Commit 21c02e82 authored by Matthieu Baerts (NGI0)'s avatar Matthieu Baerts (NGI0) Committed by Jakub Kicinski
Browse files

mptcp: only inc MPJoinAckHMacFailure for HMAC failures 



Recently, during a debugging session using local MPTCP connections, I
noticed MPJoinAckHMacFailure was not zero on the server side. The
counter was in fact incremented when the PM rejected new subflows,
because the 'subflow' limit was reached.

The fix is easy, simply dissociating the two cases: only the HMAC
validation check should increase MPTCP_MIB_JOINACKMAC counter.

Fixes: 4cf8b7e4 ("subflow: introduce and use mptcp_can_accept_new_subflow()")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarGeliang Tang <geliang@kernel.org>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250407-net-mptcp-hmac-failure-mib-v1-1-3c9ecd0a3a50@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 445e99bd

net/mptcp/subflow.c

+6 −2
Original line number Diff line number Diff line
@@ -899,13 +899,17 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, 
				goto dispose_child;

			}



			if (!subflow_hmac_valid(req, &mp_opt) ||

			    !mptcp_can_accept_new_subflow(subflow_req->msk)) {

			if (!subflow_hmac_valid(req, &mp_opt)) {

				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);

				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);

				goto dispose_child;

			}



			if (!mptcp_can_accept_new_subflow(owner)) {

				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);

				goto dispose_child;

			}



			/* move the msk reference ownership to the subflow */

			subflow_req->msk = NULL;

			ctx->conn = (struct sock *)owner;