net: sctp: confirm route during forward progress

This fix has been proposed originally by Vlad Yasevich. He says:

  When SCTP makes forward progress (receives a SACK that acks new chunks,
  renegs, or answeres 0-window probes) or when HB-ACK arrives, mark
  the route as confirmed so we don't unnecessarily send NUD probes.

Having a simple SCTP client/server that exchange data chunks every 1sec,
without this patch ARP requests are sent periodically every 40-60sec.
With this fix applied, an ARP request is only done once right at the
"session" beginning. Also, when clearing the related ARP cache entry
manually during the session, a new request is correctly done. I have
only "backported" this to net-next and tested that it works, so full
credit goes to Vlad.

Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index cb80a8e060b7..ef9e2bbc0f2f 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1334,6 +1334,7 @@ static void sctp_check_transmitted(struct sctp_outq *q,
         __u8 restart_timer = 0;
         int bytes_acked = 0;
         int migrate_bytes = 0;
+        bool forward_progress = false;
 
         sack_ctsn = ntohl(sack->cum_tsn_ack);
 
@@ -1400,6 +1401,7 @@ static void sctp_check_transmitted(struct sctp_outq *q,
                                 bytes_acked += sctp_data_size(tchunk);
                                 if (!tchunk->transport)
                                         migrate_bytes += sctp_data_size(tchunk);
+                                forward_progress = true;
                         }
 
                         if (TSN_lte(tsn, sack_ctsn)) {
@@ -1413,6 +1415,7 @@ static void sctp_check_transmitted(struct sctp_outq *q,
                                  * current RTO.
                                  */
                                 restart_timer = 1;
+                                forward_progress = true;
 
                                 if (!tchunk->tsn_gap_acked) {
                                         /*
@@ -1503,6 +1506,7 @@ static void sctp_check_transmitted(struct sctp_outq *q,
                          */
                         transport->error_count = 0;
                         transport->asoc->overall_error_count = 0;
+                        forward_progress = true;
 
                         /*
                          * While in SHUTDOWN PENDING, we may have started
@@ -1576,6 +1580,11 @@ static void sctp_check_transmitted(struct sctp_outq *q,
                                        jiffies + transport->rto))
                                 sctp_transport_hold(transport);
                 }
+
+                if (forward_progress) {
+                        if (transport->dst)
+                                dst_confirm(transport->dst);
+                }
         }
 
         list_splice(&tlist, transmitted_queue);