diff mbox series

[net-next,3/3] mptcp: ignore unsupported msg flags

Message ID 6254a6cfbb7269d0833be8aa07cbde1fd51a158c.1618502178.git.pabeni@redhat.com
State Accepted, archived
Commit faf109acd95974b79de5dbfd8303b054ee04737e
Delegated to: Matthieu Baerts
Headers show
Series mptcp: improve MSG_* flags handling | expand

Commit Message

Paolo Abeni April 15, 2021, 4:02 p.m. UTC 
Currently mptcp_sendmsg() fails with EOPNOTSUPP if the
user-space provides some unsupported flag. That is unexpected
and may foul existing applications migrated to MPTCP, which
expect a different behavior.

Change the mentioned function to silently ignore the unsupported
flags except MSG_FASTOPEN. This is the only flags currently not
supported by MPTCP with user-space visible side-effects.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/162
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v1 -> v2:
 - bail on MSG_FASTOPEN only

Note: this will conflict with the pending MSG_PEEK changes, with
hopefully simple resolution
---
 net/mptcp/protocol.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e6d1c293a615..04cb937630f6 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1614,8 +1614,12 @@  static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	int ret = 0;
 	long timeo;
 
-	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
-		return -EOPNOTSUPP;
+	/* we don't support FASTOPEN yet */
+	if (msg->msg_flags & MSG_FASTOPEN)
+		return -ENOTSUPP;
+
+	/* silently ignore everything else */
+	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL;
 
 	mptcp_lock_sock(sk, __mptcp_wmem_reserve(sk, min_t(size_t, 1 << 20, len)));
 
@@ -1951,9 +1955,6 @@  static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	if (unlikely(flags & MSG_ERRQUEUE))
 		return inet_recv_error(sk, msg, len, addr_len);
 
-	if (msg->msg_flags & ~(MSG_WAITALL | MSG_DONTWAIT))
-		return -EOPNOTSUPP;
-
 	mptcp_lock_sock(sk, __mptcp_splice_receive_queue(sk));
 	if (unlikely(sk->sk_state == TCP_LISTEN)) {
 		copied = -ENOTCONN;