netdev - Re: [PATCH 3/4] sctp: fix association hangs due to errors when reneging events from the ordering queue

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Date:	Wed, 27 Feb 2013 08:53:04 -0500
From:	Vlad Yasevich <vyasevich@...il.com>
To:	"Lee A. Roberts" <lee.roberts@...com>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH 3/4] sctp: fix association hangs due to errors when reneging
 events from the ordering queue

On 02/26/2013 09:36 AM, Lee A. Roberts wrote:
> From: "Lee A. Roberts" <lee.roberts@...com>
>
> 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(), events being reneged from the
> ordering queue may correspond to multiple TSNs.  Identify
> all affected packets; sum freed space and renege from the
> tsnmap.
>
> Signed-off-by: Lee A. Roberts <lee.roberts@...com>

Acked-by: Vlad Yasevich <vyasevich@...il.com>

-vlad

> ---
>   net/sctp/ulpqueue.c |   26 ++++++++++++++++++++++----
>   1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
> index 63afddc..f221fbb 100644
> --- a/net/sctp/ulpqueue.c
> +++ b/net/sctp/ulpqueue.c
> @@ -962,8 +962,8 @@ static __u16 sctp_ulpq_renege_list(struct sctp_ulpq *ulpq,
>   		struct sk_buff_head *list, __u16 needed)
>   {
>   	__u16 freed = 0;
> -	__u32 tsn;
> -	struct sk_buff *skb;
> +	__u32 tsn, last_tsn;
> +	struct sk_buff *skb, *flist, *last;
>   	struct sctp_ulpevent *event;
>   	struct sctp_tsnmap *tsnmap;
>
> @@ -977,10 +977,28 @@ static __u16 sctp_ulpq_renege_list(struct sctp_ulpq *ulpq,
>   		if (TSN_lte(tsn, sctp_tsnmap_get_ctsn(tsnmap)))
>   			break;
>
> -		__skb_unlink(skb, list);
> +		/* Events in ordering queue may have multiple fragments
> +		 * corresponding to additional TSNs.  Sum the total
> +		 * freed space; find the last TSN.
> +		 */
>   		freed += skb_headlen(skb);
> +		flist = skb_shinfo(skb)->frag_list;
> +		for (last = flist; flist; flist = flist->next) {
> +			last = flist;
> +			freed += skb_headlen(last);
> +		}
> +		if (last)
> +			last_tsn = sctp_skb2event(last)->tsn;
> +		else
> +			last_tsn = tsn;
> +
> +		/* Unlink the event, then renege all applicable TSNs. */
> +		__skb_unlink(skb, list);
>   		sctp_ulpevent_free(event);
> -		sctp_tsnmap_renege(tsnmap, tsn);
> +		while (TSN_lte(tsn, last_tsn)) {
> +			sctp_tsnmap_renege(tsnmap, tsn);
> +			tsn++;
> +		}
>   		if (freed >= needed)
>   			return freed;
>   	}
>

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