litmus-rt.git - The LITMUS^RT kernel.

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Diffstat (limited to 'kernel/itimer.c')

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/* SCTP kernel 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 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. * * This SCTP 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. * * This SCTP 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, see * <http://www.gnu.org/licenses/>. * * Please send any bug reports or fixes you make to the * email address(es): * lksctp developers <linux-sctp@vger.kernel.org> * * 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> */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/slab.h> #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 net *net, 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); 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 * given destination transport address, set RTO to the protocol * parameter 'RTO.Initial'. */ peer->rto = msecs_to_jiffies(net->sctp.rto_initial); peer->last_time_heard = 0; peer->last_time_ecne_reduced = jiffies; peer->param_flags = SPP_HB_DISABLE | SPP_PMTUD_ENABLE | SPP_SACKDELAY_ENABLE; /* Initialize the default path max_retrans. */ peer->pathmaxrxt = net->sctp.max_retrans_path; peer->pf_retrans = net->sctp.pf_retrans; INIT_LIST_HEAD(&peer->transmitted); INIT_LIST_HEAD(&peer->send_ready); INIT_LIST_HEAD(&peer->transports); timer_setup(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event, 0); timer_setup(&peer->hb_timer, sctp_generate_heartbeat_event, 0); timer_setup(&peer->reconf_timer, sctp_generate_reconf_event, 0); timer_setup(&peer->proto_unreach_timer, sctp_generate_proto_unreach_event, 0); /* Initialize the 64-bit random nonce sent with heartbeat. */ get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce)); refcount_set(&peer->refcnt, 1); return peer; } /* Allocate and initialize a new transport. */ struct sctp_transport *sctp_transport_new(struct net *net, const union sctp_addr *addr, gfp_t gfp) { struct sctp_transport *transport; transport = kzalloc(sizeof(*transport), gfp); if (!transport) goto fail; if (!sctp_transport_init(net, transport, addr, gfp)) goto fail_init; 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) { /* 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 (del_timer(&transport->T3_rtx_timer)) sctp_transport_put(transport); if (del_timer(&transport->reconf_timer)) sctp_transport_put(transport); /* Delete the ICMP proto unreachable timer if it's active. */ if (del_timer(&transport->proto_unreach_timer)) sctp_association_put(transport->asoc); sctp_transport_put(transport); } static void sctp_transport_destroy_rcu(struct rcu_head *head) { struct sctp_transport *transport; transport = container_of(head, struct sctp_transport, rcu); dst_release(transport->dst); kfree(transport); SCTP_DBG_OBJCNT_DEC(transport); } /* Destroy the transport data structure. * Assumes there are no more users of this structure. */ static void sctp_transport_destroy(struct sctp_transport *transport) { if (unlikely(refcount_read(&transport->refcnt))) { WARN(1, "Attempt to destroy undead transport %p!\n", transport); return; } sctp_packet_free(&transport->packet); if (transport->asoc) sctp_association_put(transport->asoc); call_rcu(&transport->rcu, sctp_transport_destroy_rcu); } /* 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_t3_rtx(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); } void sctp_transport_reset_hb_timer(struct sctp_transport *transport) { unsigned long expires; /* When a data chunk is sent, reset the heartbeat interval. */ expires = jiffies + sctp_transport_timeout(transport); if (time_before(transport->hb_timer.expires, expires) && !mod_timer(&transport->hb_timer, expires + prandom_u32_max(transport->rto))) sctp_transport_hold(transport); } void sctp_transport_reset_reconf_timer(struct sctp_transport *transport) { if (!timer_pending(&transport->reconf_timer)) if (!mod_timer(&transport->reconf_timer, jiffies + transport->rto)) 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 sock *sk) { /* If we don't have a fresh route, look one up */ if (!transport->dst || transport->dst->obsolete) { sctp_transport_dst_release(transport); transport->af_specific->get_dst(transport, &transport->saddr, &transport->fl, sk); } if (transport->param_flags & SPP_PMTUD_DISABLE) { struct sctp_association *asoc = transport->asoc; if (!transport->pathmtu && asoc && asoc->pathmtu) transport->pathmtu = asoc->pathmtu; if (transport->pathmtu) return; } if (transport->dst) transport->pathmtu = sctp_dst_mtu(transport->dst); else transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT; } bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu) { struct dst_entry *dst = sctp_transport_dst_check(t); bool change = true; if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) { pr_warn_ratelimited("%s: Reported pmtu %d too low, using default minimum of %d\n", __func__, pmtu, SCTP_DEFAULT_MINSEGMENT); /* Use default minimum segment instead */ pmtu = SCTP_DEFAULT_MINSEGMENT; } pmtu = SCTP_TRUNC4(pmtu); if (dst) { dst->ops->update_pmtu(dst, t->asoc->base.sk, NULL, pmtu); dst = sctp_transport_dst_check(t); } if (!dst) { t->af_specific->get_dst(t, &t->saddr, &t->fl, t->asoc->base.sk); dst = t->dst; } if (dst) { /* Re-fetch, as under layers may have a higher minimum size */ pmtu = SCTP_TRUNC4(dst_mtu(dst)); change = t->pathmtu != pmtu; } t->pathmtu = pmtu; return change; } /* 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; sctp_transport_dst_release(transport); af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt)); if (saddr) memcpy(&transport->saddr, saddr, sizeof(union sctp_addr)); else af->get_saddr(opt, transport, &transport->fl); sctp_transport_pmtu(transport, sctp_opt2sk(opt)); /* Initialize sk->sk_rcv_saddr, if the transport is the * association's active path for getsockname(). */ if (transport->dst && asoc && (!asoc->peer.primary_path || transport == asoc->peer.active_path)) opt->pf->to_sk_saddr(&transport->saddr, asoc->base.sk); } /* Hold a reference to a transport. */ int sctp_transport_hold(struct sctp_transport *transport) { return refcount_inc_not_zero(&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 (refcount_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) { if (unlikely(!tp->rto_pending)) /* We should not be doing any RTO updates unless rto_pending is set. */ pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp); if (tp->rttvar || tp->srtt) { struct net *net = sock_net(tp->asoc->base.sk); /* 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 >> net->sctp.rto_beta) + (((__u32)abs((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta); tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha) + (rtt >> net->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; sctp_max_rto(tp->asoc, tp); 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; pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n", __func__, 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) { struct sctp_association *asoc = transport->asoc; __u32 cwnd, ssthresh, flight_size, pba, pmtu; cwnd = transport->cwnd; flight_size = transport->flight_size; /* See if we need to exit Fast Recovery first */ if (asoc->fast_recovery && TSN_lte(asoc->fast_recovery_exit, sack_ctsn)) asoc->fast_recovery = 0; ssthresh = transport->ssthresh; pba = transport->partial_bytes_acked; pmtu = transport->asoc->pathmtu; if (cwnd <= ssthresh) { /* RFC 4960 7.2.1 * o 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, an incoming SACK advances the Cumulative TSN * Ack Point, and the data sender is not in Fast Recovery. * Only when these three 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. This upper bound protects * against the ACK-Splitting attack outlined in [SAVAGE99]. */ if (asoc->fast_recovery) return; /* The appropriate cwnd increase algorithm is performed * if, and only if the congestion window is being fully * utilized. Note that RFC4960 Errata 3.22 removed the * other condition on ctsn moving. */ if (flight_size < cwnd) return; if (bytes_acked > pmtu) cwnd += pmtu; else cwnd += bytes_acked; pr_debug("%s: slow start: transport:%p, bytes_acked:%d, " "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n", __func__, transport, bytes_acked, cwnd, ssthresh, flight_size, pba); } else { /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh, * upon each SACK arrival, 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. (updated by RFC4960 Errata 3.22) * * When partial_bytes_acked