I've seen several attempts recently made to do quick failover of sctp transports by reducing various retransmit timers and counters. While its possible to implement a faster failover on multihomed sctp associations, its not particularly robust, in that it can lead to unneeded retransmits, as well as false connection failures due to intermittent latency on a network. Instead, lets implement the new ietf quick failover draft found here: http://tools.ietf.org/html/draft-nishida-tsvwg-sctp-failover-05 This will let the sctp stack identify transports that have had a small number of errors, and avoid using them quickly until their reliability can be re-established. I've tested this out on two virt guests connected via multiple isolated virt networks and believe its in compliance with the above draft and works well. Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx> CC: Vlad Yasevich <vyasevich@xxxxxxxxx> CC: Sridhar Samudrala <sri@xxxxxxxxxx> CC: "David S. Miller" <davem@xxxxxxxxxxxxx> CC: linux-sctp@xxxxxxxxxxxxxxx --- Documentation/networking/ip-sysctl.txt | 14 +++++++++++++ include/net/sctp/constants.h | 1 + include/net/sctp/structs.h | 4 +++ include/net/sctp/user.h | 1 + net/sctp/associola.c | 33 +++++++++++++++++++++++++------ net/sctp/outqueue.c | 6 +++- net/sctp/sm_sideeffect.c | 33 ++++++++++++++++++++++++++++--- net/sctp/sysctl.c | 9 ++++++++ net/sctp/transport.c | 3 +- 9 files changed, 90 insertions(+), 14 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 47b6c79..c636f9c 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -1408,6 +1408,20 @@ path_max_retrans - INTEGER Default: 5 +pf_retrans - INTEGER + The number of retransmissions that will be attempted on a given path + before traffic is redirected to an alternate transport (should one + exist). Note this is distinct from path_max_retrans, as a path that + passes the pf_retrans threshold can still be used. Its only + deprioritized when a transmission path is selected by the stack. This + setting is primarily used to enable fast failover mechanisms without + having to reduce path_max_retrans to a very low value. See: + http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt + for details. Note also that a value of pf_retrans > path_max_retrans + disables this feature + + Default: 0 + rto_initial - INTEGER The initial round trip timeout value in milliseconds that will be used in calculating round trip times. This is the initial time interval diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h index 942b864..d053d2e 100644 --- a/include/net/sctp/constants.h +++ b/include/net/sctp/constants.h @@ -334,6 +334,7 @@ typedef enum { typedef enum { SCTP_TRANSPORT_UP, SCTP_TRANSPORT_DOWN, + SCTP_TRANSPORT_PF, } sctp_transport_cmd_t; /* These are the address scopes defined mainly for IPv4 addresses diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index e4652fe..22825abe 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h @@ -160,6 +160,7 @@ extern struct sctp_globals { int max_retrans_association; int max_retrans_path; int max_retrans_init; + int pf_retrans; /* * Policy for preforming sctp/socket accounting @@ -258,6 +259,7 @@ extern struct sctp_globals { #define sctp_sndbuf_policy (sctp_globals.sndbuf_policy) #define sctp_rcvbuf_policy (sctp_globals.rcvbuf_policy) #define sctp_max_retrans_path (sctp_globals.max_retrans_path) +#define sctp_pf_retrans (sctp_globals.pf_retrans) #define sctp_max_retrans_init (sctp_globals.max_retrans_init) #define sctp_sack_timeout (sctp_globals.sack_timeout) #define sctp_hb_interval (sctp_globals.hb_interval) @@ -1660,6 +1662,8 @@ struct sctp_association { */ int max_retrans; + int pf_retrans; + /* Maximum number of times the endpoint will retransmit