From 21c02e8272bc95ba0dd44943665c669029b42760 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Mon, 7 Apr 2025 20:26:32 +0200 Subject: [PATCH 1/2] 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; From 6767698cf9c144c8d4c72925e9a1cd2cbc031d25 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Mon, 7 Apr 2025 20:26:33 +0200 Subject: [PATCH 2/2] selftests: mptcp: validate MPJoin HMacFailure counters The parent commit fixes an issue around these counters where one of them -- MPJoinAckHMacFailure -- was wrongly incremented in some cases. This makes sure the counter is always 0. It should be incremented only in case of corruption, or a wrong implementation, which should not be the case in these selftests. 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-v1-2-3c9ecd0a3a50@kernel.org Signed-off-by: Jakub Kicinski --- .../testing/selftests/net/mptcp/mptcp_join.sh | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh index 13a3b68181ee..befa66f5a366 100755 --- a/tools/testing/selftests/net/mptcp/mptcp_join.sh +++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh @@ -1441,6 +1441,15 @@ chk_join_nr() fi fi + count=$(mptcp_lib_get_counter ${ns2} "MPTcpExtMPJoinSynAckHMacFailure") + if [ -z "$count" ]; then + rc=${KSFT_SKIP} + elif [ "$count" != "0" ]; then + rc=${KSFT_FAIL} + print_check "synack HMAC" + fail_test "got $count JOIN[s] synack HMAC failure expected 0" + fi + count=$(mptcp_lib_get_counter ${ns1} "MPTcpExtMPJoinAckRx") if [ -z "$count" ]; then rc=${KSFT_SKIP} @@ -1450,6 +1459,15 @@ chk_join_nr() fail_test "got $count JOIN[s] ack rx expected $ack_nr" fi + count=$(mptcp_lib_get_counter ${ns1} "MPTcpExtMPJoinAckHMacFailure") + if [ -z "$count" ]; then + rc=${KSFT_SKIP} + elif [ "$count" != "0" ]; then + rc=${KSFT_FAIL} + print_check "ack HMAC" + fail_test "got $count JOIN[s] ack HMAC failure expected 0" + fi + print_results "join Rx" ${rc} join_syn_tx="${join_syn_tx:-${syn_nr}}" \