Add NETLINK_KOBJECT_UEVENT socket support

NETLINK_KOBJECT_UEVENT sockets send udev-style messages for device events.
gVisor doesn't have any device events, so our sockets don't need to do anything
once created.

systemd's device manager needs to be able to create one of these sockets. It
also wants to install a BPF filter on the socket. Since we'll never send any
messages, the filter would never be invoked, thus we just fake it out.

Fixes #1117
Updates #1119

PiperOrigin-RevId: 278405893

1 files changed, 153 insertions, 0 deletions

diff --git a/test/syscalls/linux/socket_netlink.cc b/test/syscalls/linux/socket_netlink.cc
new file mode 100644
index 000000000..4ec0fd4fa
--- /dev/null
+++ b/test/syscalls/linux/socket_netlink.cc
@@ -0,0 +1,153 @@
+// 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 <linux/netlink.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "gtest/gtest.h"
+#include "test/syscalls/linux/socket_test_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/test_util.h"
+
+// Tests for all netlink socket protocols.
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+// NetlinkTest parameter is the protocol to test.
+using NetlinkTest = ::testing::TestWithParam<int>;
+
+// Netlink sockets must be SOCK_DGRAM or SOCK_RAW.
+TEST_P(NetlinkTest, Types) {
+  const int protocol = GetParam();
+
+  EXPECT_THAT(socket(AF_NETLINK, SOCK_STREAM, protocol),
+              SyscallFailsWithErrno(ESOCKTNOSUPPORT));
+  EXPECT_THAT(socket(AF_NETLINK, SOCK_SEQPACKET, protocol),
+              SyscallFailsWithErrno(ESOCKTNOSUPPORT));
+  EXPECT_THAT(socket(AF_NETLINK, SOCK_RDM, protocol),
+              SyscallFailsWithErrno(ESOCKTNOSUPPORT));
+  EXPECT_THAT(socket(AF_NETLINK, SOCK_DCCP, protocol),
+              SyscallFailsWithErrno(ESOCKTNOSUPPORT));
+  EXPECT_THAT(socket(AF_NETLINK, SOCK_PACKET, protocol),
+              SyscallFailsWithErrno(ESOCKTNOSUPPORT));
+
+  int fd;
+  EXPECT_THAT(fd = socket(AF_NETLINK, SOCK_DGRAM, protocol), SyscallSucceeds());
+  EXPECT_THAT(close(fd), SyscallSucceeds());
+
+  EXPECT_THAT(fd = socket(AF_NETLINK, SOCK_RAW, protocol), SyscallSucceeds());
+  EXPECT_THAT(close(fd), SyscallSucceeds());
+}
+
+TEST_P(NetlinkTest, AutomaticPort) {
+  const int protocol = GetParam();
+
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_NETLINK, SOCK_RAW, protocol));
+
+  struct sockaddr_nl addr = {};
+  addr.nl_family = AF_NETLINK;
+
+  EXPECT_THAT(
+      bind(fd.get(), reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr)),
+      SyscallSucceeds());
+
+  socklen_t addrlen = sizeof(addr);
+  EXPECT_THAT(getsockname(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                          &addrlen),
+              SyscallSucceeds());
+  EXPECT_EQ(addrlen, sizeof(addr));
+  // This is the only netlink socket in the process, so it should get the PID as
+  // the port id.
+  //
+  // N.B. Another process could theoretically have explicitly reserved our pid
+  // as a port ID, but that is very unlikely.
+  EXPECT_EQ(addr.nl_pid, getpid());
+}
+
+// Calling connect automatically binds to an automatic port.
+TEST_P(NetlinkTest, ConnectBinds) {
+  const int protocol = GetParam();
+
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_NETLINK, SOCK_RAW, protocol));
+
+  struct sockaddr_nl addr = {};
+  addr.nl_family = AF_NETLINK;
+
+  EXPECT_THAT(connect(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                      sizeof(addr)),
+              SyscallSucceeds());
+
+  socklen_t addrlen = sizeof(addr);
+  EXPECT_THAT(getsockname(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                          &addrlen),
+              SyscallSucceeds());
+  EXPECT_EQ(addrlen, sizeof(addr));
+
+  // Each test is running in a pid namespace, so another process can explicitly
+  // reserve our pid as a port ID. In this case, a negative portid value will be
+  // set.
+  if (static_cast<pid_t>(addr.nl_pid) > 0) {
+    EXPECT_EQ(addr.nl_pid, getpid());
+  }
+
+  memset(&addr, 0, sizeof(addr));
+  addr.nl_family = AF_NETLINK;
+
+  // Connecting again is allowed, but keeps the same port.
+  EXPECT_THAT(connect(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                      sizeof(addr)),
+              SyscallSucceeds());
+
+  addrlen = sizeof(addr);
+  EXPECT_THAT(getsockname(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                          &addrlen),
+              SyscallSucceeds());
+  EXPECT_EQ(addrlen, sizeof(addr));
+  EXPECT_EQ(addr.nl_pid, getpid());
+}
+
+TEST_P(NetlinkTest, GetPeerName) {
+  const int protocol = GetParam();
+
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_NETLINK, SOCK_RAW, protocol));
+
+  struct sockaddr_nl addr = {};
+  socklen_t addrlen = sizeof(addr);
+
+  EXPECT_THAT(getpeername(fd.get(), reinterpret_cast<struct sockaddr*>(&addr),
+                          &addrlen),
+              SyscallSucceeds());
+
+  EXPECT_EQ(addrlen, sizeof(addr));
+  EXPECT_EQ(addr.nl_family, AF_NETLINK);
+  // Peer is the kernel if we didn't connect elsewhere.
+  EXPECT_EQ(addr.nl_pid, 0);
+}
+
+INSTANTIATE_TEST_SUITE_P(ProtocolTest, NetlinkTest,
+                         ::testing::Values(NETLINK_ROUTE,
+                                           NETLINK_KOBJECT_UEVENT));
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor