BGP: Long-lived graceful restart

The patch implements long-lived graceful restart for BGP, namely
draft-uttaro-idr-bgp-persistence-03.

doc/bird.sgml

@@ -2220,13 +2220,16 @@ using the following configuration parameters:
 	immediately shut down. Note that this option cannot be used with
 	multihop BGP. Default: enabled for direct BGP, disabled otherwise.
 
-	<tag><label id="bgp-bfd">bfd <M>switch</M></tag>
+	<tag><label id="bgp-bfd">bfd <M>switch</M>|graceful</tag>
 	BGP could use BFD protocol as an advisory mechanism for neighbor
 	liveness and failure detection. If enabled, BIRD setups a BFD session
 	for the BGP neighbor and tracks its liveness by it. This has an
 	advantage of an order of magnitude lower detection times in case of
-	failure. Note that BFD protocol also has to be configured, see
+	failure. When a neighbor failure is detected, the BGP session is
-	<ref id="bfd" name="BFD"> section for details. Default: disabled.
+	restarted. Optionally, it can be configured (by <cf/graceful/ argument)
+	to trigger graceful restart instead of regular restart. Note that BFD
+	protocol also has to be configured, see <ref id="bfd" name="BFD">
+	section for details. Default: disabled.
 
 	<tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
 	Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
@@ -2348,6 +2351,25 @@ using the following configuration parameters:
 	re-establish after a restart before deleting stale routes. Default:
 	120 seconds.
 
+	<tag><label id="bgp-long-lived-graceful-restart">long lived graceful restart <m/switch/|aware</tag>
+	The long-lived graceful restart is an extension of the traditional
+	<ref id="bgp-graceful-restart" name="BGP graceful restart">, where stale
+	routes are kept even after the <ref id="bgp-graceful-restart-time"
+	name="restart time"> expires for additional long-lived stale time, but
+	they are marked with the LLGR_STALE community, depreferenced, and
+	withdrawn from routers not supporting LLGR. Like traditional BGP
+	graceful restart, it has three states: disabled, aware (receiving-only),
+	and enabled. Note that long-lived graceful restart requires at least
+	aware level of traditional BGP graceful restart. Default: aware, unless
+	graceful restart is disabled.
+
+	<tag><label id="bgp-long-lived-stale-time">long lived stale time <m/number/</tag>
+	The long-lived stale time is announced in the BGP long-lived graceful
+	restart capability and specifies how long the neighbor would keep stale
+	routes depreferenced during long-lived graceful restart until either the
+	session is re-stablished and synchronized or the stale time expires and
+	routes are removed. Default: 3600 seconds.
+
 	<tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
 	<rfc id="1997"> demands that BGP speaker should process well-known
 	communities like no-export (65535, 65281) or no-advertise (65535,
@@ -2607,6 +2629,19 @@ be used in explicit configuration.
 	configure restarting role per AFI/SAFI pair by this channel option.
 	The option is ignored if graceful restart is disabled by protocol-wide
 	option. Default: off in aware mode, on in full mode.
+
+	<tag><label id="bgp-long-lived-graceful-restart-c">long lived graceful restart <m/switch/</tag>
+	BGP long-lived graceful restart is configured mainly by protocol-wide
+	<ref id="bgp-long-lived-graceful-restart" name="options">, but the
+	restarting role can be set per AFI/SAFI pair by this channel option.
+	The option is ignored if long-lived graceful restart is disabled by
+	protocol-wide option. Default: off in aware mode, on in full mode.
+
+	<tag><label id="bgp-long-lived-stale-time-c">long lived stale time <m/number/</tag>
+	Like previous graceful restart channel options, this option allows to
+	set <ref id="bgp-long-lived-stale-time" name="long lived stale time">
+	per AFI/SAFI pair instead of per protocol. Default: set by protocol-wide
+	option.
 </descrip>
 
 <sect1>Attributes
@@ -2761,7 +2796,6 @@ interfaces to be defined for them to work with.
 	so the default time is set to a large value.
 
 	<tag><label id="device-iface">interface <m/pattern/ [, <m/.../]</tag>
-
 	By default, the Device protocol handles all interfaces without any
 	configuration. Interface definitions allow to specify optional
 	parameters for specific interfaces. See <ref id="proto-iface"

nest/protocol.h

@@ -229,6 +229,7 @@ struct proto {
   int (*rte_better)(struct rte *, struct rte *);
   int (*rte_same)(struct rte *, struct rte *);
   int (*rte_mergable)(struct rte *, struct rte *);
+  struct rte * (*rte_modify)(struct rte *, struct linpool *);
   void (*rte_insert)(struct network *, struct rte *);
   void (*rte_remove)(struct network *, struct rte *);
 

nest/route.h

@@ -231,6 +231,7 @@ typedef struct rte {
 #ifdef CONFIG_BGP
     struct {
       u8 suppressed;			/* Used for deterministic MED comparison */
+      s8 stale;				/* Route is LLGR_STALE, -1 if unknown */
     } bgp;
 #endif
 #ifdef CONFIG_BABEL
@@ -254,6 +255,7 @@ typedef struct rte {
 #define REF_FILTERED	2		/* Route is rejected by import filter */
 #define REF_STALE	4		/* Route is stale in a refresh cycle */
 #define REF_DISCARD	8		/* Route is scheduled for discard */
+#define REF_MODIFY	16		/* Route is scheduled for modify */
 
