linux/net/sctp/transport.c
Vlad Yasevich 06ad391919 [SCTP] Don't disable PMTU discovery when mtu is small
Right now, when we receive a mtu estimate smaller then minim
threshold in the ICMP message, we disable the path mtu discovery
on the transport.  This leads to the never increasing sctp fragmentation
point even when the real path mtu has increased.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
2007-06-13 20:44:42 +00:00

600 lines
18 KiB
C

/* SCTP kernel reference Implementation
* Copyright (c) 1999-2000 Cisco, Inc.
* Copyright (c) 1999-2001 Motorola, Inc.
* Copyright (c) 2001-2003 International Business Machines Corp.
* Copyright (c) 2001 Intel Corp.
* Copyright (c) 2001 La Monte H.P. Yarroll
*
* This file is part of the SCTP kernel reference Implementation
*
* This module provides the abstraction for an SCTP tranport representing
* a remote transport address. For local transport addresses, we just use
* union sctp_addr.
*
* The SCTP reference implementation is free software;
* you can redistribute it and/or modify it under the terms of
* the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* The SCTP reference implementation is distributed in the hope that it
* will be useful, but WITHOUT ANY WARRANTY; without even the implied
* ************************
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU CC; see the file COPYING. If not, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Please send any bug reports or fixes you make to the
* email address(es):
* lksctp developers <lksctp-developers@lists.sourceforge.net>
*
* Or submit a bug report through the following website:
* http://www.sf.net/projects/lksctp
*
* Written or modified by:
* La Monte H.P. Yarroll <piggy@acm.org>
* Karl Knutson <karl@athena.chicago.il.us>
* Jon Grimm <jgrimm@us.ibm.com>
* Xingang Guo <xingang.guo@intel.com>
* Hui Huang <hui.huang@nokia.com>
* Sridhar Samudrala <sri@us.ibm.com>
* Ardelle Fan <ardelle.fan@intel.com>
*
* Any bugs reported given to us we will try to fix... any fixes shared will
* be incorporated into the next SCTP release.
*/
#include <linux/types.h>
#include <linux/random.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
/* 1st Level Abstractions. */
/* Initialize a new transport from provided memory. */
static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
const union sctp_addr *addr,
gfp_t gfp)
{
/* Copy in the address. */
peer->ipaddr = *addr;
peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
peer->asoc = NULL;
peer->dst = NULL;
memset(&peer->saddr, 0, sizeof(union sctp_addr));
/* From 6.3.1 RTO Calculation:
*
* C1) Until an RTT measurement has been made for a packet sent to the
* given destination transport address, set RTO to the protocol
* parameter 'RTO.Initial'.
*/
peer->rtt = 0;
peer->rto = msecs_to_jiffies(sctp_rto_initial);
peer->rttvar = 0;
peer->srtt = 0;
peer->rto_pending = 0;
peer->last_time_heard = jiffies;
peer->last_time_used = jiffies;
peer->last_time_ecne_reduced = jiffies;
peer->init_sent_count = 0;
peer->param_flags = SPP_HB_DISABLE |
SPP_PMTUD_ENABLE |
SPP_SACKDELAY_ENABLE;
peer->hbinterval = 0;
/* Initialize the default path max_retrans. */
peer->pathmaxrxt = sctp_max_retrans_path;
peer->error_count = 0;
INIT_LIST_HEAD(&peer->transmitted);
INIT_LIST_HEAD(&peer->send_ready);
INIT_LIST_HEAD(&peer->transports);
/* Set up the retransmission timer. */
init_timer(&peer->T3_rtx_timer);
peer->T3_rtx_timer.function = sctp_generate_t3_rtx_event;
peer->T3_rtx_timer.data = (unsigned long)peer;
/* Set up the heartbeat timer. */
init_timer(&peer->hb_timer);
peer->hb_timer.function = sctp_generate_heartbeat_event;
peer->hb_timer.data = (unsigned long)peer;
/* Initialize the 64-bit random nonce sent with heartbeat. */
get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
atomic_set(&peer->refcnt, 1);
peer->dead = 0;
peer->malloced = 0;
/* Initialize the state information for SFR-CACC */
peer->cacc.changeover_active = 0;
peer->cacc.cycling_changeover = 0;
peer->cacc.next_tsn_at_change = 0;
peer->cacc.cacc_saw_newack = 0;
return peer;
}
/* Allocate and initialize a new transport. */
struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
gfp_t gfp)
{
struct sctp_transport *transport;
transport = t_new(struct sctp_transport, gfp);
if (!transport)
goto fail;
if (!sctp_transport_init(transport, addr, gfp))
goto fail_init;
transport->malloced = 1;
SCTP_DBG_OBJCNT_INC(transport);
return transport;
fail_init:
kfree(transport);
fail:
return NULL;
}
/* This transport is no longer needed. Free up if possible, or
* delay until it last reference count.
