[PATCH net 0/2] sctp: shrink stream outq in the right place

[PATCH net 0/2] sctp: shrink stream outq in the right place

[Xin Long]

Patch 1 is an improvement, and Patch 2 is a bug fix.

Xin Long (2):
  sctp: shrink stream outq only when new outcnt < old outcnt
  sctp: shrink stream outq when fails to do addstream reconf

 net/sctp/stream.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

-- 
2.1.0

[PATCH net 1/2] sctp: shrink stream outq only when new outcnt < old outcnt

[Xin Long]

It's not necessary to go list_for_each for outq->out_chunk_list
when new outcnt >= old outcnt, as no chunk with higher sid than
new (outcnt - 1) exists in the outqueue.

While at it, also move the list_for_each code in a new function
sctp_stream_shrink_out(), which will be used in the next patch.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sctp/stream.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 67f7e71..4f87693 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -22,17 +22,11 @@
 #include <net/sctp/sm.h>
 #include <net/sctp/stream_sched.h>
 
-/* Migrates chunks from stream queues to new stream queues if needed,
- * but not across associations. Also, removes those chunks to streams
- * higher than the new max.
- */
-static void sctp_stream_outq_migrate(struct sctp_stream *stream,
-				     struct sctp_stream *new, __u16 outcnt)
+static void sctp_stream_shrink_out(struct sctp_stream *stream, __u16 outcnt)
 {
 	struct sctp_association *asoc;
 	struct sctp_chunk *ch, *temp;
 	struct sctp_outq *outq;
-	int i;
 
 	asoc = container_of(stream, struct sctp_association, stream);
 	outq = &asoc->outqueue;
@@ -56,6 +50,19 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
 
 		sctp_chunk_free(ch);
 	}
+}
+
+/* Migrates chunks from stream queues to new stream queues if needed,
+ * but not across associations. Also, removes those chunks to streams
+ * higher than the new max.
+ */
+static void sctp_stream_outq_migrate(struct sctp_stream *stream,
+				     struct sctp_stream *new, __u16 outcnt)
+{
+	int i;
+
+	if (stream->outcnt > outcnt)
+		sctp_stream_shrink_out(stream, outcnt);
 
 	if (new) {
 		/* Here we actually move the old ext stuff into the new
-- 
2.1.0

[PATCH net 2/2] sctp: shrink stream outq when fails to do addstream reconf

[Xin Long]

When adding a stream with stream reconf, the new stream firstly is in
CLOSED state but new out chunks can still be enqueued. Then once gets
the confirmation from the peer, the state will change to OPEN.

However, if the peer denies, it needs to roll back the stream. But when
doing that, it only sets the stream outcnt back, and the chunks already
in the new stream don't get purged. It caused these chunks can still be
dequeued in sctp_outq_dequeue_data().

As its stream is still in CLOSE, the chunk will be enqueued to the head
again by sctp_outq_head_data(). This chunk will never be sent out, and
the chunks after it can never be dequeued. The assoc will be 'hung' in
a dead loop of sending this chunk.

To fix it, this patch is to purge these chunks already in the new
stream by calling sctp_stream_shrink_out() when failing to do the
addstream reconf.

Fixes: 11ae76e67a17 ("sctp: implement receiver-side procedures for the Reconf Response Parameter")
Reported-by: Ying Xu <yinxu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sctp/stream.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 4f87693..bda2536 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -1044,11 +1044,13 @@ struct sctp_chunk *sctp_process_strreset_resp(
 		nums = ntohs(addstrm->number_of_streams);
 		number = stream->outcnt - nums;
 
-		if (result = SCTP_STRRESET_PERFORMED)
+		if (result = SCTP_STRRESET_PERFORMED) {
 			for (i = number; i < stream->outcnt; i++)
 				SCTP_SO(stream, i)->state = SCTP_STREAM_OPEN;
-		else
+		} else {
+			sctp_stream_shrink_out(stream, number);
 			stream->outcnt = number;
+		}
 
 		*evp = sctp_ulpevent_make_stream_change_event(asoc, flags,
 			0, nums, GFP_ATOMIC);
-- 
2.1.0

Re: [PATCH net 0/2] sctp: shrink stream outq in the right place

[Marcelo Ricardo Leitner]

On Wed, Jul 22, 2020 at 11:52:10PM +0800, Xin Long wrote:
> Patch 1 is an improvement, and Patch 2 is a bug fix.
> 
> Xin Long (2):
>   sctp: shrink stream outq only when new outcnt < old outcnt
>   sctp: shrink stream outq when fails to do addstream reconf

Nice changelogs, thanks.

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Re: [PATCH net 0/2] sctp: shrink stream outq in the right place

[David Miller]

From: Xin Long <lucien.xin@gmail.com>
Date: Wed, 22 Jul 2020 23:52:10 +0800

> Patch 1 is an improvement, and Patch 2 is a bug fix.

Series applied, and queued up for -stable, thank you.