Make socketops reflect correct sndbuf value for host UDS.

Also skips a test if the setsockopt to increase send buffer did not result in an
increase. This is possible when the underlying socket is a host backed unix
domain socket as in such cases gVisor does not permit increasing SO_SNDBUF.

PiperOrigin-RevId: 358285158

2 files changed, 17 insertions, 2 deletions

diff --git a/pkg/sentry/socket/unix/transport/connectioned.go b/pkg/sentry/socket/unix/transport/connectioned.go
index 809c95429..b1967fc36 100644
--- a/pkg/sentry/socket/unix/transport/connectioned.go
+++ b/pkg/sentry/socket/unix/transport/connectioned.go
@@ -364,7 +364,9 @@ func (e *connectionedEndpoint) Connect(ctx context.Context, server BoundEndpoint
 		e.connected = ce
 		// Make sure the newly created connected endpoint's write queue is updated
 		// to reflect this endpoint's send buffer size.
-		e.connected.SetSendBufferSize(e.ops.GetSendBufferSize())
+		if bufSz := e.connected.SetSendBufferSize(e.ops.GetSendBufferSize()); bufSz != e.ops.GetSendBufferSize() {
+			e.ops.SetSendBufferSize(bufSz, false /* notify */)
+		}
 	}
 
 	return server.BidirectionalConnect(ctx, e, returnConnect)
diff --git a/test/syscalls/linux/socket_unix_seqpacket.cc b/test/syscalls/linux/socket_unix_seqpacket.cc
index eb373373d..d6e7031c0 100644
--- a/test/syscalls/linux/socket_unix_seqpacket.cc
+++ b/test/syscalls/linux/socket_unix_seqpacket.cc
@@ -91,7 +91,20 @@ TEST_P(SeqpacketUnixSocketPairTest, IncreasedSocketSendBufUnblocksWrites) {
       setsockopt(sock, SOL_SOCKET, SO_SNDBUF, &buf_size, sizeof(buf_size)),
       SyscallSucceeds());
 
-  // The send should succeed again.
+  // Skip test if the setsockopt didn't increase the sendbuf. This happens for
+  // tests where the socket is a host fd where gVisor does not permit increasing
+  // send buffer size.
+  int new_buf_size = 0;
+  buf_size_len = sizeof(new_buf_size);
+  ASSERT_THAT(
+      getsockopt(sock, SOL_SOCKET, SO_SNDBUF, &new_buf_size, &buf_size_len),
+      SyscallSucceeds());
+  if (IsRunningOnGvisor() && (new_buf_size <= buf_size)) {
+    GTEST_SKIP() << "Skipping test new send buffer size " << new_buf_size
+                 << " is the same as the value before setsockopt, "
+                 << " socket is probably a host backed socket." << std ::endl;
+  }
+  //  send should succeed again.
   ASSERT_THAT(RetryEINTR(send)(sock, buf.data(), buf.size(), 0),
               SyscallSucceeds());
 }