 /* Route is valid for propagation (may depend on other flags in the future), accepts NULL */
 static inline int rte_is_valid(rte *r) { return r && !(r->flags & REF_FILTERED); }
@@ -297,6 +299,7 @@ int rt_examine(rtable *t, net_addr *a, struct proto *p, struct filter *filter);
 rte *rt_export_merged(struct channel *c, net *net, rte **rt_free, linpool *pool, int silent);
 void rt_refresh_begin(rtable *t, struct channel *c);
 void rt_refresh_end(rtable *t, struct channel *c);
+void rt_modify_stale(rtable *t, struct channel *c);
 void rt_schedule_prune(rtable *t);
 void rte_dump(rte *);
 void rte_free(rte *);

nest/rt-table.c

@@ -1437,6 +1437,28 @@ rte_discard(rte *old)	/* Non-filtered route deletion, used during garbage collec
   rte_update_unlock();
 }
 
+/* Modify existing route by protocol hook, used for long-lived graceful restart */
+static inline void
+rte_modify(rte *old)
+{
+  rte_update_lock();
+
+  rte *new = old->sender->proto->rte_modify(old, rte_update_pool);
+  if (new != old)
+  {
+    if (new)
+    {
+      if (!rta_is_cached(new->attrs))
+	new->attrs = rta_lookup(new->attrs);
+      new->flags = (old->flags & ~REF_MODIFY) | REF_COW;
+    }
+
+    rte_recalculate(old->sender, old->net, new, old->attrs->src);
+  }
+
+  rte_update_unlock();
+}
+
 /* Check rtable for best route to given net whether it would be exported do p */
 int
 rt_examine(rtable *t, net_addr *a, struct proto *p, struct filter *filter)
@@ -1521,6 +1543,26 @@ rt_refresh_end(rtable *t, struct channel *c)
     rt_schedule_prune(t);
 }
 
+void
+rt_modify_stale(rtable *t, struct channel *c)
+{
+  int prune = 0;
+
+  FIB_WALK(&t->fib, net, n)
+    {
+      rte *e;
+      for (e = n->routes; e; e = e->next)
+	if ((e->sender == c) && (e->flags & REF_STALE) && !(e->flags & REF_FILTERED))
+	  {
+	    e->flags |= REF_MODIFY;
+	    prune = 1;
+	  }
+    }
+  FIB_WALK_END;
+
+  if (prune)
+    rt_schedule_prune(t);
+}
 
 /**
  * rte_dump - dump a route
@@ -1712,6 +1754,7 @@ again:
 
     rescan:
       for (e=n->routes; e; e=e->next)
+      {
 	if (e->sender->flush_active || (e->flags & REF_DISCARD))
 	  {
 	    if (limit <= 0)
@@ -1727,6 +1770,22 @@ again:
 	    goto rescan;
 	  }
 
+	if (e->flags & REF_MODIFY)
+	  {
+	    if (limit <= 0)
+	      {
+		FIB_ITERATE_PUT(fit);
+		ev_schedule(tab->rt_event);
+		return;
+	      }
+
+	    rte_modify(e);
+	    limit--;
+
+	    goto rescan;
+	  }
+      }
+
       if (!n->routes)		/* Orphaned FIB entry */
 	{
 	  FIB_ITERATE_PUT(fit);

proto/bgp/attrs.c

@@ -1413,6 +1413,10 @@ bgp_import_control(struct proto *P, rte **new, struct linpool *pool UNUSED)
     /* Do not export outside of AS (or confederation) */
     if (!p->is_interior && int_set_contains(d, BGP_COMM_NO_EXPORT))
       return -1;
+
+    /* Do not export LLGR_STALE routes to LLGR-ignorant peers */
+    if (!p->conn->remote_caps->llgr_aware && int_set_contains(d, BGP_COMM_LLGR_STALE))
+      return -1;
   }
 
   return 0;
@@ -1580,6 +1584,19 @@ rte_resolvable(rte *rt)
   return rt->attrs->dest == RTD_UNICAST;
 }
 