*/
void sctp_transport_free(struct sctp_transport *transport)
{
transport->dead = 1;
/* Try to delete the heartbeat timer. */
if (del_timer(&transport->hb_timer))
sctp_transport_put(transport);
/* Delete the T3_rtx timer if it's active.
* There is no point in not doing this now and letting
* structure hang around in memory since we know
* the tranport is going away.
*/
if (timer_pending(&transport->T3_rtx_timer) &&
del_timer(&transport->T3_rtx_timer))
sctp_transport_put(transport);
sctp_transport_put(transport);
}
/* Destroy the transport data structure.
* Assumes there are no more users of this structure.
*/
static void sctp_transport_destroy(struct sctp_transport *transport)
{
SCTP_ASSERT(transport->dead, "Transport is not dead", return);
if (transport->asoc)
sctp_association_put(transport->asoc);
sctp_packet_free(&transport->packet);
dst_release(transport->dst);
kfree(transport);
SCTP_DBG_OBJCNT_DEC(transport);
}
/* Start T3_rtx timer if it is not already running and update the heartbeat
* timer. This routine is called every time a DATA chunk is sent.
*/
void sctp_transport_reset_timers(struct sctp_transport *transport)
{
/* RFC 2960 6.3.2 Retransmission Timer Rules
*
* R1) Every time a DATA chunk is sent to any address(including a
* retransmission), if the T3-rtx timer of that address is not running
* start it running so that it will expire after the RTO of that
* address.
*/
if (!timer_pending(&transport->T3_rtx_timer))
if (!mod_timer(&transport->T3_rtx_timer,
jiffies + transport->rto))
sctp_transport_hold(transport);
/* When a data chunk is sent, reset the heartbeat interval. */
if (!mod_timer(&transport->hb_timer,
sctp_transport_timeout(transport)))
sctp_transport_hold(transport);
}
/* This transport has been assigned to an association.
* Initialize fields from the association or from the sock itself.
* Register the reference count in the association.
*/
void sctp_transport_set_owner(struct sctp_transport *transport,
struct sctp_association *asoc)
{
transport->asoc = asoc;
sctp_association_hold(asoc);
}
/* Initialize the pmtu of a transport. */
void sctp_transport_pmtu(struct sctp_transport *transport)
{
struct dst_entry *dst;
dst = transport->af_specific->get_dst(NULL, &transport->ipaddr, NULL);
if (dst) {
transport->pathmtu = dst_mtu(dst);
dst_release(dst);
} else
transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}
/* this is a complete rip-off from __sk_dst_check
* the cookie is always 0 since this is how it's used in the
* pmtu code
*/
static struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
{
struct dst_entry *dst = t->dst;
if (dst && dst->obsolete && dst->ops->check(dst, 0) == NULL) {
dst_release(t->dst);
t->dst = NULL;
return NULL;
}
return dst;
}
void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
{
struct dst_entry *dst;
if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
printk(KERN_WARNING "%s: Reported pmtu %d too low, "
"using default minimum of %d\n",
__FUNCTION__, pmtu,
SCTP_DEFAULT_MINSEGMENT);
/* Use default minimum segment size and disable
* pmtu discovery on this transport.
*/
t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
} else {
t->pathmtu = pmtu;
}
dst = sctp_transport_dst_check(t);
if (dst)
dst->ops->update_pmtu(dst, pmtu);
}
/* Caches the dst entry and source address for a transport's destination
* address.
*/
void sctp_transport_route(struct sctp_transport *transport,
union sctp_addr *saddr, struct sctp_sock *opt)
{
struct sctp_association *asoc = transport->asoc;
struct sctp_af *af = transport->af_specific;
union sctp_addr *daddr = &transport->ipaddr;
struct dst_entry *dst;
dst = af->get_dst(asoc, daddr, saddr);
if (saddr)
memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
else
af->get_saddr(asoc, dst, daddr, &transport->saddr);
transport->dst = dst;
if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
return;
}
if (dst) {
transport->pathmtu = dst_mtu(dst);
/* Initialize sk->sk_rcv_saddr, if the transport is the
* association's active path for getsockname().
*/
if (asoc && (transport == asoc->peer.active_path))
opt->pf->af->to_sk_saddr(&transport->saddr,
asoc->base.sk);
} else
transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}
/* Hold a reference to a transport. */
void sctp_transport_hold(struct sctp_transport *transport)
{
atomic_inc(&transport->refcnt);
}
/* Release a reference to a transport and clean up
* if there are no more references.