is greater than cwnd and * before the arrival of the SACK the sender had less * bytes of data outstanding than cwnd (i.e., before * arrival of the SACK, flightsize was less than cwnd), * reset partial_bytes_acked to cwnd. (RFC 4960 Errata * 3.26) * * 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), partial_bytes_acked is reset * to (partial_bytes_acked - cwnd). Next, cwnd is * increased by MTU. (RFC 4960 Errata 3.12) */ pba += bytes_acked; if (pba > cwnd && flight_size < cwnd) pba = cwnd; if (pba >= cwnd && flight_size >= cwnd) { pba = pba - cwnd; cwnd += pmtu; } pr_debug("%s: congestion avoidance: transport:%p, " "bytes_acked:%d, cwnd:%d, ssthresh:%d, " "flight_size:%d, pba:%d\n", __func__, 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, enum sctp_lower_cwnd reason) { struct sctp_association *asoc = transport->asoc; 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*asoc->pathmtu); transport->cwnd = asoc->pathmtu; /* T3-rtx also clears fast recovery */ asoc->fast_recovery = 0; 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 */ if (asoc->fast_recovery) return; /* Mark Fast recovery */ asoc->fast_recovery = 1; asoc->fast_recovery_exit = asoc->next_tsn - 1; transport->ssthresh = max(transport->cwnd/2, 4*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 (time_after(jiffies, transport->last_time_ecne_reduced + transport->rtt)) { transport->ssthresh = max(transport->cwnd/2, 4*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. */ transport->cwnd = max(transport->cwnd/2, 4*asoc->pathmtu); /* RFC 4960 Errata 3.27.2: also adjust sshthresh */ transport->ssthresh = transport->cwnd; break; } transport->partial_bytes_acked = 0; pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n", __func__, transport, reason, transport->cwnd, transport->ssthresh); } /* Apply Max.Burst limit to the congestion window: * sctpimpguide-05 2.14.2 * D) When the time comes for the sender to * transmit new DATA chunks, the protocol parameter Max.Burst MUST * first be applied to limit how many new DATA chunks may be sent. * The limit is applied by adjusting cwnd as follows: * if ((flightsize+ Max.Burst * MTU) < cwnd) * cwnd = flightsize + Max.Burst * MTU */ void sctp_transport_burst_limited(struct sctp_transport *t) { struct sctp_association *asoc = t->asoc; u32 old_cwnd = t->cwnd; u32 max_burst_bytes; if (t->burst_limited || asoc->max_burst == 0) return; max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu); if (max_burst_bytes < old_cwnd) { t->cwnd = max_burst_bytes; t->burst_limited = old_cwnd; } } /* Restore the old cwnd congestion window, after the burst had it's * desired effect. */ void sctp_transport_burst_reset(struct sctp_transport *t) { if (t->burst_limited) { t->cwnd = t->burst_limited; t->burst_limited = 0; } } /* What is the next timeout value for this transport? */ unsigned long sctp_transport_timeout(struct sctp_transport *trans) { /* RTO + timer slack +/- 50% of RTO */ unsigned long timeout = trans->rto >> 1; if (trans->state != SCTP_UNCONFIRMED && trans->state != SCTP_PF) timeout += trans->hbinterval; return max_t(unsigned long, timeout, HZ / 5); } /* 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->burst_limited = 0; t->ssthresh = asoc->peer.i.a_rwnd; t->rto = asoc->rto_initial; sctp_max_rto(asoc, t); t->rtt = 0; t->srtt = 0; t->rttvar = 0; /* Reset these additional variables so that we have a clean slate. */ t->partial_bytes_acked = 0; t->flight_size = 0; t->error_count = 0; t->rto_pending = 0; t->hb_sent = 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; } /* Schedule retransmission on the given transport */ void sctp_transport_immediate_rtx(struct sctp_transport *t) { /* Stop pending T3_rtx_timer */ if (del_timer(&t->T3_rtx_timer)) sctp_transport_put(t); sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX); if (!timer_pending(&t->T3_rtx_timer)) { if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto)) sctp_transport_hold(t); } } /* Drop dst */ void sctp_transport_dst_release(struct sctp_transport *t) { dst_release(t->dst); t->dst = NULL; t->dst_pending_confirm = 0; } /* Schedule neighbour confirm */ void sctp_transport_dst_confirm(struct sctp_transport *t) { t->dst_pending_confirm = 1; }


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