6.13-stable review patch. If anyone has any objections, please let me know.
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From: Matthieu Baerts (NGI0) matttbe@kernel.org
commit e598d8981fd34470b78a1ae777dbf131b15d5bf2 upstream.
The Fixes commit mentioned this:
An MPTCP firewall blackhole can be detected if the following SYN retransmission after a fallback to "plain" TCP is accepted.
But in fact, this blackhole was detected if any following SYN retransmissions after a fallback to TCP was accepted.
That's because 'mptcp_subflow_early_fallback()' will set 'request_mptcp' to 0, and 'mpc_drop' will never be reset to 0 after.
This is an issue, because some not so unusual situations might cause the kernel to detect a false-positive blackhole, e.g. a client trying to connect to a server while the network is not ready yet, causing a few SYN retransmissions, before reaching the end server.
Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/ctrl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/mptcp/ctrl.c +++ b/net/mptcp/ctrl.c @@ -405,9 +405,9 @@ void mptcp_active_detect_blackhole(struc MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEACTIVEDROP); subflow->mpc_drop = 1; mptcp_subflow_early_fallback(mptcp_sk(subflow->conn), subflow); - } else { - subflow->mpc_drop = 0; } + } else if (ssk->sk_state == TCP_SYN_SENT) { + subflow->mpc_drop = 0; } }