[PATCH 5.10.y] mptcp: sched: check both directions for backup

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

commit b6a66e521a2032f7fcba2af5a9bcbaeaa19b7ca3 upstream.

The 'mptcp_subflow_context' structure has two items related to the
backup flags:

 - 'backup': the subflow has been marked as backup by the other peer

 - 'request_bkup': the backup flag has been set by the host

Before this patch, the scheduler was only looking at the 'backup' flag.
That can make sense in some cases, but it looks like that's not what we
wanted for the general use, because either the path-manager was setting
both of them when sending an MP_PRIO, or the receiver was duplicating
the 'backup' flag in the subflow request.

Note that the use of these two flags in the path-manager are going to be
fixed in the next commits, but this change here is needed not to modify
the behaviour.

Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests")
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>
[ Conflicts in protocol.c, because the context has changed in commit
  3ce0852c86b9 ("mptcp: enforce HoL-blocking estimation") and in commit
  33d41c9cd74c ("mptcp: more accurate timeout"), which are not in this
  version. This commit is unrelated to this modification.
  Note that the tracepoint is not in this version, see commit
  e10a98920976 ("mptcp: add tracepoint in mptcp_subflow_get_send"). ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a36493bbf895..a343b3077458 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1124,11 +1124,13 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
 		send_info[i].ratio = -1;
 	}
 	mptcp_for_each_subflow(msk, subflow) {
+		bool backup = subflow->backup || subflow->request_bkup;
+
 		ssk =  mptcp_subflow_tcp_sock(subflow);
 		if (!mptcp_subflow_active(subflow))
 			continue;
 
-		nr_active += !subflow->backup;
+		nr_active += !backup;
 		*sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
 		if (!sk_stream_memory_free(subflow->tcp_sock))
 			continue;
@@ -1139,9 +1141,9 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
 
 		ratio = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32,
 				pace);
-		if (ratio < send_info[subflow->backup].ratio) {
-			send_info[subflow->backup].ssk = ssk;
-			send_info[subflow->backup].ratio = ratio;
+		if (ratio < send_info[backup].ratio) {
+			send_info[backup].ssk = ssk;
+			send_info[backup].ratio = ratio;
 		}
 	}
 
-- 
2.45.2