mptcp: skip to next candidate if subflow has unacked data

In case a subflow path is blocked, MPTCP-level retransmit may not take
place anymore because such subflow is likely to have unacked data left
in its write queue.

Ignore subflows that have experienced loss and test next candidate.

Fixes: 3b1d6210a95773691 ("mptcp: implement and use MPTCP-level retransmission")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2d450865937d5336984d33eadfc5472bde0801d3..868c76cf0f150e182c8821b55e96d80cc2618ebf 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1726,8 +1726,11 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
                        continue;
 
                /* still data outstanding at TCP level?  Don't retransmit. */
-               if (!tcp_write_queue_empty(ssk))
+               if (!tcp_write_queue_empty(ssk)) {
+                       if (inet_csk(ssk)->icsk_ca_state >= TCP_CA_Loss)
+                               continue;
                        return NULL;
+               }
 
                if (subflow->backup) {
                        if (!backup)