+static inline int
+rte_stale(rte *r)
+{
+  if (r->u.bgp.stale < 0)
+  {
+    /* If staleness is unknown, compute and cache it */
+    eattr *a = ea_find(r->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_COMMUNITY));
+    r->u.bgp.stale = a && int_set_contains(a->u.ptr, BGP_COMM_LLGR_STALE);
+  }
+
+  return r->u.bgp.stale;
+}
+
 int
 bgp_rte_better(rte *new, rte *old)
 {
@@ -1604,7 +1621,15 @@ bgp_rte_better(rte *new, rte *old)
   if (n < o)
     return 0;
 
-  /* Start with local preferences */
+  /* LLGR draft - depreference stale routes */
+  n = rte_stale(new);
+  o = rte_stale(old);
+  if (n > o)
+    return 0;
+  if (n < o)
+    return 1;
+
+ /* Start with local preferences */
   x = ea_find(new->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_LOCAL_PREF));
   y = ea_find(old->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_LOCAL_PREF));
   n = x ? x->u.data : new_bgp->cf->default_local_pref;
@@ -1725,6 +1750,10 @@ bgp_rte_mergable(rte *pri, rte *sec)
   if (!rte_resolvable(sec))
     return 0;
 
+  /* LLGR draft - depreference stale routes */
+  if (rte_stale(pri) != rte_stale(sec))
+    return 0;
+
   /* Start with local preferences */
   x = ea_find(pri->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_LOCAL_PREF));
   y = ea_find(sec->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_LOCAL_PREF));
@@ -1926,6 +1955,27 @@ bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best)
     return old_is_group_best;
 }
 
+struct rte *
+bgp_rte_modify_stale(struct rte *r, struct linpool *pool)
+{
+  eattr *a = ea_find(r->attrs->eattrs, EA_CODE(PROTOCOL_BGP, BA_COMMUNITY));
+  struct adata *ad = a ? a->u.ptr : NULL;
+  uint flags = a ? a->flags : BAF_PARTIAL;
+
+  if (ad && int_set_contains(ad, BGP_COMM_NO_LLGR))
+    return NULL;
+
+  if (ad && int_set_contains(ad, BGP_COMM_LLGR_STALE))
+    return r;
+
+  r = rte_cow_rta(r, pool);
+  bgp_set_attr_ptr(&(r->attrs->eattrs), pool, BA_COMMUNITY, flags,
+		   int_set_add(pool, ad, BGP_COMM_LLGR_STALE));
+  r->u.bgp.stale = 1;
+
+  return r;
+}
+
 
 /*
  * Reconstruct AS_PATH and AGGREGATOR according to RFC 6793 4.2.3
@@ -2011,6 +2061,9 @@ bgp_get_route_info(rte *e, byte *buf)
   if (e->u.bgp.suppressed)
     buf += bsprintf(buf, "-");
 
+  if (rte_stale(e))
+    buf += bsprintf(buf, "s");
+
   if (e->attrs->hostentry)
   {
     if (!rte_resolvable(e))

proto/bgp/bgp.c

@@ -513,8 +513,8 @@ bgp_conn_enter_established_state(struct bgp_conn *conn)
   p->route_refresh = peer->route_refresh;
   p->enhanced_refresh = local->enhanced_refresh && peer->enhanced_refresh;
 
-  /* Whether we may handle possible GR of peer (it has some AF GR-able) */
+  /* Whether we may handle possible GR/LLGR of peer (it has some AF GR-able) */
-  p->gr_ready = 0;	/* Updated later */
+  p->gr_ready = p->llgr_ready = 0;	/* Updated later */
 
   /* Whether peer is ready to handle our GR recovery */
   int peer_gr_ready = peer->gr_aware && !(peer->gr_flags & BGP_GRF_RESTART);
@@ -547,8 +547,15 @@ bgp_conn_enter_established_state(struct bgp_conn *conn)
     c->load_state = BFS_NONE;
 
     /* Channels where peer may do GR */
-    c->gr_ready = active && local->gr_aware && rem->gr_able;
+    uint gr_ready = active && local->gr_aware && rem->gr_able;
+    uint llgr_ready = active && local->llgr_aware && rem->llgr_able;
+
+    c->gr_ready = gr_ready || llgr_ready;
     p->gr_ready = p->gr_ready || c->gr_ready;
+    p->llgr_ready = p->llgr_ready || llgr_ready;
+
+    /* Remember last LLGR stale time */
+    c->stale_time = local->llgr_aware ? rem->llgr_time : 0;
 
