generic socket test file. It must be built with another file
 // that provides the test types.
 
@@ -40,1430 +43,6 @@ namespace testing {
 
 namespace {
 
-TEST_P(UnixSocketPairTest, BasicFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvSingleFD(sockets->second_fd(), &fd, received_data,
-                                       sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, BasicTwoFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair1 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  auto pair2 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  int sent_fds[] = {pair1->second_fd(), pair2->second_fd()};
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendFDs(sockets->first_fd(), sent_fds, 2, sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  int received_fds[] = {-1, -1};
-
-  ASSERT_NO_FATAL_FAILURE(RecvFDs(sockets->second_fd(), received_fds, 2,
-                                  received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[0], pair1->first_fd()));
-  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[1], pair2->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, BasicThreeFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair1 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  auto pair2 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  auto pair3 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  int sent_fds[] = {pair1->second_fd(), pair2->second_fd(), pair3->second_fd()};
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendFDs(sockets->first_fd(), sent_fds, 3, sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  int received_fds[] = {-1, -1, -1};
-
-  ASSERT_NO_FATAL_FAILURE(RecvFDs(sockets->second_fd(), received_fds, 3,
-                                  received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[0], pair1->first_fd()));
-  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[1], pair2->first_fd()));
-  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[2], pair3->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, BadFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  int sent_fd = -1;
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(sizeof(sent_fd))];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  cmsg->cmsg_len = CMSG_LEN(sizeof(sent_fd));
-  cmsg->cmsg_level = SOL_SOCKET;
-  cmsg->cmsg_type = SCM_RIGHTS;
-  memcpy(CMSG_DATA(cmsg), &sent_fd, sizeof(sent_fd));
-
-  struct iovec iov;
-  iov.iov_base = sent_data;
-  iov.iov_len = sizeof(sent_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(sendmsg)(sockets->first_fd(), &msg, 0),
-              SyscallFailsWithErrno(EBADF));
-}
-
-// BasicFDPassNoSpace starts off by sending a single FD just like BasicFDPass.
-// The difference is that when calling recvmsg, no space for FDs is provided,
-// only space for the cmsg header.
-TEST_P(UnixSocketPairTest, BasicFDPassNoSpace) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-
-  struct msghdr msg = {};
-  std::vector<char> control(CMSG_SPACE(0));
-  msg.msg_control = &control[0];
-  msg.msg_controllen = control.size();
-
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_controllen, 0);
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-// BasicFDPassNoSpaceMsgCtrunc sends an FD, but does not provide any space to
-// receive it. It then verifies that the MSG_CTRUNC flag is set in the msghdr.
-TEST_P(UnixSocketPairTest, BasicFDPassNoSpaceMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  std::vector<char> control(CMSG_SPACE(0));
-  msg.msg_control = &control[0];
-  msg.msg_controllen = control.size();
-
-  char received_data[sizeof(sent_data)];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_controllen, 0);
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-}
-
-// BasicFDPassNullControlMsgCtrunc sends an FD and sets contradictory values for
-// msg_controllen and msg_control. msg_controllen is set to the correct size to
-// accomidate the FD, but msg_control is set to NULL. In this case, msg_control
-// should override msg_controllen.
-TEST_P(UnixSocketPairTest, BasicFDPassNullControlMsgCtrunc) {
-  // FIXME(gvisor.dev/issue/207): Fix handling of NULL msg_control.
-  SKIP_IF(IsRunningOnGvisor());
-
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  msg.msg_controllen = CMSG_SPACE(1);
-
-  char received_data[sizeof(sent_data)];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_controllen, 0);
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-}
-
-// BasicFDPassNotEnoughSpaceMsgCtrunc sends an FD, but does not provide enough
-// space to receive it. It then verifies that the MSG_CTRUNC flag is set in the
-// msghdr.
-TEST_P(UnixSocketPairTest, BasicFDPassNotEnoughSpaceMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  std::vector<char> control(CMSG_SPACE(0) + 1);
-  msg.msg_control = &control[0];
-  msg.msg_controllen = control.size();
-
-  char received_data[sizeof(sent_data)];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_controllen, 0);
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-}
-
-// BasicThreeFDPassTruncationMsgCtrunc sends three FDs, but only provides enough
-// space to receive two of them. It then verifies that the MSG_CTRUNC flag is
-// set in the msghdr.
-TEST_P(UnixSocketPairTest, BasicThreeFDPassTruncationMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair1 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  auto pair2 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  auto pair3 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  int sent_fds[] = {pair1->second_fd(), pair2->second_fd(), pair3->second_fd()};
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendFDs(sockets->first_fd(), sent_fds, 3, sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  std::vector<char> control(CMSG_SPACE(2 * sizeof(int)));
-  msg.msg_control = &control[0];
-  msg.msg_controllen = control.size();
-
-  char received_data[sizeof(sent_data)];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(2 * sizeof(int)));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
-}
-
-// BasicFDPassUnalignedRecv starts off by sending a single FD just like
-// BasicFDPass. The difference is that when calling recvmsg, the length of the
-// receive data is only aligned on a 4 byte boundry instead of the normal 8.
-TEST_P(UnixSocketPairTest, BasicFDPassUnalignedRecv) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvSingleFDUnaligned(
-      sockets->second_fd(), &fd, received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
-}
-
-// BasicFDPassUnalignedRecvNoMsgTrunc sends one FD and only provides enough
-// space to receive just it. (Normally the minimum amount of space one would
-// provide would be enough space for two FDs.) It then verifies that the
-// MSG_CTRUNC flag is not set in the msghdr.
-TEST_P(UnixSocketPairTest, BasicFDPassUnalignedRecvNoMsgTrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(sizeof(int)) - sizeof(int)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_flags, 0);
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
-}
-
-// BasicTwoFDPassUnalignedRecvTruncationMsgTrunc sends two FDs, but only
-// provides enough space to receive one of them. It then verifies that the
-// MSG_CTRUNC flag is set in the msghdr.
-TEST_P(UnixSocketPairTest, BasicTwoFDPassUnalignedRecvTruncationMsgTrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  int sent_fds[] = {pair->first_fd(), pair->second_fd()};
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendFDs(sockets->first_fd(), sent_fds, 2, sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  // CMSG_SPACE rounds up to two FDs, we only want one.
