sctp: start t5 timer only when peer rwnd is 0 and local state is SHUTDOWN_PENDING

commit 8a0d19c5ed417c78d03f4e0fa7215e58c40896d8 upstream.

when A sends a data to B, then A close() and enter into SHUTDOWN_PENDING
state, if B neither claim his rwnd is 0 nor send SACK for this data, A
will keep retransmitting this data until t5 timeout, Max.Retrans times
can't work anymore, which is bad.

if B's rwnd is not 0, it should send abort after Max.Retrans times, only
when B's rwnd == 0 and A's retransmitting beyonds Max.Retrans times, A
will start t5 timer, which is also commit f8d960524328 ("sctp: Enforce
retransmission limit during shutdown") means, but it lacks the condition
peer rwnd == 0.

so fix it by adding a bit (zero_window_announced) in peer to record if
the last rwnd is 0. If it was, zero_window_announced will be set. and use
this bit to decide if start t5 timer when local.state is SHUTDOWN_PENDING.

Fixes: commit f8d960524328 ("sctp: Enforce retransmission limit during shutdown")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: change sack_needed to bitfield as done earlier upstream]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 4ea0ec64eadaf41cb94a6468c21a63c6668b0e2c..e60eb4036c0db896df0e98b95b44fc9d6209a7be 100644 (file)
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1587,7 +1587,8 @@ struct sctp_association {
                 *             : order.  When DATA chunks are out of order,
                 *             : SACK's are not delayed (see Section 6).
                 */
-               __u8    sack_needed;     /* Do we need to sack the peer? */
+               __u8    sack_needed:1,     /* Do we need to sack the peer? */
+                       zero_window_announced:1;
                __u32   sack_cnt;
 
                /* These are capabilities which our peer advertised.  */

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 3dd7207d33ad259c0b05527f75945b0a2a93803f..7b285462c88e06b109363974c5a4af1074d78a19 100644 (file)
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1265,6 +1265,7 @@ int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
         */
 
        sack_a_rwnd = ntohl(sack->a_rwnd);
+       asoc->peer.zero_window_announced = !sack_a_rwnd;
        outstanding = q->outstanding_bytes;
 
        if (outstanding < sack_a_rwnd)

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index a6a300630af4f1617354a04db30da6ca40e9bbf8..5de7200f07a705a4c1481737955264e6ae3e74c4 100644 (file)
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -5299,7 +5299,8 @@ sctp_disposition_t sctp_sf_do_6_3_3_rtx(const struct sctp_endpoint *ep,
        SCTP_INC_STATS(SCTP_MIB_T3_RTX_EXPIREDS);
 
        if (asoc->overall_error_count >= asoc->max_retrans) {
-               if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING) {
+               if (asoc->peer.zero_window_announced &&
+                   asoc->state == SCTP_STATE_SHUTDOWN_PENDING) {
                        /*
                         * We are here likely because the receiver had its rwnd
                         * closed for a while and we have not been able to