*/
void sctp_transport_put(struct sctp_transport *transport)
{
if (atomic_dec_and_test(&transport->refcnt))
sctp_transport_destroy(transport);
}
/* Update transport's RTO based on the newly calculated RTT. */
void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
{
/* Check for valid transport. */
SCTP_ASSERT(tp, "NULL transport", return);
/* We should not be doing any RTO updates unless rto_pending is set. */
SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
if (tp->rttvar || tp->srtt) {
/* 6.3.1 C3) When a new RTT measurement R' is made, set
* RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
* SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
*/
/* Note: The above algorithm has been rewritten to
* express rto_beta and rto_alpha as inverse powers
* of two.
* For example, assuming the default value of RTO.Alpha of
* 1/8, rto_alpha would be expressed as 3.
*/
tp->rttvar = tp->rttvar - (tp->rttvar >> sctp_rto_beta)
+ ((abs(tp->srtt - rtt)) >> sctp_rto_beta);
tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)
+ (rtt >> sctp_rto_alpha);
} else {
/* 6.3.1 C2) When the first RTT measurement R is made, set
* SRTT <- R, RTTVAR <- R/2.
*/
tp->srtt = rtt;
tp->rttvar = rtt >> 1;
}
/* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
* adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
*/
if (tp->rttvar == 0)
tp->rttvar = SCTP_CLOCK_GRANULARITY;
/* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
tp->rto = tp->srtt + (tp->rttvar << 2);
/* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
* seconds then it is rounded up to RTO.Min seconds.
*/
if (tp->rto < tp->asoc->rto_min)
tp->rto = tp->asoc->rto_min;
/* 6.3.1 C7) A maximum value may be placed on RTO provided it is
* at least RTO.max seconds.
*/
if (tp->rto > tp->asoc->rto_max)
tp->rto = tp->asoc->rto_max;
tp->rtt = rtt;
/* Reset rto_pending so that a new RTT measurement is started when a
* new data chunk is sent.
*/
tp->rto_pending = 0;
SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
"rttvar: %d, rto: %ld\n", __FUNCTION__,
tp, rtt, tp->srtt, tp->rttvar, tp->rto);
}
/* This routine updates the transport's cwnd and partial_bytes_acked
* parameters based on the bytes acked in the received SACK.
*/
void sctp_transport_raise_cwnd(struct sctp_transport *transport,
__u32 sack_ctsn, __u32 bytes_acked)
{
__u32 cwnd, ssthresh, flight_size, pba, pmtu;
cwnd = transport->cwnd;
flight_size = transport->flight_size;
/* The appropriate cwnd increase algorithm is performed if, and only
* if the cumulative TSN has advanced and the congestion window is
* being fully utilized.
*/
if ((transport->asoc->ctsn_ack_point >= sack_ctsn) ||
(flight_size < cwnd))
return;
ssthresh = transport->ssthresh;
pba = transport->partial_bytes_acked;
pmtu = transport->asoc->pathmtu;
if (cwnd <= ssthresh) {
/* RFC 2960 7.2.1, sctpimpguide-05 2.14.2 When cwnd is less
* than or equal to ssthresh an SCTP endpoint MUST use the
* slow start algorithm to increase cwnd only if the current
* congestion window is being fully utilized and an incoming
* SACK advances the Cumulative TSN Ack Point. Only when these
* two conditions are met can the cwnd be increased otherwise
* the cwnd MUST not be increased. If these conditions are met
* then cwnd MUST be increased by at most the lesser of
* 1) the total size of the previously outstanding DATA
* chunk(s) acknowledged, and 2) the destination's path MTU.
*/
if (bytes_acked > pmtu)
cwnd += pmtu;
else
cwnd += bytes_acked;
SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
"bytes_acked: %d, cwnd: %d, ssthresh: %d, "
"flight_size: %d, pba: %d\n",
__FUNCTION__,
transport, bytes_acked, cwnd,
ssthresh, flight_size, pba);
} else {
/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
* upon each SACK arrival that advances the Cumulative TSN Ack
* Point, increase partial_bytes_acked by the total number of
* bytes of all new chunks acknowledged in that SACK including
* chunks acknowledged by the new Cumulative TSN Ack and by
* Gap Ack Blocks.
*
* When partial_bytes_acked is equal to or greater than cwnd
* and before the arrival of the SACK the sender had cwnd or
* more bytes of data outstanding (i.e., before arrival of the
* SACK, flightsize was greater than or equal to cwnd),
* increase cwnd by MTU, and reset partial_bytes_acked to
* (partial_bytes_acked - cwnd).
