Add support for TCP_USER_TIMEOUT option.

The implementation follows the linux behavior where specifying
a TCP_USER_TIMEOUT will cause the resend timer to honor the
user specified timeout rather than the default rto based timeout.

Further it alters when connections are timedout due to keepalive
failures. It does not alter the behavior of when keepalives are
sent. This is as per the linux behavior.

PiperOrigin-RevId: 285099795

1 files changed, 25 insertions, 0 deletions

diff --git a/test/syscalls/linux/tcp_socket.cc b/test/syscalls/linux/tcp_socket.cc
index 99863b0ed..c503f3568 100644
--- a/test/syscalls/linux/tcp_socket.cc
+++ b/test/syscalls/linux/tcp_socket.cc
@@ -1175,6 +1175,31 @@ TEST_P(SimpleTcpSocketTest, SetMaxSegFailsForInvalidMSSValues) {
   }
 }
 
+TEST_P(SimpleTcpSocketTest, SetTCPUserTimeout) {
+  FileDescriptor s =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(GetParam(), SOCK_STREAM, IPPROTO_TCP));
+
+  {
+    constexpr int kTCPUserTimeout = -1;
+    EXPECT_THAT(setsockopt(s.get(), IPPROTO_TCP, TCP_USER_TIMEOUT,
+                           &kTCPUserTimeout, sizeof(kTCPUserTimeout)),
+                SyscallFailsWithErrno(EINVAL));
+  }
+
+  // kTCPUserTimeout is in milliseconds.
+  constexpr int kTCPUserTimeout = 100;
+  ASSERT_THAT(setsockopt(s.get(), IPPROTO_TCP, TCP_USER_TIMEOUT,
+                         &kTCPUserTimeout, sizeof(kTCPUserTimeout)),
+              SyscallSucceedsWithValue(0));
+  int get = -1;
+  socklen_t get_len = sizeof(get);
+  ASSERT_THAT(
+      getsockopt(s.get(), IPPROTO_TCP, TCP_USER_TIMEOUT, &get, &get_len),
+      SyscallSucceedsWithValue(0));
+  EXPECT_EQ(get_len, sizeof(get));
+  EXPECT_EQ(get, kTCPUserTimeout);
+}
+
 INSTANTIATE_TEST_SUITE_P(AllInetTests, SimpleTcpSocketTest,
                          ::testing::Values(AF_INET, AF_INET6));