-  char control[CMSG_SPACE(sizeof(int)) - sizeof(int)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
-}
-
-TEST_P(UnixSocketPairTest, ConcurrentBasicFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  int sockfd1 = sockets->first_fd();
-  auto recv_func = [sockfd1, sent_data]() {
-    char received_data[20];
-    int fd = -1;
-    RecvSingleFD(sockfd1, &fd, received_data, sizeof(received_data));
-    ASSERT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-    char buf[20];
-    ASSERT_THAT(ReadFd(fd, buf, sizeof(buf)),
-                SyscallSucceedsWithValue(sizeof(buf)));
-    ASSERT_THAT(WriteFd(fd, buf, sizeof(buf)),
-                SyscallSucceedsWithValue(sizeof(buf)));
-  };
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->second_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  ScopedThread t(recv_func);
-
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-  ASSERT_THAT(WriteFd(pair->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  char received_data[20];
-  ASSERT_THAT(ReadFd(pair->first_fd(), received_data, sizeof(received_data)),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  t.Join();
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-// FDPassNoRecv checks that the control message can be safely ignored by using
-// read(2) instead of recvmsg(2).
-TEST_P(UnixSocketPairTest, FDPassNoRecv) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  // Read while ignoring the passed FD.
-  char received_data[20];
-  ASSERT_THAT(
-      ReadFd(sockets->second_fd(), received_data, sizeof(received_data)),
-      SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  // Check that the socket still works for reads and writes.
-  ASSERT_NO_FATAL_FAILURE(
-      TransferTest(sockets->first_fd(), sockets->second_fd()));
-}
-
-// FDPassInterspersed1 checks that sent control messages cannot be read before
-// their associated data has been read.
-TEST_P(UnixSocketPairTest, FDPassInterspersed1) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char written_data[20];
-  RandomizeBuffer(written_data, sizeof(written_data));
-
-  ASSERT_THAT(WriteFd(sockets->first_fd(), written_data, sizeof(written_data)),
-              SyscallSucceedsWithValue(sizeof(written_data)));
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  // Check that we don't get a control message, but do get the data.
-  char received_data[20];
-  RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data));
-  EXPECT_EQ(0, memcmp(written_data, received_data, sizeof(written_data)));
-}
-
-// FDPassInterspersed2 checks that sent control messages cannot be read after
-// their assocated data has been read while ignoring the control message by
-// using read(2) instead of recvmsg(2).
-TEST_P(UnixSocketPairTest, FDPassInterspersed2) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char written_data[20];
-  RandomizeBuffer(written_data, sizeof(written_data));
-  ASSERT_THAT(WriteFd(sockets->first_fd(), written_data, sizeof(written_data)),
-              SyscallSucceedsWithValue(sizeof(written_data)));
-
-  char received_data[20];
-  ASSERT_THAT(
-      ReadFd(sockets->second_fd(), received_data, sizeof(received_data)),
-      SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-  EXPECT_EQ(0, memcmp(written_data, received_data, sizeof(written_data)));
-}
-
-TEST_P(UnixSocketPairTest, FDPassNotCoalesced) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data1[20];
-  RandomizeBuffer(sent_data1, sizeof(sent_data1));
-
-  auto pair1 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair1->second_fd(),
-                                       sent_data1, sizeof(sent_data1)));
-
-  char sent_data2[20];
-  RandomizeBuffer(sent_data2, sizeof(sent_data2));
-
-  auto pair2 =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair2->second_fd(),
-                                       sent_data2, sizeof(sent_data2)));
-
-  char received_data1[sizeof(sent_data1) + sizeof(sent_data2)];
-  int received_fd1 = -1;
-
-  RecvSingleFD(sockets->second_fd(), &received_fd1, received_data1,
-               sizeof(received_data1), sizeof(sent_data1));
-
-  EXPECT_EQ(0, memcmp(sent_data1, received_data1, sizeof(sent_data1)));
-  TransferTest(pair1->first_fd(), pair1->second_fd());
-
-  char received_data2[sizeof(sent_data1) + sizeof(sent_data2)];
-  int received_fd2 = -1;
-
-  RecvSingleFD(sockets->second_fd(), &received_fd2, received_data2,
-               sizeof(received_data2), sizeof(sent_data2));
-
-  EXPECT_EQ(0, memcmp(sent_data2, received_data2, sizeof(sent_data2)));
-  TransferTest(pair2->first_fd(), pair2->second_fd());
-}
-
-TEST_P(UnixSocketPairTest, FDPassPeek) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char peek_data[20];
-  int peek_fd = -1;
-  PeekSingleFD(sockets->second_fd(), &peek_fd, peek_data, sizeof(peek_data));
-  EXPECT_EQ(0, memcmp(sent_data, peek_data, sizeof(sent_data)));
-  TransferTest(peek_fd, pair->first_fd());
-  EXPECT_THAT(close(peek_fd), SyscallSucceeds());
-
-  char received_data[20];
-  int received_fd = -1;
-  RecvSingleFD(sockets->second_fd(), &received_fd, received_data,
-               sizeof(received_data));
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-  TransferTest(received_fd, pair->first_fd());
-  EXPECT_THAT(close(received_fd), SyscallSucceeds());
-}
-
-TEST_P(UnixSocketPairTest, BasicCredPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-  EXPECT_EQ(sent_creds.pid, received_creds.pid);
-  EXPECT_EQ(sent_creds.uid, received_creds.uid);
-  EXPECT_EQ(sent_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, SendNullCredsBeforeSoPassCredRecvEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds {
-    0, 65534, 65534
-  };
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, SendNullCredsAfterSoPassCredRecvEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  SetSoPassCred(sockets->second_fd());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds;
-  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, SendNullCredsBeforeSoPassCredSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->first_fd());
-
-  char received_data[20];
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-TEST_P(UnixSocketPairTest, SendNullCredsAfterSoPassCredSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  SetSoPassCred(sockets->first_fd());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-TEST_P(UnixSocketPairTest, SendNullCredsBeforeSoPassCredRecvEndAfterSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  SetSoPassCred(sockets->first_fd());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds;
-  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, WriteBeforeSoPassCredRecvEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds {
-    0, 65534, 65534
-  };
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, WriteAfterSoPassCredRecvEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  SetSoPassCred(sockets->second_fd());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  char received_data[20];
-
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds;
-  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, WriteBeforeSoPassCredSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  SetSoPassCred(sockets->first_fd());
-
-  char received_data[20];
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-TEST_P(UnixSocketPairTest, WriteAfterSoPassCredSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  SetSoPassCred(sockets->first_fd());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  char received_data[20];
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-TEST_P(UnixSocketPairTest, WriteBeforeSoPassCredRecvEndAfterSendEnd) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  SetSoPassCred(sockets->first_fd());
-
-  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
-              SyscallSucceedsWithValue(sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-
-  struct ucred received_creds;
-  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
-                                    received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds;
-  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-}
-
-TEST_P(UnixSocketPairTest, CredPassTruncated) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(0) + sizeof(pid_t)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  EXPECT_EQ(msg.msg_controllen, sizeof(control));
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
-
-  pid_t pid = 0;
-  memcpy(&pid, CMSG_DATA(cmsg), sizeof(pid));
-  EXPECT_EQ(pid, sent_creds.pid);
-}
-
-// CredPassNoMsgCtrunc passes a full set of credentials. It then verifies that
-// receiving the full set does not result in MSG_CTRUNC being set in the msghdr.
-TEST_P(UnixSocketPairTest, CredPassNoMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(sizeof(struct ucred))];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  // The control message should not be truncated.
-  EXPECT_EQ(msg.msg_flags, 0);
-  EXPECT_EQ(msg.msg_controllen, sizeof(control));
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(struct ucred)));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
-}
-
-// CredPassNoSpaceMsgCtrunc passes a full set of credentials. It then receives
-// the data without providing space for any credentials and verifies that
-// MSG_CTRUNC is set in the msghdr.
-TEST_P(UnixSocketPairTest, CredPassNoSpaceMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(0)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  // The control message should be truncated.
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-  EXPECT_EQ(msg.msg_controllen, sizeof(control));
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
-}
-
-// CredPassTruncatedMsgCtrunc passes a full set of credentials. It then receives
-// the data while providing enough space for only the first field of the
-// credentials and verifies that MSG_CTRUNC is set in the msghdr.
-TEST_P(UnixSocketPairTest, CredPassTruncatedMsgCtrunc) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(0) + sizeof(pid_t)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[sizeof(sent_data)] = {};
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  // The control message should be truncated.
-  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
-  EXPECT_EQ(msg.msg_controllen, sizeof(control));
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
-}
-
-TEST_P(UnixSocketPairTest, SoPassCred) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  int opt;
-  socklen_t optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_FALSE(opt);
-
-  optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_FALSE(opt);
-
-  SetSoPassCred(sockets->first_fd());
-
-  optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_TRUE(opt);
-
-  optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_FALSE(opt);
-
-  int zero = 0;
-  EXPECT_THAT(setsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &zero,
-                         sizeof(zero)),
-              SyscallSucceeds());
-
-  optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_FALSE(opt);
-
-  optLen = sizeof(opt);
-  EXPECT_THAT(
-      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
-      SyscallSucceeds());
-  EXPECT_FALSE(opt);
-}
-
-TEST_P(UnixSocketPairTest, NoDataCredPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct msghdr msg = {};
-
-  struct iovec iov;
-  iov.iov_base = sent_data;
-  iov.iov_len = sizeof(sent_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  char control[CMSG_SPACE(0)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  cmsg->cmsg_level = SOL_SOCKET;
-  cmsg->cmsg_type = SCM_CREDENTIALS;
-  cmsg->cmsg_len = CMSG_LEN(0);
-
-  ASSERT_THAT(RetryEINTR(sendmsg)(sockets->first_fd(), &msg, 0),
-              SyscallFailsWithErrno(EINVAL));
-}
-
-TEST_P(UnixSocketPairTest, NoPassCred) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  ASSERT_NO_FATAL_FAILURE(
-      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-
-  ASSERT_NO_FATAL_FAILURE(
-      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-}
-
-TEST_P(UnixSocketPairTest, CredAndFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  struct ucred sent_creds;
-
-  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendCredsAndFD(sockets->first_fd(), sent_creds,
-                                         pair->second_fd(), sent_data,
-                                         sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-  struct ucred received_creds;
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
-                                         &fd, received_data,
-                                         sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  EXPECT_EQ(sent_creds.pid, received_creds.pid);
-  EXPECT_EQ(sent_creds.uid, received_creds.uid);
-  EXPECT_EQ(sent_creds.gid, received_creds.gid);
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, FDPassBeforeSoPassCred) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  SetSoPassCred(sockets->second_fd());
-
-  char received_data[20];
-  struct ucred received_creds;
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
-                                         &fd, received_data,
-                                         sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds {
-    0, 65534, 65534
-  };
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, FDPassAfterSoPassCred) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  SetSoPassCred(sockets->second_fd());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  struct ucred received_creds;
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
-                                         &fd, received_data,
-                                         sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  struct ucred want_creds;
-  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
-  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
-
-  EXPECT_EQ(want_creds.pid, received_creds.pid);
-  EXPECT_EQ(want_creds.uid, received_creds.uid);
-  EXPECT_EQ(want_creds.gid, received_creds.gid);
-
-  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
-}
-
-TEST_P(UnixSocketPairTest, CloexecDroppedWhenFDPassed) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair = ASSERT_NO_ERRNO_AND_VALUE(
-      UnixDomainSocketPair(SOCK_SEQPACKET | SOCK_CLOEXEC).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  char received_data[20];
-  int fd = -1;
-  ASSERT_NO_FATAL_FAILURE(RecvSingleFD(sockets->second_fd(), &fd, received_data,
-                                       sizeof(received_data)));
-
-  EXPECT_THAT(fcntl(fd, F_GETFD), SyscallSucceedsWithValue(0));
-}
-
-TEST_P(UnixSocketPairTest, CloexecRecvFDPass) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(sizeof(int))];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  struct iovec iov;
-  char received_data[20];
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, MSG_CMSG_CLOEXEC),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
-  ASSERT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
-
-  int fd = -1;
-  memcpy(&fd, CMSG_DATA(cmsg), sizeof(int));
-
-  EXPECT_THAT(fcntl(fd, F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
-}
-
-TEST_P(UnixSocketPairTest, FDPassAfterSoPassCredWithoutCredSpace) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  SetSoPassCred(sockets->second_fd());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  char control[CMSG_LEN(0)];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[20];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-
-  EXPECT_EQ(msg.msg_controllen, sizeof(control));
-
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
-  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
-}
-
-// This test will validate that MSG_CTRUNC as an input flag to recvmsg will
-// not appear as an output flag on the control message when truncation doesn't
-// happen.
-TEST_P(UnixSocketPairTest, MsgCtruncInputIsNoop) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  char control[CMSG_SPACE(sizeof(int)) /* we're passing a single fd */];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  struct iovec iov;
-  char received_data[20];
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, MSG_CTRUNC),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-  ASSERT_NE(cmsg, nullptr);
-  ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
-  ASSERT_EQ(cmsg->cmsg_level, SOL_SOCKET);
-  ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
-
-  // Now we should verify that MSG_CTRUNC wasn't set as an output flag.
-  EXPECT_EQ(msg.msg_flags & MSG_CTRUNC, 0);
-}
-
-TEST_P(UnixSocketPairTest, FDPassAfterSoPassCredWithoutCredHeaderSpace) {
-  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-
-  char sent_data[20];
-  RandomizeBuffer(sent_data, sizeof(sent_data));
-
-  auto pair =
-      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
-
-  SetSoPassCred(sockets->second_fd());
-
-  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
-                                       sent_data, sizeof(sent_data)));
-
-  struct msghdr msg = {};
-  char control[CMSG_LEN(0) / 2];
-  msg.msg_control = control;
-  msg.msg_controllen = sizeof(control);
-
-  char received_data[20];
-  struct iovec iov;
-  iov.iov_base = received_data;
-  iov.iov_len = sizeof(received_data);
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-
-  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
-              SyscallSucceedsWithValue(sizeof(received_data)));
-
-  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
-  EXPECT_EQ(msg.msg_controllen, 0);
-}
-
 TEST_P(UnixSocketPairTest, InvalidGetSockOpt) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
   int opt;
@@ -1519,6 +98,14 @@ TEST_P(UnixSocketPairTest, RecvmmsgTimeoutAfterRecv) {
 TEST_P(UnixSocketPairTest, TIOCINQSucceeds) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
 
+  if (IsRunningOnGvisor()) {
+    // TODO(gvisor.dev/issue/273): Inherited host UDS don't support TIOCINQ.
+    // Skip the test.
+    int size = -1;
+    int ret = ioctl(sockets->first_fd(), TIOCINQ, &size);
+    SKIP_IF(ret == -1 && errno == ENOTTY);
+  }
+
   int size = -1;
   EXPECT_THAT(ioctl(sockets->first_fd(), TIOCINQ, &size), SyscallSucceeds());
   EXPECT_EQ(size, 0);
@@ -1544,6 +131,14 @@ TEST_P(UnixSocketPairTest, TIOCINQSucceeds) {
 TEST_P(UnixSocketPairTest, TIOCOUTQSucceeds) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
 
+  if (IsRunningOnGvisor()) {
+    // TODO(gvisor.dev/issue/273): Inherited host UDS don't support TIOCOUTQ.
+    // Skip the test.
+    int size = -1;
+    int ret = ioctl(sockets->second_fd(), TIOCOUTQ, &size);
+    SKIP_IF(ret == -1 && errno == ENOTTY);
+  }
+
   int size = -1;
   EXPECT_THAT(ioctl(sockets->second_fd(), TIOCOUTQ, &size), SyscallSucceeds());
   EXPECT_EQ(size, 0);
@@ -1580,19 +175,70 @@ TEST_P(UnixSocketPairTest, NetdeviceIoctlsSucceed) {
   }
 }
 
-TEST_P(UnixSocketPairTest, SocketShutdown) {
+TEST_P(UnixSocketPairTest, Shutdown) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
-  char buf[20];
+
   const std::string data = "abc";
-  ASSERT_THAT(WriteFd(sockets->first_fd(), data.c_str(), 3),
-              SyscallSucceedsWithValue(3));
+  ASSERT_THAT(WriteFd(sockets->first_fd(), data.c_str(), data.size()),
+              SyscallSucceedsWithValue(data.size()));
+
   ASSERT_THAT(shutdown(sockets->first_fd(), SHUT_RDWR), SyscallSucceeds());
   ASSERT_THAT(shutdown(sockets->second_fd(), SHUT_RDWR), SyscallSucceeds());
 
   // Shutting down a socket does not clear the buffer.
-  ASSERT_THAT(ReadFd(sockets->second_fd(), buf, 3),
-              SyscallSucceedsWithValue(3));
-  EXPECT_EQ(data, absl::string_view(buf, 3));
+  char buf[3];
+  ASSERT_THAT(ReadFd(sockets->second_fd(), buf, data.size()),
+              SyscallSucceedsWithValue(data.size()));
+  EXPECT_EQ(data, absl::string_view(buf, data.size()));
+}
+
+TEST_P(UnixSocketPairTest, ShutdownRead) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  ASSERT_THAT(shutdown(sockets->first_fd(), SHUT_RD), SyscallSucceeds());
+
+  // When the socket is shutdown for read, read behavior varies between
+  // different socket types. This is covered by the various ReadOneSideClosed
+  // test cases.
+
+  // ... and the peer cannot write.
+  const std::string data = "abc";
+  EXPECT_THAT(WriteFd(sockets->second_fd(), data.c_str(), data.size()),
+              SyscallFailsWithErrno(EPIPE));
+
+  // ... but the socket can still write.
+  ASSERT_THAT(WriteFd(sockets->first_fd(), data.c_str(), data.size()),
+              SyscallSucceedsWithValue(data.size()));
+
+  // ... and the peer can still read.
