This is a note to let you know that I've just added the patch titled mptcp: relax check on MPC passive fallback to the 6.1-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: mptcp-relax-check-on-mpc-passive-fallback.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit fee42bb3059485302a427eff7d41c83295b24d11 Author: Paolo Abeni <pabeni@xxxxxxxxxx> Date: Tue Jan 16 18:18:47 2024 +0100 mptcp: relax check on MPC passive fallback [ Upstream commit c0f5aec28edf98906d28f08daace6522adf9ee7a ] While testing the blamed commit below, I was able to miss (!) packetdrill failures in the fastopen test-cases. On passive fastopen the child socket is created by incoming TCP MPC syn, allow for both MPC_SYN and MPC_ACK header. Fixes: 724b00c12957 ("mptcp: refine opt_mp_capable determination") Reviewed-by: Matthieu Baerts <matttbe@xxxxxxxxxx> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index f0ebf39db6cc..45d20e20cfc0 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -713,7 +713,8 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, * options. */ mptcp_get_options(skb, &mp_opt); - if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK)) + if (!(mp_opt.suboptions & + (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_ACK))) fallback = true; } else if (subflow_req->mp_join) {