     /* Channels not able to recover gracefully */
     if (p->p.gr_recovery && (!active || !peer_gr_ready))
@@ -558,8 +565,14 @@ bgp_conn_enter_established_state(struct bgp_conn *conn)
     if (p->p.gr_recovery && loc->gr_able && peer_gr_ready)
       c->c.gr_wait = 1;
 
-    /* Channels where peer is not able to recover gracefully */
+    /* Channels where regular graceful restart failed */
-    if (c->gr_active && ! (c->gr_ready && (rem->gr_af_flags & BGP_GRF_FORWARDING)))
+    if ((c->gr_active == BGP_GRS_ACTIVE) &&
+	!(active && rem->gr_able && (rem->gr_af_flags & BGP_GRF_FORWARDING)))
+      bgp_graceful_restart_done(c);
+
+    /* Channels where regular long-lived restart failed */
+    if ((c->gr_active == BGP_GRS_LLGR) &&
+	!(active && rem->llgr_able && (rem->gr_af_flags & BGP_LLGRF_FORWARDING)))
       bgp_graceful_restart_done(c);
 
     /* GR capability implies that neighbor will send End-of-RIB */
@@ -669,12 +682,25 @@ bgp_handle_graceful_restart(struct bgp_proto *p)
 
     if (c->gr_ready)
     {
-      if (c->gr_active)
-	rt_refresh_end(c->c.table, &c->c);
-
-      c->gr_active = 1;
       p->gr_active_num++;
-      rt_refresh_begin(c->c.table, &c->c);
+
+      switch (c->gr_active)
+      {
+      case BGP_GRS_NONE:
+	c->gr_active = BGP_GRS_ACTIVE;
+	rt_refresh_begin(c->c.table, &c->c);
+	break;
+
+      case BGP_GRS_ACTIVE:
+	rt_refresh_end(c->c.table, &c->c);
+	rt_refresh_begin(c->c.table, &c->c);
+	break;
+
+      case BGP_GRS_LLGR:
+	rt_refresh_begin(c->c.table, &c->c);
+	rt_modify_stale(c->c.table, &c->c);
+	break;
+      }
     }
     else
     {
@@ -695,7 +721,7 @@ bgp_handle_graceful_restart(struct bgp_proto *p)
   ASSERT(p->gr_active_num > 0);
 
   proto_notify_state(&p->p, PS_START);
-  bgp_start_timer(p->gr_timer, p->conn->remote_caps->gr_time);
+  tm_start(p->gr_timer, p->conn->remote_caps->gr_time S);
 }
 
 /**
@@ -720,6 +746,7 @@ bgp_graceful_restart_done(struct bgp_channel *c)
   if (!p->gr_active_num)
     BGP_TRACE(D_EVENTS, "Neighbor graceful restart done");
 
+  tm_stop(c->stale_timer);
   rt_refresh_end(c->c.table, &c->c);
 }
 
@@ -738,7 +765,46 @@ bgp_graceful_restart_timeout(timer *t)
   struct bgp_proto *p = t->data;
 
   BGP_TRACE(D_EVENTS, "Neighbor graceful restart timeout");
-  bgp_stop(p, 0, NULL, 0);
+
+  if (p->llgr_ready)
+  {
+    struct bgp_channel *c;
+    WALK_LIST(c, p->p.channels)
+    {
+      /* Channel is not in GR and is already flushed */
+      if (!c->gr_active)
+	continue;
+
+      /* Channel is already in LLGR from past restart */
+      if (c->gr_active == BGP_GRS_LLGR)
+	continue;
+
+      /* Channel is in GR, but does not support LLGR -> stop GR */
+      if (!c->stale_time)
+      {
+	bgp_graceful_restart_done(c);
+	continue;
+      }
+
+      /* Channel is in GR, and supports LLGR -> start LLGR */
+      c->gr_active = BGP_GRS_LLGR;
+      tm_start(c->stale_timer, c->stale_time S);
+      rt_modify_stale(c->c.table, &c->c);
+    }
+  }
+  else
+    bgp_stop(p, 0, NULL, 0);
+}
+
+static void
+bgp_long_lived_stale_timeout(timer *t)
+{
+  struct bgp_channel *c = t->data;
+  struct bgp_proto *p = (void *) c->c.proto;
+
+  BGP_TRACE(D_EVENTS, "Long-lived stale timeout");
+
+  bgp_graceful_restart_done(c);
 }
 
