Re: [PATCH 2/4] sctp: fix association hangs due to reneging packetsbelow the cumulative TSN ACK point

[Vlad Yasevich]

On 02/21/2013 11:44 AM, Roberts, Lee A. wrote:
> From: Lee A. Roberts <lee.roberts@xxxxxx>
>
> Resolve SCTP association hangs observed during SCTP stress
> testing.  Observable symptoms include communications hangs
> with data being held in the association reassembly and/or lobby
> (ordering) queues.  Close examination of reassembly queue shows
> missing packets.
>
> In sctp_ulpq_renege_list(), do not renege packets below the
> cumulative TSN ACK point.
>
> Patch applies to linux-3.8 kernel.
>
> Signed-off-by: Lee A. Roberts <lee.roberts@xxxxxx>

Acked-by: Vlad Yasevich <vyasevich@xxxxxxxxx>

-vlad

> ---
>   net/sctp/ulpqueue.c |    9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-SCTP+1/net/sctp/ulpqueue.c linux-3.8-SCTP+2/net/sctp/ulpqueue.c
> --- linux-3.8-SCTP+1/net/sctp/ulpqueue.c	2013-02-18 16:58:34.000000000 -0700
> +++ linux-3.8-SCTP+2/net/sctp/ulpqueue.c	2013-02-21 07:39:40.888281496 -0700
> @@ -969,11 +969,16 @@ static __u16 sctp_ulpq_renege_list(struc
>
>   	tsnmap = &ulpq->asoc->peer.tsn_map;
>
> -	while ((skb = __skb_dequeue_tail(list)) != NULL) {
> -		freed += skb_headlen(skb);
> +	while ((skb = skb_peek_tail(list)) != NULL) {
>   		event = sctp_skb2event(skb);
>   		tsn = event->tsn;
>
> +		/* Don't renege below the Cumulative TSN ACK Point. */
> +		if (TSN_lte(tsn, sctp_tsnmap_get_ctsn(tsnmap)))
> +			break;
> +
> +		__skb_unlink(skb, list);
> +		freed += skb_headlen(skb);
>   		sctp_ulpevent_free(event);
>   		sctp_tsnmap_renege(tsnmap, tsn);
>   		if (freed >= needed)
> --
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