+  char buf[3];
+  EXPECT_THAT(ReadFd(sockets->second_fd(), buf, data.size()),
+              SyscallSucceedsWithValue(data.size()));
+  EXPECT_EQ(data, absl::string_view(buf, data.size()));
+}
+
+TEST_P(UnixSocketPairTest, ShutdownWrite) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  ASSERT_THAT(shutdown(sockets->first_fd(), SHUT_WR), SyscallSucceeds());
+
+  // When the socket is shutdown for write, it cannot write.
+  const std::string data = "abc";
+  EXPECT_THAT(WriteFd(sockets->first_fd(), data.c_str(), data.size()),
+              SyscallFailsWithErrno(EPIPE));
+
+  // ... and the peer read behavior varies between different socket types. This
+  // is covered by the various ReadOneSideClosed test cases.
+
+  // ... but the peer can still write.
+  char buf[3];
+  ASSERT_THAT(WriteFd(sockets->second_fd(), data.c_str(), data.size()),
+              SyscallSucceedsWithValue(data.size()));
+
+  // ... and the socket can still read.
+  EXPECT_THAT(ReadFd(sockets->first_fd(), buf, data.size()),
+              SyscallSucceedsWithValue(data.size()));
+  EXPECT_EQ(data, absl::string_view(buf, data.size()));
 }
 
 TEST_P(UnixSocketPairTest, SocketReopenFromProcfs) {
diff --git a/test/syscalls/linux/socket_unix_cmsg.cc b/test/syscalls/linux/socket_unix_cmsg.cc
new file mode 100644
index 000000000..b0ab26847
--- /dev/null
+++ b/test/syscalls/linux/socket_unix_cmsg.cc
@@ -0,0 +1,1473 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "test/syscalls/linux/socket_unix_cmsg.h"
+
+#include <errno.h>
+#include <net/if.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gtest/gtest.h"
+#include "absl/strings/string_view.h"
+#include "test/syscalls/linux/socket_test_util.h"
+#include "test/syscalls/linux/unix_domain_socket_test_util.h"
+#include "test/util/test_util.h"
+#include "test/util/thread_util.h"
+
+// This file contains tests for control message in Unix domain sockets.
+//
+// This file is a generic socket test file. It must be built with another file
+// that provides the test types.
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+TEST_P(UnixSocketPairCmsgTest, BasicFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvSingleFD(sockets->second_fd(), &fd, received_data,
+                                       sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, BasicTwoFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair1 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  auto pair2 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  int sent_fds[] = {pair1->second_fd(), pair2->second_fd()};
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendFDs(sockets->first_fd(), sent_fds, 2, sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  int received_fds[] = {-1, -1};
+
+  ASSERT_NO_FATAL_FAILURE(RecvFDs(sockets->second_fd(), received_fds, 2,
+                                  received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[0], pair1->first_fd()));
+  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[1], pair2->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, BasicThreeFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair1 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  auto pair2 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  auto pair3 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  int sent_fds[] = {pair1->second_fd(), pair2->second_fd(), pair3->second_fd()};
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendFDs(sockets->first_fd(), sent_fds, 3, sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  int received_fds[] = {-1, -1, -1};
+
+  ASSERT_NO_FATAL_FAILURE(RecvFDs(sockets->second_fd(), received_fds, 3,
+                                  received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[0], pair1->first_fd()));
+  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[1], pair2->first_fd()));
+  ASSERT_NO_FATAL_FAILURE(TransferTest(received_fds[2], pair3->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, BadFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  int sent_fd = -1;
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(sizeof(sent_fd))];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  cmsg->cmsg_len = CMSG_LEN(sizeof(sent_fd));
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  memcpy(CMSG_DATA(cmsg), &sent_fd, sizeof(sent_fd));
+
+  struct iovec iov;
+  iov.iov_base = sent_data;
+  iov.iov_len = sizeof(sent_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(sendmsg)(sockets->first_fd(), &msg, 0),
+              SyscallFailsWithErrno(EBADF));
+}
+
+// BasicFDPassNoSpace starts off by sending a single FD just like BasicFDPass.
+// The difference is that when calling recvmsg, no space for FDs is provided,
+// only space for the cmsg header.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassNoSpace) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+
+  struct msghdr msg = {};
+  std::vector<char> control(CMSG_SPACE(0));
+  msg.msg_control = &control[0];
+  msg.msg_controllen = control.size();
+
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_controllen, 0);
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+// BasicFDPassNoSpaceMsgCtrunc sends an FD, but does not provide any space to
+// receive it. It then verifies that the MSG_CTRUNC flag is set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassNoSpaceMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  std::vector<char> control(CMSG_SPACE(0));
+  msg.msg_control = &control[0];
+  msg.msg_controllen = control.size();
+
+  char received_data[sizeof(sent_data)];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_controllen, 0);
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+}
+
+// BasicFDPassNullControlMsgCtrunc sends an FD and sets contradictory values for
+// msg_controllen and msg_control. msg_controllen is set to the correct size to
+// accomidate the FD, but msg_control is set to NULL. In this case, msg_control
+// should override msg_controllen.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassNullControlMsgCtrunc) {
+  // FIXME(gvisor.dev/issue/207): Fix handling of NULL msg_control.