 
@@ -873,6 +939,12 @@ bgp_hold_timeout(timer *t)
 
   if (sk_rx_ready(conn->sk) > 0)
     bgp_start_timer(conn->hold_timer, 10);
+  else if ((conn->state == BS_ESTABLISHED) && p->llgr_ready)
+  {
+    BGP_TRACE(D_EVENTS, "Hold timer expired");
+    bgp_handle_graceful_restart(p);
+    bgp_conn_enter_idle_state(conn);
+  }
   else
     bgp_error(conn, 4, 0, NULL, 0);
 }
@@ -1172,9 +1244,26 @@ bgp_bfd_notify(struct bfd_request *req)
   {
     BGP_TRACE(D_EVENTS, "BFD session down");
     bgp_store_error(p, NULL, BE_MISC, BEM_BFD_DOWN);
-    if (ps == PS_UP)
+
-      bgp_update_startup_delay(p);
+    if (p->cf->bfd == BGP_BFD_GRACEFUL)
-    bgp_stop(p, 0, NULL, 0);
+    {
+      /* Trigger graceful restart */
+      if (p->conn && (p->conn->state == BS_ESTABLISHED) && p->gr_ready)
+	bgp_handle_graceful_restart(p);
+
+      if (p->incoming_conn.state > BS_IDLE)
+	bgp_conn_enter_idle_state(&p->incoming_conn);
+
+      if (p->outgoing_conn.state > BS_IDLE)
+	bgp_conn_enter_idle_state(&p->outgoing_conn);
+    }
+    else
+    {
+      /* Trigger session down */
+      if (ps == PS_UP)
+	bgp_update_startup_delay(p);
+      bgp_stop(p, 0, NULL, 0);
+    }
   }
 }
 
@@ -1447,6 +1536,7 @@ bgp_init(struct proto_config *CF)
   P->rte_better = bgp_rte_better;
   P->rte_mergable = bgp_rte_mergable;
   P->rte_recalculate = cf->deterministic_med ? bgp_rte_recalculate : NULL;
+  P->rte_modify = bgp_rte_modify_stale;
 
   p->cf = cf;
   p->local_as = cf->local_as;
@@ -1503,6 +1593,8 @@ bgp_channel_start(struct channel *C)
   bgp_init_bucket_table(c);
   bgp_init_prefix_table(c);
 
+  c->stale_timer = tm_new_init(c->pool, bgp_long_lived_stale_timeout, c, 0, 0);
+
   c->next_hop_addr = c->cf->next_hop_addr;
   c->link_addr = IPA_NONE;
   c->packets_to_send = 0;
@@ -1634,6 +1726,10 @@ bgp_postconfig(struct proto_config *CF)
   if (cf->multihop < 0)
     cf->multihop = internal ? 64 : 0;
 
+  /* LLGR mode default based on GR mode */
+  if (cf->llgr_mode < 0)
+    cf->llgr_mode = cf->gr_mode ? BGP_LLGR_AWARE : 0;
+
   /* Link check for single-hop BGP by default */
   if (cf->check_link < 0)
     cf->check_link = !cf->multihop;
@@ -1676,6 +1772,9 @@ bgp_postconfig(struct proto_config *CF)
   if (cf->multihop && cf->bfd && ipa_zero(cf->local_ip))
     cf_error("Multihop BGP with BFD requires specified local address");
 
+  if (!cf->gr_mode && cf->llgr_mode)
+    cf_error("Long-lived graceful restart requires basic graceful restart");
+
 
   struct bgp_channel_config *cc;
   WALK_LIST(cc, CF->channels)
@@ -1706,10 +1805,16 @@ bgp_postconfig(struct proto_config *CF)
     if (!cc->gw_mode)
       cc->gw_mode = cf->multihop ? GW_RECURSIVE : GW_DIRECT;
 
-    /* Default based on proto config */
+    /* Defaults based on proto config */
     if (cc->gr_able == 0xff)
       cc->gr_able = (cf->gr_mode == BGP_GR_ABLE);
 
+    if (cc->llgr_able == 0xff)
+      cc->llgr_able = (cf->llgr_mode == BGP_LLGR_ABLE);
+
+    if (cc->llgr_time == ~0U)
+      cc->llgr_time = cf->llgr_time;
+
     /* Default values of IGP tables */
     if ((cc->gw_mode == GW_RECURSIVE) && !cc->desc->no_igp)
     {
@@ -1885,6 +1990,7 @@ static char *bgp_state_names[] = { "Idle", "Connect", "Active", "OpenSent", "Ope
 static char *bgp_err_classes[] = { "", "Error: ", "Socket: ", "Received: ", "BGP Error: ", "Automatic shutdown: ", ""};
 static char *bgp_misc_errors[] = { "", "Neighbor lost", "Invalid next hop", "Kernel MD5 auth failed", "No listening socket", "Link down", "BFD session down", "Graceful restart"};
 static char *bgp_auto_errors[] = { "", "Route limit exceeded"};
+static char *bgp_gr_states[] = { "None", "Regular", "Long-lived"};
 
