Cleanup host UDS support

This change fixes several issues with the fsgofer host UDS support. Notably, it
adds support for SOCK_SEQPACKET and SOCK_DGRAM sockets [1]. It also fixes
unsafe use of unet.Socket, which could cause a panic if Socket.FD is called
when err != nil, and calls to Socket.FD with nothing to prevent the garbage
collector from destroying and closing the socket.

A set of tests is added to exercise host UDS access. This required extracting
most of the syscall test runner into a library that can be used by custom
tests.

Updates #235
Updates #1003

[1] N.B. SOCK_DGRAM sockets are likely not particularly useful, as a server can
only reply to a client that binds first. We don't allow bind, so these are
unlikely to be used.

PiperOrigin-RevId: 275558502

3 files changed, 191 insertions, 0 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 84a8eb76c..cf4c63b40 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -480,6 +480,21 @@ cc_binary(
 )
 
 cc_binary(
+    name = "connect_external_test",
+    testonly = 1,
+    srcs = ["connect_external.cc"],
+    linkstatic = 1,
+    deps = [
+        ":socket_test_util",
+        "//test/util:file_descriptor",
+        "//test/util:fs_util",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_binary(
     name = "creat_test",
     testonly = 1,
     srcs = ["creat.cc"],
diff --git a/test/syscalls/linux/accept_bind.cc b/test/syscalls/linux/accept_bind.cc
index 1122ea240..328192a05 100644
--- a/test/syscalls/linux/accept_bind.cc
+++ b/test/syscalls/linux/accept_bind.cc
@@ -140,6 +140,18 @@ TEST_P(AllSocketPairTest, Connect) {
               SyscallSucceeds());
 }
 
+TEST_P(AllSocketPairTest, ConnectNonListening) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  ASSERT_THAT(bind(sockets->first_fd(), sockets->first_addr(),
+                   sockets->first_addr_size()),
+              SyscallSucceeds());
+
+  ASSERT_THAT(connect(sockets->second_fd(), sockets->first_addr(),
+                      sockets->first_addr_size()),
+              SyscallFailsWithErrno(ECONNREFUSED));
+}
+
 TEST_P(AllSocketPairTest, ConnectToFilePath) {
   auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
 