+  SKIP_IF(IsRunningOnGvisor());
+
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  msg.msg_controllen = CMSG_SPACE(1);
+
+  char received_data[sizeof(sent_data)];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_controllen, 0);
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+}
+
+// BasicFDPassNotEnoughSpaceMsgCtrunc sends an FD, but does not provide enough
+// space to receive it. It then verifies that the MSG_CTRUNC flag is set in the
+// msghdr.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassNotEnoughSpaceMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  std::vector<char> control(CMSG_SPACE(0) + 1);
+  msg.msg_control = &control[0];
+  msg.msg_controllen = control.size();
+
+  char received_data[sizeof(sent_data)];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_controllen, 0);
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+}
+
+// BasicThreeFDPassTruncationMsgCtrunc sends three FDs, but only provides enough
+// space to receive two of them. It then verifies that the MSG_CTRUNC flag is
+// set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, BasicThreeFDPassTruncationMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair1 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  auto pair2 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  auto pair3 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  int sent_fds[] = {pair1->second_fd(), pair2->second_fd(), pair3->second_fd()};
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendFDs(sockets->first_fd(), sent_fds, 3, sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  std::vector<char> control(CMSG_SPACE(2 * sizeof(int)));
+  msg.msg_control = &control[0];
+  msg.msg_controllen = control.size();
+
+  char received_data[sizeof(sent_data)];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(2 * sizeof(int)));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
+}
+
+// BasicFDPassUnalignedRecv starts off by sending a single FD just like
+// BasicFDPass. The difference is that when calling recvmsg, the length of the
+// receive data is only aligned on a 4 byte boundry instead of the normal 8.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassUnalignedRecv) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvSingleFDUnaligned(
+      sockets->second_fd(), &fd, received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
+}
+
+// BasicFDPassUnalignedRecvNoMsgTrunc sends one FD and only provides enough
+// space to receive just it. (Normally the minimum amount of space one would
+// provide would be enough space for two FDs.) It then verifies that the
+// MSG_CTRUNC flag is not set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, BasicFDPassUnalignedRecvNoMsgTrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(sizeof(int)) - sizeof(int)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_flags, 0);
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
+}
+
+// BasicTwoFDPassUnalignedRecvTruncationMsgTrunc sends two FDs, but only
+// provides enough space to receive one of them. It then verifies that the
+// MSG_CTRUNC flag is set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, BasicTwoFDPassUnalignedRecvTruncationMsgTrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  int sent_fds[] = {pair->first_fd(), pair->second_fd()};
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendFDs(sockets->first_fd(), sent_fds, 2, sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  // CMSG_SPACE rounds up to two FDs, we only want one.
+  char control[CMSG_SPACE(sizeof(int)) - sizeof(int)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
+}
+
+TEST_P(UnixSocketPairCmsgTest, ConcurrentBasicFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  int sockfd1 = sockets->first_fd();
+  auto recv_func = [sockfd1, sent_data]() {
+    char received_data[20];
+    int fd = -1;
+    RecvSingleFD(sockfd1, &fd, received_data, sizeof(received_data));
+    ASSERT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+    char buf[20];
+    ASSERT_THAT(ReadFd(fd, buf, sizeof(buf)),
+                SyscallSucceedsWithValue(sizeof(buf)));
+    ASSERT_THAT(WriteFd(fd, buf, sizeof(buf)),
+                SyscallSucceedsWithValue(sizeof(buf)));
+  };
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->second_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  ScopedThread t(recv_func);
+
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+  ASSERT_THAT(WriteFd(pair->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  char received_data[20];
+  ASSERT_THAT(ReadFd(pair->first_fd(), received_data, sizeof(received_data)),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  t.Join();
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+// FDPassNoRecv checks that the control message can be safely ignored by using
+// read(2) instead of recvmsg(2).
+TEST_P(UnixSocketPairCmsgTest, FDPassNoRecv) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  // Read while ignoring the passed FD.
+  char received_data[20];
+  ASSERT_THAT(
+      ReadFd(sockets->second_fd(), received_data, sizeof(received_data)),
+      SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  // Check that the socket still works for reads and writes.
+  ASSERT_NO_FATAL_FAILURE(
+      TransferTest(sockets->first_fd(), sockets->second_fd()));
+}
+
+// FDPassInterspersed1 checks that sent control messages cannot be read before
+// their associated data has been read.
+TEST_P(UnixSocketPairCmsgTest, FDPassInterspersed1) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char written_data[20];
+  RandomizeBuffer(written_data, sizeof(written_data));
+
+  ASSERT_THAT(WriteFd(sockets->first_fd(), written_data, sizeof(written_data)),
+              SyscallSucceedsWithValue(sizeof(written_data)));
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  // Check that we don't get a control message, but do get the data.
+  char received_data[20];
+  RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data));
+  EXPECT_EQ(0, memcmp(written_data, received_data, sizeof(written_data)));
+}
+
+// FDPassInterspersed2 checks that sent control messages cannot be read after
+// their assocated data has been read while ignoring the control message by
+// using read(2) instead of recvmsg(2).
+TEST_P(UnixSocketPairCmsgTest, FDPassInterspersed2) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char written_data[20];
+  RandomizeBuffer(written_data, sizeof(written_data));
+  ASSERT_THAT(WriteFd(sockets->first_fd(), written_data, sizeof(written_data)),
+              SyscallSucceedsWithValue(sizeof(written_data)));
+
+  char received_data[20];
+  ASSERT_THAT(
+      ReadFd(sockets->second_fd(), received_data, sizeof(received_data)),
+      SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+  EXPECT_EQ(0, memcmp(written_data, received_data, sizeof(written_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassNotCoalesced) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data1[20];
+  RandomizeBuffer(sent_data1, sizeof(sent_data1));
+
+  auto pair1 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair1->second_fd(),
+                                       sent_data1, sizeof(sent_data1)));
+
+  char sent_data2[20];
+  RandomizeBuffer(sent_data2, sizeof(sent_data2));
+
+  auto pair2 =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair2->second_fd(),
+                                       sent_data2, sizeof(sent_data2)));
+
+  char received_data1[sizeof(sent_data1) + sizeof(sent_data2)];
+  int received_fd1 = -1;
+
+  RecvSingleFD(sockets->second_fd(), &received_fd1, received_data1,
+               sizeof(received_data1), sizeof(sent_data1));
+
+  EXPECT_EQ(0, memcmp(sent_data1, received_data1, sizeof(sent_data1)));