 static const char *
 bgp_last_errmsg(struct bgp_proto *p)
@@ -1963,6 +2069,7 @@ bgp_show_capabilities(struct bgp_proto *p UNUSED, struct bgp_caps *caps)
   uint any_gr_able = 0;
   uint any_add_path = 0;
   uint any_ext_next_hop = 0;
+  uint any_llgr_able = 0;
   u32 *afl1 = alloca(caps->af_count * sizeof(u32));
   u32 *afl2 = alloca(caps->af_count * sizeof(u32));
   uint afn1, afn2;
@@ -1973,6 +2080,7 @@ bgp_show_capabilities(struct bgp_proto *p UNUSED, struct bgp_caps *caps)
     any_gr_able |= ac->gr_able;
     any_add_path |= ac->add_path;
     any_ext_next_hop |= ac->ext_next_hop;
+    any_llgr_able |= ac->llgr_able;
   }
 
   if (any_mp_bgp)
@@ -2052,6 +2160,32 @@ bgp_show_capabilities(struct bgp_proto *p UNUSED, struct bgp_caps *caps)
 
   if (caps->enhanced_refresh)
     cli_msg(-1006, "      Enhanced refresh");
+
+  if (caps->llgr_aware)
+    cli_msg(-1006, "      Long-lived graceful restart");
+
+  if (any_llgr_able)
+  {
+    u32 stale_time = 0;
+
+    afn1 = afn2 = 0;
+    WALK_AF_CAPS(caps, ac)
+    {
+      stale_time = MAX(stale_time, ac->llgr_time);
+
+      if (ac->llgr_able && ac->llgr_time)
+	afl1[afn1++] = ac->afi;
+
+      if (ac->llgr_flags & BGP_GRF_FORWARDING)
+	afl2[afn2++] = ac->afi;
+    }
+
+    /* Continues from llgr_aware */
+    cli_msg(-1006, "        LL stale time: %u", stale_time);
+
+    bgp_show_afis(-1006, "        AF supported:", afl1, afn1);
+    bgp_show_afis(-1006, "        AF preserved:", afl2, afn2);
+  }
 }
 
 static void
@@ -2118,6 +2252,12 @@ bgp_show_proto_info(struct proto *P)
     {
       channel_show_info(&c->c);
 
+      if (p->gr_active_num)
+	cli_msg(-1006, "    Neighbor GR:    %s", bgp_gr_states[c->gr_active]);
+
+      if (tm_active(c->stale_timer))
+	cli_msg(-1006, "    LL stale timer: %t/-", tm_remains(c->stale_timer));
+
       if (c->c.channel_state == CS_UP)
       {
 	if (ipa_zero(c->link_addr))

proto/bgp/bgp.h

@@ -107,9 +107,11 @@ struct bgp_config {
   int allow_local_as;			/* Allow that number of local ASNs in incoming AS_PATHs */
   int allow_local_pref;			/* Allow LOCAL_PREF in EBGP sessions */
   int gr_mode;				/* Graceful restart mode (BGP_GR_*) */
+  int llgr_mode;			/* Long-lived graceful restart mode (BGP_LLGR_*) */
   int setkey;				/* Set MD5 password to system SA/SP database */
   /* Times below are in seconds */
   unsigned gr_time;			/* Graceful restart timeout */
+  unsigned llgr_time;			/* Long-lived graceful restart stale time */
   unsigned connect_delay_time;		/* Minimum delay between connect attempts */
   unsigned connect_retry_time;		/* Timeout for connect attempts */
   unsigned hold_time, initial_hold_time;
@@ -138,6 +140,8 @@ struct bgp_channel_config {
   u8 gw_mode;				/* How we compute route gateway from next_hop attr, see GW_* */
   u8 secondary;				/* Accept also non-best routes (i.e. RA_ACCEPTED) */
   u8 gr_able;				/* Allow full graceful restart for the channel */
+  u8 llgr_able;				/* Allow full long-lived GR for the channel */
+  uint llgr_time;			/* Long-lived graceful restart stale time */
   u8 ext_next_hop;			/* Allow both IPv4 and IPv6 next hops */
   u8 add_path;				/* Use ADD-PATH extension [RFC 7911] */
 
@@ -166,12 +170,26 @@ struct bgp_channel_config {
 /* For GR capability per-AF flags */
 #define BGP_GRF_FORWARDING 0x80
 
