This is a note to let you know that I've just added the patch titled tcp: consistently disable header prediction for mptcp to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: tcp-consistently-disable-header-prediction-for-mptcp.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 71158bb1f2d2da61385c58fc1114e1a1c19984ba Mon Sep 17 00:00:00 2001 From: Paolo Abeni <pabeni@xxxxxxxxxx> Date: Wed, 30 Jun 2021 13:42:13 +0200 Subject: tcp: consistently disable header prediction for mptcp From: Paolo Abeni <pabeni@xxxxxxxxxx> commit 71158bb1f2d2da61385c58fc1114e1a1c19984ba upstream. 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 e1ff9e82e2ea ("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: e1ff9e82e2ea ("net: mptcp: improve fallback to TCP") Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/net/tcp.h | 4 ++++ 1 file changed, 4 insertions(+) --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -676,6 +676,10 @@ static inline u32 __tcp_set_rto(const st 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); Patches currently in stable-queue which might be from pabeni@xxxxxxxxxx are queue-5.10/tcp-consistently-disable-header-prediction-for-mptcp.patch