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Message-ID: <512682CF.4000609@gmail.com>
Date: Thu, 21 Feb 2013 15:25:51 -0500
From: Vlad Yasevich <vyasevich@...il.com>
To: "Roberts, Lee A." <lee.roberts@...com>
CC: "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] sctp: fix association hangs due to partial delivery
errors
On 02/21/2013 11:45 AM, Roberts, Lee A. 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_retrieve_partial() and sctp_ulpq_retrieve_first(),
> correct message reassembly logic for SCTP partial delivery.
> Change logic to ensure that as much data as possible is sent
> with the initial partial delivery and that following partial
> deliveries contain all available data.
>
> In sctp_ulpq_partial_delivery(), attempt partial delivery only
> if the data on the head of the reassembly queue is at or before
> the cumulative TSN ACK point.
>
> In sctp_ulpq_renege(), adjust logic to enter partial delivery
> only if the incoming chunk remains on the reassembly queue
> after processing by sctp_ulpq_tail_data(). If the incoming
> chunk has been delivered and data remains on the reassembly
> queue, attempt to drain the queue. Remove call to
> sctp_tsnmap_mark(), as this is handled correctly in call to
> sctp_ulpq_tail_data().
>
> Patch applies to linux-3.8 kernel.
>
> Signed-off-by: Lee A. Roberts <lee.roberts@...com>
Ok, we still have the weirdness of when partial deliver is started and
that can be another patch. This looks better. I am still not crazy
about all the checking of the TSNs at the head of the reassembly queue,
but this is better then before.
I really might be better to re-work the the return value from
sctp_ulpq_tail_data(). If we can return 1 if EOR was set, we can remove
the TSN check in sctp_ulpq_renege(). It would convert that code to
something like
retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
if (retval <= 0)
sctp_ulpq_partial_delivery(ulpq, chunk, gfp);
else if (retval > 0)
sctp_ulpq_reasm_drain(ulpq);
Just a suggestion.
-vlad
> ---
> net/sctp/ulpqueue.c | 53 +++++++++++++++++++++++++++++++++++-------
> 1 file changed, 45 insertions(+), 8 deletions(-)
>
> diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-SCTP+3/net/sctp/ulpqueue.c linux-3.8-SCTP+4/net/sctp/ulpqueue.c
> --- linux-3.8-SCTP+3/net/sctp/ulpqueue.c 2013-02-21 07:55:32.817713326 -0700
> +++ linux-3.8-SCTP+4/net/sctp/ulpqueue.c 2013-02-21 08:07:41.562212475 -0700
> @@ -540,14 +540,19 @@ static struct sctp_ulpevent *sctp_ulpq_r
> ctsn = cevent->tsn;
>
> switch (cevent->msg_flags & SCTP_DATA_FRAG_MASK) {
> + case SCTP_DATA_FIRST_FRAG:
> + if (!first_frag)
> + return NULL;
> + goto done;
> case SCTP_DATA_MIDDLE_FRAG:
> if (!first_frag) {
> first_frag = pos;
> next_tsn = ctsn + 1;
> last_frag = pos;
> - } else if (next_tsn == ctsn)
> + } else if (next_tsn == ctsn) {
> next_tsn++;
> - else
> + last_frag = pos;
> + } else
> goto done;
> break;
> case SCTP_DATA_LAST_FRAG:
> @@ -651,6 +656,14 @@ static struct sctp_ulpevent *sctp_ulpq_r
> } else
> goto done;
> break;
> +
> + case SCTP_DATA_LAST_FRAG:
> + if (!first_frag)
> + return NULL;
> + else
> + goto done;
> + break;
> +
> default:
> return NULL;
> }
> @@ -1025,16 +1038,28 @@ void sctp_ulpq_partial_delivery(struct s
> struct sctp_ulpevent *event;
> struct sctp_association *asoc;
> struct sctp_sock *sp;
> + __u32 ctsn;
> + struct sk_buff *skb;
>
> asoc = ulpq->asoc;
> sp = sctp_sk(asoc->base.sk);
>
> /* If the association is already in Partial Delivery mode
> - * we have noting to do.
> + * we have nothing to do.
> */
> if (ulpq->pd_mode)
> return;
>
> + /* Data must be at or below the Cumulative TSN ACK Point to
> + * start partial delivery.
> + */
> + skb = skb_peek(&asoc->ulpq.reasm);
> + if (skb != NULL) {
> + ctsn = sctp_skb2event(skb)->tsn;
> + if (!TSN_lte(ctsn, sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map)))
> + return;
> + }
> +
> /* If the user enabled fragment interleave socket option,
> * multiple associations can enter partial delivery.
> * Otherwise, we can only enter partial delivery if the
> @@ -1057,6 +1082,7 @@ void sctp_ulpq_renege(struct sctp_ulpq *
> gfp_t gfp)
> {
> struct sctp_association *asoc;
> + struct sk_buff *skb;
> __u16 needed, freed;
>
> asoc = ulpq->asoc;
> @@ -1077,12 +1103,23 @@ void sctp_ulpq_renege(struct sctp_ulpq *
> }
> /* If able to free enough room, accept this chunk. */
> if (chunk && (freed >= needed)) {
> - __u32 tsn;
> + __u32 tsn, ctsn;
> tsn = ntohl(chunk->subh.data_hdr->tsn);
> - sctp_tsnmap_mark(&asoc->peer.tsn_map, tsn, chunk->transport);
> - sctp_ulpq_tail_data(ulpq, chunk, gfp);
> -
> - sctp_ulpq_partial_delivery(ulpq, gfp);
> + if (sctp_ulpq_tail_data(ulpq, chunk, gfp) == 0) {
> + /*
> + * Enter partial delivery if chunk is still on
> + * reassembly queue; otherwise, drain the queue.
> + */
> + skb = skb_peek(&ulpq->reasm);
> + if (skb != NULL) {
> + ctsn = sctp_skb2event(skb)->tsn;
> + if (TSN_lte(ctsn, tsn))
> + sctp_ulpq_partial_delivery(ulpq, chunk,
> + gfp);
> + else
> + sctp_ulpq_reasm_drain(ulpq);
> + }
> + }
> }
>
> sk_mem_reclaim(asoc->base.sk);
> --
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