From fe7fe52a884163e50b44031fc0ce4bd0d4af65b9 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Thu, 20 May 2021 16:46:13 +0200 Subject: [PATCH] mptcp: always parse mptcp options for MPC reqsk In subflow_syn_recv_sock() we currently skip options parsing for OoO packet, given that such packets may not carry the relevant MPC option. If the peer generates an MPC+data TSO packet and some of the early segments are lost or get reorder, we server will ignore the peer key, causing transient, unexpected fallback to TCP. The solution is always parsing the incoming MPTCP options, and do the fallback only for in-order packets. This actually cleans the existing code a bit. Reported-by: Matthieu Baerts Fixes: d22f4988ffec ("mptcp: process MP_CAPABLE data option") Signed-off-by: Paolo Abeni --- net/mptcp/subflow.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 2f13d795c2fc70..442c162dd60bbc 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -633,21 +633,20 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, /* if the sk is MP_CAPABLE, we try to fetch the client key */ if (subflow_req->mp_capable) { - if (TCP_SKB_CB(skb)->seq != subflow_req->ssn_offset + 1) { - /* here we can receive and accept an in-window, - * out-of-order pkt, which will not carry the MP_CAPABLE - * opt even on mptcp enabled paths - */ - goto create_msk; - } - + /* we can receive and accept an in-window, out-of-order pkt, + * which may not carry the MP_CAPABLE opt even on mptcp enabled + * paths: always try to extract the peer key, and fallback + * for packets missing it. + * Even OoO DSS packets coming legitly after dropped or + * reordered MPC will cause fallback, but we don't have other + * options. + */ mptcp_get_options(sk, skb, &mp_opt); if (!mp_opt.mp_capable) { fallback = true; goto create_child; } -create_msk: new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req); if (!new_msk) fallback = true;