diff --git a/test/syscalls/linux/connect_external.cc b/test/syscalls/linux/connect_external.cc
new file mode 100644
index 000000000..98032ac19
--- /dev/null
+++ b/test/syscalls/linux/connect_external.cc
@@ -0,0 +1,164 @@
+// Copyright 2019 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 <errno.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+
+#include <string>
+#include <tuple>
+
+#include "gtest/gtest.h"
+#include "gtest/gtest.h"
+#include "test/syscalls/linux/socket_test_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/fs_util.h"
+#include "test/util/test_util.h"
+
+// This file contains tests specific to connecting to host UDS managed outside
+// the sandbox / test.
+//
+// A set of ultity sockets will be created externally in $TEST_UDS_TREE and
+// $TEST_UDS_ATTACH_TREE for these tests to interact with.
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+struct ProtocolSocket {
+  int protocol;
+  std::string name;
+};
+
+// Parameter is (socket root dir, ProtocolSocket).
+using GoferStreamSeqpacketTest =
+    ::testing::TestWithParam<std::tuple<std::string, ProtocolSocket>>;
+
+// Connect to a socket and verify that write/read work.
+//
+// An "echo" socket doesn't work for dgram sockets because our socket is
+// unnamed. The server thus has no way to reply to us.
+TEST_P(GoferStreamSeqpacketTest, Echo) {
+  std::string env;
+  ProtocolSocket proto;
+  std::tie(env, proto) = GetParam();
+
+  char *val = getenv(env.c_str());
+  ASSERT_NE(val, nullptr);
+  std::string root(val);
+
+  FileDescriptor sock =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_UNIX, proto.protocol, 0));
+
+  std::string socket_path = JoinPath(root, proto.name, "echo");
+
+  struct sockaddr_un addr = {};
+  addr.sun_family = AF_UNIX;
+  memcpy(addr.sun_path, socket_path.c_str(), socket_path.length());
+
+  ASSERT_THAT(connect(sock.get(), reinterpret_cast<struct sockaddr *>(&addr),
+                      sizeof(addr)),
+              SyscallSucceeds());
+
+  constexpr int kBufferSize = 64;
+  char send_buffer[kBufferSize];
+  memset(send_buffer, 'a', sizeof(send_buffer));
+
+  ASSERT_THAT(WriteFd(sock.get(), send_buffer, sizeof(send_buffer)),
+              SyscallSucceedsWithValue(sizeof(send_buffer)));
+
+  char recv_buffer[kBufferSize];
+  ASSERT_THAT(ReadFd(sock.get(), recv_buffer, sizeof(recv_buffer)),
+              SyscallSucceedsWithValue(sizeof(recv_buffer)));
+  ASSERT_EQ(0, memcmp(send_buffer, recv_buffer, sizeof(send_buffer)));
+}
+
+// It is not possible to connect to a bound but non-listening socket.
+TEST_P(GoferStreamSeqpacketTest, NonListening) {
+  std::string env;
+  ProtocolSocket proto;
+  std::tie(env, proto) = GetParam();
+
+  char *val = getenv(env.c_str());
+  ASSERT_NE(val, nullptr);
+  std::string root(val);
+
+  FileDescriptor sock =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_UNIX, proto.protocol, 0));
+
+  std::string socket_path = JoinPath(root, proto.name, "nonlistening");
+
+  struct sockaddr_un addr = {};
+  addr.sun_family = AF_UNIX;
+  memcpy(addr.sun_path, socket_path.c_str(), socket_path.length());
+
+  ASSERT_THAT(connect(sock.get(), reinterpret_cast<struct sockaddr *>(&addr),
+                      sizeof(addr)),
+              SyscallFailsWithErrno(ECONNREFUSED));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    StreamSeqpacket, GoferStreamSeqpacketTest,
+    ::testing::Combine(
+        // Test access via standard path and attach point.
+        ::testing::Values("TEST_UDS_TREE", "TEST_UDS_ATTACH_TREE"),
+        ::testing::Values(ProtocolSocket{SOCK_STREAM, "stream"},
+                          ProtocolSocket{SOCK_SEQPACKET, "seqpacket"})));
+
+// Parameter is socket root dir.
+using GoferDgramTest = ::testing::TestWithParam<std::string>;
+
+// Connect to a socket and verify that write works.
+//
+// An "echo" socket doesn't work for dgram sockets because our socket is
+// unnamed. The server thus has no way to reply to us.
+TEST_P(GoferDgramTest, Null) {
+  std::string env = GetParam();
+  char *val = getenv(env.c_str());
+  ASSERT_NE(val, nullptr);
+  std::string root(val);
+
+  FileDescriptor sock =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_UNIX, SOCK_DGRAM, 0));
+
+  std::string socket_path = JoinPath(root, "dgram/null");
+
+  struct sockaddr_un addr = {};
+  addr.sun_family = AF_UNIX;
+  memcpy(addr.sun_path, socket_path.c_str(), socket_path.length());
+
+  ASSERT_THAT(connect(sock.get(), reinterpret_cast<struct sockaddr *>(&addr),
+                      sizeof(addr)),
+              SyscallSucceeds());
+
+  constexpr int kBufferSize = 64;
+  char send_buffer[kBufferSize];
+  memset(send_buffer, 'a', sizeof(send_buffer));
+
+  ASSERT_THAT(WriteFd(sock.get(), send_buffer, sizeof(send_buffer)),
+              SyscallSucceedsWithValue(sizeof(send_buffer)));
+}
+
+INSTANTIATE_TEST_SUITE_P(Dgram, GoferDgramTest,
+                         // Test access via standard path and attach point.
+                         ::testing::Values("TEST_UDS_TREE",
+                                           "TEST_UDS_ATTACH_TREE"));
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor