tcp: consistently disable header prediction for mptcp

The MPTCP receive path is hooked only into the TCP slow-path.
The DSS presence allows plain MPTCP traffic to hit that
consistently.

Since commit c5be4bc9a7f5 ("net: mptcp: improve fallback to TCP"),
when an MPTCP socket falls back to TCP, it can hit the TCP receive
fast-path, and delay or stop triggering the event notification.

Address the issue explicitly disabling the header prediction
for MPTCP sockets.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/200
Fixes: c5be4bc9a7f5 ("net: mptcp: improve fallback to TCP")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index e668f1bf780d3eccbe36fd2666d3653cd3f079d1..17df9b047ee46dabed8797246f99e1a2fd39c243 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -686,6 +686,10 @@ static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
 
 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
 {
+       /* mptcp hooks are only on the slow path */
+       if (sk_is_mptcp((struct sock *)tp))
+               return;
+
        tp->pred_flags = htonl((tp->tcp_header_len << 26) |
                               ntohl(TCP_FLAG_ACK) |
                               snd_wnd);