mptcp: use MPJoinSynAckHMacFailure for SynAck HMAC failure

In subflow_finish_connect(), HMAC validation of the server's HMAC
in SYN/ACK + MP_JOIN increments MPTCP_MIB_JOINACKMAC ("HMAC was
wrong on ACK + MP_JOIN") on failure. The function processes the
SYN/ACK, not the ACK; the matching MPTCP_MIB_JOINSYNACKMAC counter
("HMAC was wrong on SYN/ACK + MP_JOIN") exists but is not
incremented anywhere in the tree.

The mirror site on the server, subflow_syn_recv_sock(), already
uses JOINACKMAC correctly for ACK HMAC failure. Use JOINSYNACKMAC
at the SYN/ACK validation site so each counter reflects the packet
whose HMAC actually failed.

Suggested-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Fixes: fc518953bc9c ("mptcp: add and use MIB counter infrastructure")
Cc: stable@vger.kernel.org
Signed-off-by: Shardul Bankar <shardul.b@mpiricsoftware.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260501-net-mptcp-misc-fixes-7-1-rc3-v1-1-b70118df778e@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index e2cb9d23e4a0b2fc5a46e641b53858ebd8d48895..bda6862264ca4aa1ab943f7066c7ee69d46aab7c 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -581,7 +581,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
                         subflow->backup);
 
                if (!subflow_thmac_valid(subflow)) {
-                       MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
+                       MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKMAC);
                        subflow->reset_reason = MPTCP_RST_EMPTCP;
                        goto do_reset;
                }