*/
pba += bytes_acked;
if (pba >= cwnd) {
cwnd += pmtu;
pba = ((cwnd < pba) ? (pba - cwnd) : 0);
}
SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
"transport: %p, bytes_acked: %d, cwnd: %d, "
"ssthresh: %d, flight_size: %d, pba: %d\n",
__FUNCTION__,
transport, bytes_acked, cwnd,
ssthresh, flight_size, pba);
}
transport->cwnd = cwnd;
transport->partial_bytes_acked = pba;
}
/* This routine is used to lower the transport's cwnd when congestion is
* detected.
*/
void sctp_transport_lower_cwnd(struct sctp_transport *transport,
sctp_lower_cwnd_t reason)
{
switch (reason) {
case SCTP_LOWER_CWND_T3_RTX:
/* RFC 2960 Section 7.2.3, sctpimpguide
* When the T3-rtx timer expires on an address, SCTP should
* perform slow start by:
* ssthresh = max(cwnd/2, 4*MTU)
* cwnd = 1*MTU
* partial_bytes_acked = 0
*/
transport->ssthresh = max(transport->cwnd/2,
4*transport->asoc->pathmtu);
transport->cwnd = transport->asoc->pathmtu;
break;
case SCTP_LOWER_CWND_FAST_RTX:
/* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
* destination address(es) to which the missing DATA chunks
* were last sent, according to the formula described in
* Section 7.2.3.
*
* RFC 2960 7.2.3, sctpimpguide Upon detection of packet
* losses from SACK (see Section 7.2.4), An endpoint
* should do the following:
* ssthresh = max(cwnd/2, 4*MTU)
* cwnd = ssthresh
* partial_bytes_acked = 0
*/
transport->ssthresh = max(transport->cwnd/2,
4*transport->asoc->pathmtu);
transport->cwnd = transport->ssthresh;
break;
case SCTP_LOWER_CWND_ECNE:
/* RFC 2481 Section 6.1.2.
* If the sender receives an ECN-Echo ACK packet
* then the sender knows that congestion was encountered in the
* network on the path from the sender to the receiver. The
* indication of congestion should be treated just as a
* congestion loss in non-ECN Capable TCP. That is, the TCP
* source halves the congestion window "cwnd" and reduces the
* slow start threshold "ssthresh".
* A critical condition is that TCP does not react to
* congestion indications more than once every window of
* data (or more loosely more than once every round-trip time).
*/
if ((jiffies - transport->last_time_ecne_reduced) >
transport->rtt) {
transport->ssthresh = max(transport->cwnd/2,
4*transport->asoc->pathmtu);
transport->cwnd = transport->ssthresh;
transport->last_time_ecne_reduced = jiffies;
}
break;
case SCTP_LOWER_CWND_INACTIVE:
/* RFC 2960 Section 7.2.1, sctpimpguide
* When the endpoint does not transmit data on a given
* transport address, the cwnd of the transport address
* should be adjusted to max(cwnd/2, 4*MTU) per RTO.
* NOTE: Although the draft recommends that this check needs
* to be done every RTO interval, we do it every hearbeat
* interval.
*/
if ((jiffies - transport->last_time_used) > transport->rto)
transport->cwnd = max(transport->cwnd/2,
4*transport->asoc->pathmtu);
break;
}
transport->partial_bytes_acked = 0;
SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
"%d ssthresh: %d\n", __FUNCTION__,
transport, reason,
transport->cwnd, transport->ssthresh);
}
/* What is the next timeout value for this transport? */
unsigned long sctp_transport_timeout(struct sctp_transport *t)
{
unsigned long timeout;
timeout = t->rto + sctp_jitter(t->rto);
if (t->state != SCTP_UNCONFIRMED)
timeout += t->hbinterval;
timeout += jiffies;
return timeout;
}
/* Reset transport variables to their initial values */
void sctp_transport_reset(struct sctp_transport *t)
{
struct sctp_association *asoc = t->asoc;
/* RFC 2960 (bis), Section 5.2.4
* All the congestion control parameters (e.g., cwnd, ssthresh)
* related to this peer MUST be reset to their initial values
* (see Section 6.2.1)
*/
t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
t->ssthresh = asoc->peer.i.a_rwnd;
t->rto = asoc->rto_initial;
t->rtt = 0;
t->srtt = 0;
t->rttvar = 0;
/* Reset these additional varibles so that we have a clean
* slate.
*/
t->partial_bytes_acked = 0;
t->flight_size = 0;
t->error_count = 0;
t->rto_pending = 0;
/* Initialize the state information for SFR-CACC */
t->cacc.changeover_active = 0;
t->cacc.cycling_changeover = 0;
t->cacc.next_tsn_at_change = 0;
t->cacc.cacc_saw_newack = 0;
}