+  TransferTest(pair1->first_fd(), pair1->second_fd());
+
+  char received_data2[sizeof(sent_data1) + sizeof(sent_data2)];
+  int received_fd2 = -1;
+
+  RecvSingleFD(sockets->second_fd(), &received_fd2, received_data2,
+               sizeof(received_data2), sizeof(sent_data2));
+
+  EXPECT_EQ(0, memcmp(sent_data2, received_data2, sizeof(sent_data2)));
+  TransferTest(pair2->first_fd(), pair2->second_fd());
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassPeek) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char peek_data[20];
+  int peek_fd = -1;
+  PeekSingleFD(sockets->second_fd(), &peek_fd, peek_data, sizeof(peek_data));
+  EXPECT_EQ(0, memcmp(sent_data, peek_data, sizeof(sent_data)));
+  TransferTest(peek_fd, pair->first_fd());
+  EXPECT_THAT(close(peek_fd), SyscallSucceeds());
+
+  char received_data[20];
+  int received_fd = -1;
+  RecvSingleFD(sockets->second_fd(), &received_fd, received_data,
+               sizeof(received_data));
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+  TransferTest(received_fd, pair->first_fd());
+  EXPECT_THAT(close(received_fd), SyscallSucceeds());
+}
+
+TEST_P(UnixSocketPairCmsgTest, BasicCredPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+  EXPECT_EQ(sent_creds.pid, received_creds.pid);
+  EXPECT_EQ(sent_creds.uid, received_creds.uid);
+  EXPECT_EQ(sent_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, SendNullCredsBeforeSoPassCredRecvEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds {
+    0, 65534, 65534
+  };
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, SendNullCredsAfterSoPassCredRecvEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  SetSoPassCred(sockets->second_fd());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds;
+  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, SendNullCredsBeforeSoPassCredSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->first_fd());
+
+  char received_data[20];
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest, SendNullCredsAfterSoPassCredSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  SetSoPassCred(sockets->first_fd());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest,
+       SendNullCredsBeforeSoPassCredRecvEndAfterSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  SetSoPassCred(sockets->first_fd());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendNullCmsg(sockets->first_fd(), sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds;
+  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, WriteBeforeSoPassCredRecvEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds {
+    0, 65534, 65534
+  };
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, WriteAfterSoPassCredRecvEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  SetSoPassCred(sockets->second_fd());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  char received_data[20];
+
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds;
+  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, WriteBeforeSoPassCredSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  SetSoPassCred(sockets->first_fd());
+
+  char received_data[20];
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest, WriteAfterSoPassCredSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  SetSoPassCred(sockets->first_fd());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  char received_data[20];
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest, WriteBeforeSoPassCredRecvEndAfterSendEnd) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  SetSoPassCred(sockets->first_fd());
+
+  ASSERT_THAT(WriteFd(sockets->first_fd(), sent_data, sizeof(sent_data)),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+
+  struct ucred received_creds;
+  ASSERT_NO_FATAL_FAILURE(RecvCreds(sockets->second_fd(), &received_creds,
+                                    received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds;
+  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+}
+
+TEST_P(UnixSocketPairCmsgTest, CredPassTruncated) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(0) + sizeof(pid_t)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  EXPECT_EQ(msg.msg_controllen, sizeof(control));
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
+
+  pid_t pid = 0;
+  memcpy(&pid, CMSG_DATA(cmsg), sizeof(pid));
+  EXPECT_EQ(pid, sent_creds.pid);
+}
+
+// CredPassNoMsgCtrunc passes a full set of credentials. It then verifies that
+// receiving the full set does not result in MSG_CTRUNC being set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, CredPassNoMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(sizeof(struct ucred))];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  // The control message should not be truncated.
+  EXPECT_EQ(msg.msg_flags, 0);
+  EXPECT_EQ(msg.msg_controllen, sizeof(control));
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(struct ucred)));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
+}
+
+// CredPassNoSpaceMsgCtrunc passes a full set of credentials. It then receives
+// the data without providing space for any credentials and verifies that
+// MSG_CTRUNC is set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, CredPassNoSpaceMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(0)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  // The control message should be truncated.
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+  EXPECT_EQ(msg.msg_controllen, sizeof(control));
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
+}
+
+// CredPassTruncatedMsgCtrunc passes a full set of credentials. It then receives
+// the data while providing enough space for only the first field of the
+// credentials and verifies that MSG_CTRUNC is set in the msghdr.
+TEST_P(UnixSocketPairCmsgTest, CredPassTruncatedMsgCtrunc) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(0) + sizeof(pid_t)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[sizeof(sent_data)] = {};
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  // The control message should be truncated.
+  EXPECT_EQ(msg.msg_flags, MSG_CTRUNC);
+  EXPECT_EQ(msg.msg_controllen, sizeof(control));
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
+}
+
+TEST_P(UnixSocketPairCmsgTest, SoPassCred) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  int opt;
+  socklen_t optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_FALSE(opt);
+
+  optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_FALSE(opt);
+
+  SetSoPassCred(sockets->first_fd());
+
+  optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_TRUE(opt);
+
+  optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_FALSE(opt);
+
+  int zero = 0;
+  EXPECT_THAT(setsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &zero,
+                         sizeof(zero)),
+              SyscallSucceeds());
+
+  optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->first_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_FALSE(opt);
+
+  optLen = sizeof(opt);
+  EXPECT_THAT(
+      getsockopt(sockets->second_fd(), SOL_SOCKET, SO_PASSCRED, &opt, &optLen),
+      SyscallSucceeds());
+  EXPECT_FALSE(opt);
+}
+
+TEST_P(UnixSocketPairCmsgTest, NoDataCredPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct msghdr msg = {};
+
+  struct iovec iov;
+  iov.iov_base = sent_data;
+  iov.iov_len = sizeof(sent_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  char control[CMSG_SPACE(0)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_CREDENTIALS;
+  cmsg->cmsg_len = CMSG_LEN(0);
+
+  ASSERT_THAT(RetryEINTR(sendmsg)(sockets->first_fd(), &msg, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+TEST_P(UnixSocketPairCmsgTest, NoPassCred) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  ASSERT_NO_FATAL_FAILURE(
