From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 06f9a435b3aa12f4de6da91f11fdce8ce7b46205 ]
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.
Fixes: d22f4988ffec ("mptcp: process MP_CAPABLE data option") Reported-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Mat Martineau mathew.j.martineau@linux.intel.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 1936db3574d2..8878317b4386 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -608,21 +608,20 @@ 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(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;