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Date: Fri, 29 Jun 2012 16:19:43 -0400
From: Vlad Yasevich <vyasevich@...il.com>
To: Neil Horman <nhorman@...driver.com>
CC: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
linux-sctp@...r.kernel.org
Subject: Re: [PATCH v5] sctp: be more restrictive in transport selection on
bundled sacks
On 06/29/2012 04:15 PM, Neil Horman wrote:
> It was noticed recently that when we send data on a transport, its possible that
> we might bundle a sack that arrived on a different transport. While this isn't
> a major problem, it does go against the SHOULD requirement in section 6.4 of RFC
> 2960:
>
> An endpoint SHOULD transmit reply chunks (e.g., SACK, HEARTBEAT ACK,
> etc.) to the same destination transport address from which it
> received the DATA or control chunk to which it is replying. This
> rule should also be followed if the endpoint is bundling DATA chunks
> together with the reply chunk.
>
> This patch seeks to correct that. It restricts the bundling of sack operations
> to only those transports which have moved the ctsn of the association forward
> since the last sack. By doing this we guarantee that we only bundle outbound
> saks on a transport that has received a chunk since the last sack. This brings
> us into stricter compliance with the RFC.
>
> Vlad had initially suggested that we strictly allow only sack bundling on the
> transport that last moved the ctsn forward. While this makes sense, I was
> concerned that doing so prevented us from bundling in the case where we had
> received chunks that moved the ctsn on multiple transports. In those cases, the
> RFC allows us to select any of the transports having received chunks to bundle
> the sack on. so I've modified the approach to allow for that, by adding a state
> variable to each transport that tracks weather it has moved the ctsn since the
> last sack. This I think keeps our behavior (and performance), close enough to
> our current profile that I think we can do this without a sysctl knob to
> enable/disable it.
>
> Signed-off-by: Neil Horman<nhorman@...driver.com>
> CC: Vlad Yaseivch<vyasevich@...il.com>
> CC: David S. Miller<davem@...emloft.net>
> CC: linux-sctp@...r.kernel.org
> Reported-by: Michele Baldessari<michele@...hat.com>
> Reported-by: sorin serban<sserban@...hat.com>
>
Thanks Neil. Looks good.
Acked-by: Vlad Yasevich <vyasevich@...il.com>
-vlad
> ---
> Change Notes:
> V2)
> * Removed unused variable as per Dave M. Request
> * Delayed rwnd adjustment until we are sure we will sack (Vlad Y.)
> V3)
> * Switched test to use pkt->transport rather than chunk->transport
> * Modified detection of sacka-able transport. Instead of just setting
> and clearning a flag, we now mark each transport and association with
> a sack generation tag. We increment the associations generation on
> every sack, and assign that generation tag to every transport that
> updates the ctsn. This prevents us from having to iterate over a for
> loop on every sack, which is much more scalable.
> V4)
> * Fixed up wrapping comment and logic
> V5)
> * Simplified wrap logic further per request from vlad
> ---
> include/net/sctp/structs.h | 4 ++++
> include/net/sctp/tsnmap.h | 3 ++-
> net/sctp/associola.c | 1 +
> net/sctp/output.c | 9 +++++++--
> net/sctp/sm_make_chunk.c | 17 +++++++++++++++++
> net/sctp/sm_sideeffect.c | 2 +-
> net/sctp/transport.c | 2 ++
> net/sctp/tsnmap.c | 6 +++++-
> net/sctp/ulpevent.c | 3 ++-
> net/sctp/ulpqueue.c | 2 +-
> 10 files changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index e4652fe..fecdf31 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -912,6 +912,9 @@ struct sctp_transport {
> /* Is this structure kfree()able? */
> malloced:1;
>
> + /* Has this transport moved the ctsn since we last sacked */
> + __u32 sack_generation;
> +
> struct flowi fl;
>
> /* This is the peer's IP address and port. */
> @@ -1584,6 +1587,7 @@ struct sctp_association {
> */
> __u8 sack_needed; /* Do we need to sack the peer? */
> __u32 sack_cnt;
> + __u32 sack_generation;
>
> /* These are capabilities which our peer advertised. */
> __u8 ecn_capable:1, /* Can peer do ECN? */
> diff --git a/include/net/sctp/tsnmap.h b/include/net/sctp/tsnmap.h
> index e7728bc..2c5d2b4 100644
> --- a/include/net/sctp/tsnmap.h
> +++ b/include/net/sctp/tsnmap.h
> @@ -117,7 +117,8 @@ void sctp_tsnmap_free(struct sctp_tsnmap *map);
> int sctp_tsnmap_check(const struct sctp_tsnmap *, __u32 tsn);
>
> /* Mark this TSN as seen. */
> -int sctp_tsnmap_mark(struct sctp_tsnmap *, __u32 tsn);
> +int sctp_tsnmap_mark(struct sctp_tsnmap *, __u32 tsn,
> + struct sctp_transport *trans);
>
> /* Mark this TSN and all lower as seen. */
> void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn);
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index 5bc9ab1..b16517e 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -271,6 +271,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a
> */
> asoc->peer.sack_needed = 1;
> asoc->peer.sack_cnt = 0;
> + asoc->peer.sack_generation = 1;
>
> /* Assume that the peer will tell us if he recognizes ASCONF
> * as part of INIT exchange.
