From 21c02e8272bc95ba0dd44943665c669029b42760 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Mon, 7 Apr 2025 20:26:32 +0200 Subject: [PATCH] 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: 4cf8b7e48a09 ("subflow: introduce and use mptcp_can_accept_new_subflow()") Cc: stable@vger.kernel.org Reviewed-by: Geliang Tang Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250407-net-mptcp-hmac-failure-mib-v1-1-3c9ecd0a3a50@kernel.org Signed-off-by: Jakub Kicinski --- net/mptcp/subflow.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 409bd415ef1d..24c2de1891bd 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -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;