+      SendCreds(sockets->first_fd(), sent_creds, sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+
+  ASSERT_NO_FATAL_FAILURE(
+      RecvNoCmsg(sockets->second_fd(), received_data, sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+}
+
+TEST_P(UnixSocketPairCmsgTest, CredAndFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  struct ucred sent_creds;
+
+  ASSERT_THAT(sent_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(sent_creds.gid = getgid(), SyscallSucceeds());
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendCredsAndFD(sockets->first_fd(), sent_creds,
+                                         pair->second_fd(), sent_data,
+                                         sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+  struct ucred received_creds;
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
+                                         &fd, received_data,
+                                         sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  EXPECT_EQ(sent_creds.pid, received_creds.pid);
+  EXPECT_EQ(sent_creds.uid, received_creds.uid);
+  EXPECT_EQ(sent_creds.gid, received_creds.gid);
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassBeforeSoPassCred) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  SetSoPassCred(sockets->second_fd());
+
+  char received_data[20];
+  struct ucred received_creds;
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
+                                         &fd, received_data,
+                                         sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds {
+    0, 65534, 65534
+  };
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassAfterSoPassCred) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  SetSoPassCred(sockets->second_fd());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  struct ucred received_creds;
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvCredsAndFD(sockets->second_fd(), &received_creds,
+                                         &fd, received_data,
+                                         sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  struct ucred want_creds;
+  ASSERT_THAT(want_creds.pid = getpid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.uid = getuid(), SyscallSucceeds());
+  ASSERT_THAT(want_creds.gid = getgid(), SyscallSucceeds());
+
+  EXPECT_EQ(want_creds.pid, received_creds.pid);
+  EXPECT_EQ(want_creds.uid, received_creds.uid);
+  EXPECT_EQ(want_creds.gid, received_creds.gid);
+
+  ASSERT_NO_FATAL_FAILURE(TransferTest(fd, pair->first_fd()));
+}
+
+TEST_P(UnixSocketPairCmsgTest, CloexecDroppedWhenFDPassed) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair = ASSERT_NO_ERRNO_AND_VALUE(
+      UnixDomainSocketPair(SOCK_SEQPACKET | SOCK_CLOEXEC).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  char received_data[20];
+  int fd = -1;
+  ASSERT_NO_FATAL_FAILURE(RecvSingleFD(sockets->second_fd(), &fd, received_data,
+                                       sizeof(received_data)));
+
+  EXPECT_THAT(fcntl(fd, F_GETFD), SyscallSucceedsWithValue(0));
+}
+
+TEST_P(UnixSocketPairCmsgTest, CloexecRecvFDPass) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(sizeof(int))];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  struct iovec iov;
+  char received_data[20];
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, MSG_CMSG_CLOEXEC),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
+  ASSERT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
+
+  int fd = -1;
+  memcpy(&fd, CMSG_DATA(cmsg), sizeof(int));
+
+  EXPECT_THAT(fcntl(fd, F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassAfterSoPassCredWithoutCredSpace) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  SetSoPassCred(sockets->second_fd());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  char control[CMSG_LEN(0)];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[20];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  EXPECT_EQ(msg.msg_controllen, sizeof(control));
+
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, sizeof(control));
+  EXPECT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  EXPECT_EQ(cmsg->cmsg_type, SCM_CREDENTIALS);
+}
+
+// This test will validate that MSG_CTRUNC as an input flag to recvmsg will
+// not appear as an output flag on the control message when truncation doesn't
+// happen.
+TEST_P(UnixSocketPairCmsgTest, MsgCtruncInputIsNoop) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  char control[CMSG_SPACE(sizeof(int)) /* we're passing a single fd */];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  struct iovec iov;
+  char received_data[20];
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, MSG_CTRUNC),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+  struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
+  ASSERT_NE(cmsg, nullptr);
+  ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(int)));
+  ASSERT_EQ(cmsg->cmsg_level, SOL_SOCKET);
+  ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);
+
+  // Now we should verify that MSG_CTRUNC wasn't set as an output flag.
+  EXPECT_EQ(msg.msg_flags & MSG_CTRUNC, 0);
+}
+
+TEST_P(UnixSocketPairCmsgTest, FDPassAfterSoPassCredWithoutCredHeaderSpace) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[20];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+
+  auto pair =
+      ASSERT_NO_ERRNO_AND_VALUE(UnixDomainSocketPair(SOCK_SEQPACKET).Create());
+
+  SetSoPassCred(sockets->second_fd());
+
+  ASSERT_NO_FATAL_FAILURE(SendSingleFD(sockets->first_fd(), pair->second_fd(),
+                                       sent_data, sizeof(sent_data)));
+
+  struct msghdr msg = {};
+  char control[CMSG_LEN(0) / 2];
+  msg.msg_control = control;
+  msg.msg_controllen = sizeof(control);
+
+  char received_data[20];
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, 0),
+              SyscallSucceedsWithValue(sizeof(received_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+  EXPECT_EQ(msg.msg_controllen, 0);
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor
diff --git a/test/syscalls/linux/socket_unix_cmsg.h b/test/syscalls/linux/socket_unix_cmsg.h
new file mode 100644
index 000000000..431606903
--- /dev/null
+++ b/test/syscalls/linux/socket_unix_cmsg.h
@@ -0,0 +1,30 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef GVISOR_TEST_SYSCALLS_LINUX_SOCKET_UNIX_CMSG_H_
+#define GVISOR_TEST_SYSCALLS_LINUX_SOCKET_UNIX_CMSG_H_
+
+#include "test/syscalls/linux/socket_test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+// Test fixture for tests that apply to pairs of connected unix sockets about
+// control messages.
+using UnixSocketPairCmsgTest = SocketPairTest;
+
+}  // namespace testing
+}  // namespace gvisor
+
+#endif  // GVISOR_TEST_SYSCALLS_LINUX_SOCKET_UNIX_CMSG_H_
diff --git a/test/syscalls/linux/socket_unix_pair.cc b/test/syscalls/linux/socket_unix_pair.cc
index bacfc11e4..411fb4518 100644
--- a/test/syscalls/linux/socket_unix_pair.cc
+++ b/test/syscalls/linux/socket_unix_pair.cc
@@ -16,6 +16,7 @@
 
 #include "test/syscalls/linux/socket_test_util.h"
 #include "test/syscalls/linux/socket_unix.h"
+#include "test/syscalls/linux/socket_unix_cmsg.h"
 #include "test/syscalls/linux/unix_domain_socket_test_util.h"
 #include "test/util/test_util.h"
 
@@ -33,5 +34,9 @@ INSTANTIATE_TEST_SUITE_P(
     AllUnixDomainSockets, UnixSocketPairTest,
     ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
 
+INSTANTIATE_TEST_SUITE_P(
+    AllUnixDomainSockets, UnixSocketPairCmsgTest,
+    ::testing::ValuesIn(IncludeReversals(GetSocketPairs())));
+
 }  // namespace testing
 }  // namespace gvisor