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index f1b7d4b..0de6cd5 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -240,14 +240,19 @@ static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
> */
> if (sctp_chunk_is_data(chunk)&& !pkt->has_sack&&
> !pkt->has_cookie_echo) {
> - struct sctp_association *asoc;
> struct timer_list *timer;
> - asoc = pkt->transport->asoc;
> + struct sctp_association *asoc = pkt->transport->asoc;
> +
> timer =&asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
>
> /* If the SACK timer is running, we have a pending SACK */
> if (timer_pending(timer)) {
> struct sctp_chunk *sack;
> +
> + if (pkt->transport->sack_generation !=
> + pkt->transport->asoc->peer.sack_generation)
> + return retval;
> +
> asoc->a_rwnd = asoc->rwnd;
> sack = sctp_make_sack(asoc);
> if (sack) {
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index a85eeeb..6486cac 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -734,8 +734,10 @@ struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc)
> int len;
> __u32 ctsn;
> __u16 num_gabs, num_dup_tsns;
> + struct sctp_association *aptr = (struct sctp_association *)asoc;
> struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;
> struct sctp_gap_ack_block gabs[SCTP_MAX_GABS];
> + struct sctp_transport *trans;
>
> memset(gabs, 0, sizeof(gabs));
> ctsn = sctp_tsnmap_get_ctsn(map);
> @@ -805,6 +807,21 @@ struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc)
> sctp_addto_chunk(retval, sizeof(__u32) * num_dup_tsns,
> sctp_tsnmap_get_dups(map));
>
> + /*
> + * Once we have a sack generated, check to see what our sack
> + * generation is, if its 0, reset the transports to 0, and reset
> + * the association generation to 1
> + *
> + * The idea is that zero is never used as a valid generation for the
> + * association so no transport will match after a wrap event like this,
> + * Until the next sack
> + */
> + if (++aptr->peer.sack_generation == 0) {
> + list_for_each_entry(trans,&asoc->peer.transport_addr_list,
> + transports)
> + trans->sack_generation = 0;
> + aptr->peer.sack_generation = 1;
> + }
> nodata:
> return retval;
> }
> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> index c96d1a8..8716da1 100644
> --- a/net/sctp/sm_sideeffect.c
> +++ b/net/sctp/sm_sideeffect.c
> @@ -1268,7 +1268,7 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
> case SCTP_CMD_REPORT_TSN:
> /* Record the arrival of a TSN. */
> error = sctp_tsnmap_mark(&asoc->peer.tsn_map,
> - cmd->obj.u32);
> + cmd->obj.u32, NULL);
> break;
>
> case SCTP_CMD_REPORT_FWDTSN:
> diff --git a/net/sctp/transport.c b/net/sctp/transport.c
> index b026ba0..1dcceb6 100644
> --- a/net/sctp/transport.c
> +++ b/net/sctp/transport.c
> @@ -68,6 +68,8 @@ static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
> peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
> memset(&peer->saddr, 0, sizeof(union sctp_addr));
>
> + peer->sack_generation = 0;
> +
> /* From 6.3.1 RTO Calculation:
> *
> * C1) Until an RTT measurement has been made for a packet sent to the
> diff --git a/net/sctp/tsnmap.c b/net/sctp/tsnmap.c
> index f1e40ceb..b5fb7c4 100644
> --- a/net/sctp/tsnmap.c
> +++ b/net/sctp/tsnmap.c
> @@ -114,7 +114,8 @@ int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
>
>
> /* Mark this TSN as seen. */
> -int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn)
> +int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn,
> + struct sctp_transport *trans)
> {
> u16 gap;
>
> @@ -133,6 +134,9 @@ int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn)
> */
> map->max_tsn_seen++;
> map->cumulative_tsn_ack_point++;
> + if (trans)
> + trans->sack_generation =
> + trans->asoc->peer.sack_generation;
> map->base_tsn++;
> } else {
> /* Either we already have a gap, or about to record a gap, so
> diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
> index 8a84017..33d8947 100644
> --- a/net/sctp/ulpevent.c
> +++ b/net/sctp/ulpevent.c
> @@ -715,7 +715,8 @@ struct sctp_ulpevent *sctp_ulpevent_make_rcvmsg(struct sctp_association *asoc,
> * can mark it as received so the tsn_map is updated correctly.
> */
> if (sctp_tsnmap_mark(&asoc->peer.tsn_map,
> - ntohl(chunk->subh.data_hdr->tsn)))
> + ntohl(chunk->subh.data_hdr->tsn),
> + chunk->transport))
> goto fail_mark;
>
> /* First calculate the padding, so we don't inadvertently
> diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
> index f2d1de7..f5a6a4f 100644
> --- a/net/sctp/ulpqueue.c
> +++ b/net/sctp/ulpqueue.c
> @@ -1051,7 +1051,7 @@ void sctp_ulpq_renege(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
> if (chunk&& (freed>= needed)) {
> __u32 tsn;
> tsn = ntohl(chunk->subh.data_hdr->tsn);
> - sctp_tsnmap_mark(&asoc->peer.tsn_map, tsn);
> + sctp_tsnmap_mark(&asoc->peer.tsn_map, tsn, chunk->transport);
> sctp_ulpq_tail_data(ulpq, chunk, gfp);
>
> sctp_ulpq_partial_delivery(ulpq, chunk, gfp);
--
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