+#define BGP_LLGR_ABLE		1
+#define BGP_LLGR_AWARE		2
+
+#define BGP_LLGRF_FORWARDING 0x80
+
+#define BGP_GRS_NONE		0	/* No GR  */
+#define BGP_GRS_ACTIVE		1	/* Graceful restart per RFC 4724 */
+#define BGP_GRS_LLGR		2	/* Long-lived GR phase (stale timer active) */
+
+#define BGP_BFD_GRACEFUL	2	/* BFD down triggers graceful restart */
+
 
 struct bgp_af_caps {
   u32 afi;
   u8 ready;				/* Multiprotocol capability, RFC 4760 */
   u8 gr_able;				/* Graceful restart support, RFC 4724 */
   u8 gr_af_flags;			/* Graceful restart per-AF flags */
+  u8 llgr_able;				/* Long-lived GR, RFC draft */
+  u32 llgr_time;			/* Long-lived GR stale time */
+  u8 llgr_flags;			/* Long-lived GR per-AF flags */
   u8 ext_next_hop;			/* Extended IPv6 next hop,   RFC 5549 */
   u8 add_path;				/* Multiple paths support,   RFC 7911 */
 };
@@ -188,6 +206,8 @@ struct bgp_caps {
   u8 gr_flags;				/* Graceful restart flags */
   u16 gr_time;				/* Graceful restart time in seconds */
 
+  u8 llgr_aware;			/* Long-lived GR capability, RFC draft */
+
   u16 af_count;				/* Number of af_data items */
 
   struct bgp_af_caps af_data[0];	/* Per-AF capability data */
@@ -243,6 +263,7 @@ struct bgp_proto {
   u8 route_refresh;			/* Route refresh allowed to send [RFC 2918] */
   u8 enhanced_refresh;			/* Enhanced refresh is negotiated [RFC 7313] */
   u8 gr_ready;				/* Neighbor could do graceful restart */
+  u8 llgr_ready;			/* Neighbor could do Long-lived GR, implies gr_ready */
   u8 gr_active_num;			/* Neighbor is doing GR, number of active channels */
   u8 channel_count;			/* Number of active channels */
   u32 *afi_map;				/* Map channel index -> AFI */
@@ -291,11 +312,14 @@ struct bgp_channel {
 
   u32 packets_to_send;			/* Bitmap of packet types to be sent */
 
-  u8 gr_ready;				/* Neighbor could do GR on this AF */
-  u8 gr_active;				/* Neighbor is doing GR and keeping fwd state */
-
   u8 ext_next_hop;			/* Session allows both IPv4 and IPv6 next hops */
 
+  u8 gr_ready;				/* Neighbor could do GR on this AF */
+  u8 gr_active;				/* Neighbor is doing GR (BGP_GRS_*) */
+
+  timer *stale_timer;			/* Long-lived stale timer for LLGR */
+  u32 stale_time;			/* Stored LLGR stale time from last session */
+
   u8 add_path_rx;			/* Session expects receive of ADD-PATH extended NLRI */
   u8 add_path_tx;			/* Session expects transmit of ADD-PATH extended NLRI */
 
@@ -505,6 +529,7 @@ void bgp_free_prefix(struct bgp_channel *c, struct bgp_prefix *bp);
 int bgp_rte_better(struct rte *, struct rte *);
 int bgp_rte_mergable(rte *pri, rte *sec);
 int bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best);
+struct rte *bgp_rte_modify_stale(struct rte *r, struct linpool *pool);
 void bgp_rt_notify(struct proto *P, struct channel *C, net *n, rte *new, rte *old);
 int bgp_import_control(struct proto *, struct rte **, struct linpool *);
 int bgp_get_attr(struct eattr *e, byte *buf, int buflen);
@@ -645,6 +670,9 @@ void bgp_update_next_hop(struct bgp_export_state *s, eattr *a, ea_list **to);
 #define BGP_COMM_NO_ADVERTISE		0xffffff02	/* Don't export at all */
 #define BGP_COMM_NO_EXPORT_SUBCONFED	0xffffff03	/* NO_EXPORT even in local confederation */
 
+#define BGP_COMM_LLGR_STALE		0xffff0006	/* Route is stale according to LLGR */
+#define BGP_COMM_NO_LLGR		0xffff0007	/* Do not treat the route according to LLGR */
+
 /* Origins */
 
 #define ORIGIN_IGP		0

proto/bgp/config.Y

@@ -28,7 +28,8 @@ CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, KEEPALIVE,
 	BGP_CLUSTER_LIST, IGP, TABLE, GATEWAY, DIRECT, RECURSIVE, MED, TTL,
 	SECURITY, DETERMINISTIC, SECONDARY, ALLOW, BFD, ADD, PATHS, RX, TX,
 	GRACEFUL, RESTART, AWARE, CHECK, LINK, PORT, EXTENDED, MESSAGES, SETKEY,
-	STRICT, BIND, CONFEDERATION, MEMBER, MULTICAST, FLOW4, FLOW6)
+	STRICT, BIND, CONFEDERATION, MEMBER, MULTICAST, FLOW4, FLOW6, LONG,
+	LIVED, STALE)
 
