From 1a0c8883274ed5797bda815d83735395ab412cda Mon Sep 17 00:00:00 2001 From: Davide Caratti Date: Fri, 29 Mar 2024 13:08:52 +0100 Subject: [PATCH] mptcp: don't account accept() of non-MPC client as fallback to TCP commit 7a1b3490f47e88ec4cbde65f1a77a0f4bc972282 upstream. Current MPTCP servers increment MPTcpExtMPCapableFallbackACK when they accept non-MPC connections. As reported by Christoph, this is "surprising" because the counter might become greater than MPTcpExtMPCapableSYNRX. MPTcpExtMPCapableFallbackACK counter's name suggests it should only be incremented when a connection was seen using MPTCP options, then a fallback to TCP has been done. Let's do that by incrementing it when the subflow context of an inbound MPC connection attempt is dropped. Also, update mptcp_connect.sh kselftest, to ensure that the above MIB does not increment in case a pure TCP client connects to a MPTCP server. Fixes: fc518953bc9c ("mptcp: add and use MIB counter infrastructure") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/449 Signed-off-by: Davide Caratti Reviewed-by: Mat Martineau Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://lore.kernel.org/r/20240329-upstream-net-20240329-fallback-mib-v1-1-324a8981da48@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 3 --- net/mptcp/subflow.c | 3 +++ 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index adbe6350f..6be7e7592 100755 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2218,9 +2218,6 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err, __MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK); local_bh_enable(); - } else { - MPTCP_INC_STATS(sock_net(sk), - MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); } out: diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 607519246..276fe9f44 100755 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -595,6 +595,9 @@ create_child: if (fallback_is_fatal) goto dispose_child; + if (fallback) + SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); + subflow_drop_ctx(child); goto out; }