From 987858e5d026d355535b34f17c6ceeb1d71ccf75 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 23 Apr 2021 11:17:07 -0700 Subject: [PATCH] mptcp: ignore unsupported msg flags 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 Signed-off-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/protocol.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index ae08c563c712..a996dd5bb0c2 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1614,9 +1614,13 @@ 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)) + /* we don't support FASTOPEN yet */ + if (msg->msg_flags & MSG_FASTOPEN) return -EOPNOTSUPP; + /* 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))); timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); @@ -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;