mptcp: skip to next candidate if subflow has unacked data

[ Upstream commit 860975c6f80adae9d2c7654bde04a99dd28bc94f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 967ce9c..f56b2e3 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1648,8 +1648,11 @@ 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)