INIT */ __u16 max_init_attempts; diff --git a/include/net/sctp/user.h b/include/net/sctp/user.h index 0842ef0..cece1bf 100644 --- a/include/net/sctp/user.h +++ b/include/net/sctp/user.h @@ -649,6 +649,7 @@ struct sctp_paddrinfo { */ enum sctp_spinfo_state { SCTP_INACTIVE, + SCTP_PF, SCTP_ACTIVE, SCTP_UNCONFIRMED, SCTP_UNKNOWN = 0xffff /* Value used for transport state unknown */ diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 5bc9ab1..f3ebc23 100644 --- a/net/sctp/associola.c +++ b/net/sctp/associola.c @@ -124,6 +124,8 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a * socket values. */ asoc->max_retrans = sp->assocparams.sasoc_asocmaxrxt; + asoc->pf_retrans = sctp_pf_retrans; + asoc->rto_initial = msecs_to_jiffies(sp->rtoinfo.srto_initial); asoc->rto_max = msecs_to_jiffies(sp->rtoinfo.srto_max); asoc->rto_min = msecs_to_jiffies(sp->rtoinfo.srto_min); @@ -840,6 +842,7 @@ void sctp_assoc_control_transport(struct sctp_association *asoc, struct sctp_ulpevent *event; struct sockaddr_storage addr; int spc_state = 0; + bool ulp_notify = true; /* Record the transition on the transport. */ switch (command) { @@ -853,6 +856,14 @@ void sctp_assoc_control_transport(struct sctp_association *asoc, spc_state = SCTP_ADDR_CONFIRMED; else spc_state = SCTP_ADDR_AVAILABLE; + /* Don't inform ULP about transition from PF to + * active state and set cwnd to 1, see SCTP + * Quick failover draft section 5.1, point 5 + */ + if (transport->state == SCTP_PF) { + ulp_notify = false; + transport->cwnd = 1; + } transport->state = SCTP_ACTIVE; break; @@ -871,6 +882,10 @@ void sctp_assoc_control_transport(struct sctp_association *asoc, spc_state = SCTP_ADDR_UNREACHABLE; break; + case SCTP_TRANSPORT_PF: + transport->state = SCTP_PF; + ulp_notify = false; + break; default: return; } @@ -878,12 +893,15 @@ void sctp_assoc_control_transport(struct sctp_association *asoc, /* Generate and send a SCTP_PEER_ADDR_CHANGE notification to the * user. */ - memset(&addr, 0, sizeof(struct sockaddr_storage)); - memcpy(&addr, &transport->ipaddr, transport->af_specific->sockaddr_len); - event = sctp_ulpevent_make_peer_addr_change(asoc, &addr, - 0, spc_state, error, GFP_ATOMIC); - if (event) - sctp_ulpq_tail_event(&asoc->ulpq, event); + if (ulp_notify) { + memset(&addr, 0, sizeof(struct sockaddr_storage)); + memcpy(&addr, &transport->ipaddr, + transport->af_specific->sockaddr_len); + event = sctp_ulpevent_make_peer_addr_change(asoc, &addr, + 0, spc_state, error, GFP_ATOMIC); + if (event) + sctp_ulpq_tail_event(&asoc->ulpq, event); + } /* Select new active and retran paths. */ @@ -899,7 +917,8 @@ void sctp_assoc_control_transport(struct sctp_association *asoc, transports) { if ((t->state == SCTP_INACTIVE) || - (t->state == SCTP_UNCONFIRMED)) + (t->state == SCTP_UNCONFIRMED) || + (t->state == SCTP_PF)) continue; if (!first || t->last_time_heard > first->last_time_heard) { second = first; diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c index a0fa19f..e7aa177c 100644 --- a/net/sctp/outqueue.c +++ b/net/sctp/outqueue.c @@ -792,7 +792,8 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout) if (!new_transport) new_transport = asoc->peer.active_path; } else if ((new_transport->state == SCTP_INACTIVE) || - (new_transport->state == SCTP_UNCONFIRMED)) { + (new_transport->state == SCTP_UNCONFIRMED) || + (new_transport->state == SCTP_PF)) { /* If the chunk is Heartbeat or Heartbeat Ack, * send it to chunk->transport, even if it's * inactive. @@ -987,7 +988,8 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout) new_transport = chunk->transport; if (!new_transport || ((new_transport->state == SCTP_INACTIVE) || - (new_transport->state == SCTP_UNCONFIRMED))) + (new_transport->state == SCTP_UNCONFIRMED) || + (new_transport->state == SCTP_PF))) new_transport = asoc->peer.active_path; if (new_transport->state == SCTP_UNCONFIRMED) continue; diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c index c96d1a8..285e26a 100644 --- a/net/sctp/sm_sideeffect.c +++ b/net/sctp/sm_sideeffect.c @@ -76,6 +76,8 @@ static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype, sctp_cmd_seq_t *commands, gfp_t gfp); +static void sctp_cmd_hb_timer_update(sctp_cmd_seq_t *cmds, + struct sctp_transport *t); /******************************************************************** * Helper functions ********************************************************************/ @@ -470,7 +472,8 @@ sctp_timer_event_t *sctp_timer_events[SCTP_NUM_TIMEOUT_TYPES] = { * notification SHOULD be sent to the upper layer. * */ -static void sctp_do_8_2_transport_strike(struct sctp_association *asoc, +static void sctp_do_8_2_transport_strike(sctp_cmd_seq_t *commands, + struct sctp_association *asoc, struct sctp_transport *transport, int is_hb) { @@ -495,6 +498,23 @@ static void sctp_do_8_2_transport_strike(struct sctp_association *asoc, transport->error_count++; } + /* If the transport error count is greater than the pf_retrans + * threshold, and less than pathmaxrtx, then mark this transport + * as Partially Failed, ee SCTP Quick Failover Draft, secon 5.1, + * point 1 + */ + if ((transport->state != SCTP_PF) && + (asoc->pf_retrans < transport->pathmaxrxt) && + (transport->error_count > asoc->pf_retrans)) { + + sctp_assoc_control_transport(asoc, transport, + SCTP_TRANSPORT_PF, + 0); + + /* Update the hb timer to resend a heartbeat every rto */ + sctp_cmd_hb_timer_update(commands, transport); + } + if (transport->state != SCTP_INACTIVE && (transport->error_count > transport->pathmaxrxt)) { SCTP_DEBUG_PRINTK_IPADDR("transport_strike:association %p", @@ -699,6 +719,10 @@ static void sctp_cmd_transport_on(sctp_cmd_seq_t *cmds, SCTP_HEARTBEAT_SUCCESS); } + if (t->state == SCTP_PF) + sctp_assoc_control_transport(asoc, t, SCTP_TRANSPORT_UP, + SCTP_HEARTBEAT_SUCCESS); + /* The receiver of the HEARTBEAT ACK should also perform an * RTT measurement for that destination transport address * using the time value carried in the HEARTBEAT ACK chunk. @@ -1565,8 +1589,8 @@ static int sctp_cmd_interpreter(sctp_event_t event_type, case SCTP_CMD_STRIKE: /* Mark one strike against a transport. */ - sctp_do_8_2_transport_strike(asoc, cmd->obj.transport, - 0); + sctp_do_8_2_transport_strike(commands, asoc, + cmd->obj.transport, 0); break; case SCTP_CMD_TRANSPORT_IDLE: @@ -1576,7 +1600,8 @@ static int sctp_cmd_interpreter(sctp_event_t event_type, case SCTP_CMD_TRANSPORT_HB_SENT: t = cmd->obj.transport; - sctp_do_8_2_transport_strike(asoc, t, 1); + sctp_do_8_2_transport_strike(commands, asoc, + t, 1); t->hb_sent = 1; break; diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c index e5fe639..2b2bfe9 100644 --- a/net/sctp/sysctl.c +++ b/net/sctp/sysctl.c @@ -141,6 +141,15 @@ static ctl_table sctp_table[] = { .extra2 = &int_max }, { + .procname = "pf_retrans", + .data = &sctp_pf_retrans, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &int_max + }, + { .procname = "max_init_retransmits", .data = &sctp_max_retrans_init, .maxlen = sizeof(int), diff --git a/net/sctp/transport.c b/net/sctp/transport.c index b026ba0..4639ba2 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -585,7 +585,8 @@ unsigned long sctp_transport_timeout(struct sctp_transport *t) { unsigned long timeout; timeout = t->rto + sctp_jitter(t->rto); - if (t->state != SCTP_UNCONFIRMED) + if ((t->state != SCTP_UNCONFIRMED) && + (t->state != SCTP_PF)) timeout += t->hbinterval; 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