 %type <i32> bgp_afi
 
@@ -63,6 +64,8 @@ bgp_proto_start: proto_start BGP {
      BGP_CFG->default_local_pref = 100;
      BGP_CFG->gr_mode = BGP_GR_AWARE;
      BGP_CFG->gr_time = 120;
+     BGP_CFG->llgr_mode = -1;
+     BGP_CFG->llgr_time = 3600;
      BGP_CFG->setkey = 1;
      BGP_CFG->check_link = -1;
    }
@@ -161,9 +164,13 @@ bgp_proto:
  | bgp_proto GRACEFUL RESTART bool ';' { BGP_CFG->gr_mode = $4; }
  | bgp_proto GRACEFUL RESTART AWARE ';' { BGP_CFG->gr_mode = BGP_GR_AWARE; }
  | bgp_proto GRACEFUL RESTART TIME expr ';' { BGP_CFG->gr_time = $5; }
+ | bgp_proto LONG LIVED GRACEFUL RESTART bool ';' { BGP_CFG->llgr_mode = $6; }
+ | bgp_proto LONG LIVED GRACEFUL RESTART AWARE ';' { BGP_CFG->llgr_mode = BGP_LLGR_AWARE; }
+ | bgp_proto LONG LIVED STALE TIME expr ';' { BGP_CFG->llgr_time = $6; }
  | bgp_proto TTL SECURITY bool ';' { BGP_CFG->ttl_security = $4; }
  | bgp_proto CHECK LINK bool ';' { BGP_CFG->check_link = $4; }
  | bgp_proto BFD bool ';' { BGP_CFG->bfd = $3; cf_check_bfd($3); }
+ | bgp_proto BFD GRACEFUL ';' { BGP_CFG->bfd = BGP_BFD_GRACEFUL; cf_check_bfd(1); }
  ;
 
 bgp_afi:
@@ -199,6 +206,8 @@ bgp_channel_start: bgp_afi
     BGP_CC->afi = $1;
     BGP_CC->desc = desc;
     BGP_CC->gr_able = 0xff;	/* undefined */
+    BGP_CC->llgr_able = 0xff;	/* undefined */
+    BGP_CC->llgr_time = ~0U;	/* undefined */
   }
 };
 
@@ -214,6 +223,8 @@ bgp_channel_item:
  | GATEWAY RECURSIVE { BGP_CC->gw_mode = GW_RECURSIVE; }
  | SECONDARY bool { BGP_CC->secondary = $2; }
  | GRACEFUL RESTART bool { BGP_CC->gr_able = $3; }
+ | LONG LIVED GRACEFUL RESTART bool { BGP_CC->llgr_able = $5; }
+ | LONG LIVED STALE TIME expr { BGP_CC->llgr_time = $5; }
  | EXTENDED NEXT HOP bool { BGP_CC->ext_next_hop = $4; }
  | ADD PATHS RX { BGP_CC->add_path = BGP_ADD_PATH_RX; }
  | ADD PATHS TX { BGP_CC->add_path = BGP_ADD_PATH_TX; }

proto/bgp/packets.c

@@ -260,6 +260,9 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
     caps->gr_flags = p->p.gr_recovery ? BGP_GRF_RESTART : 0;
   }
 
+  if (p->cf->llgr_mode)
+    caps->llgr_aware = 1;
+
   /* Allocate and fill per-AF fields */
   WALK_LIST(c, p->p.channels)
   {
@@ -280,6 +283,15 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
       if (p->p.gr_recovery)
 	ac->gr_af_flags |= BGP_GRF_FORWARDING;
     }
+
+    if (c->cf->llgr_able)
+    {
+      ac->llgr_able = 1;
+      ac->llgr_time = c->cf->llgr_time;
+
+      if (p->p.gr_recovery)
+	ac->llgr_flags |= BGP_LLGRF_FORWARDING;
+    }
   }
 
   /* Sort capability fields by AFI/SAFI */
@@ -289,9 +301,9 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
   /* Create capability list in buffer */
 
   /*
-   * Note that max length is ~ 20+14*af_count. With max 12 channels that is
+   * Note that max length is ~ 22+21*af_count. With max 12 channels that is
-   * 188. Option limit is 253 and buffer size is 4096, so we cannot overflow
+   * 274. Option limit is 253 and buffer size is 4096, so we cannot overflow
-   * unless we add new capabilities or more AFs.
+   * unless we add new capabilities or more AFs. XXXXX
    */
 
   WALK_AF_CAPS(caps, ac)
@@ -384,6 +396,24 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
     *buf++ = 0;			/* Capability data length */
   }
 
+  if (caps->llgr_aware)
+  {
+    *buf++ = 71;		/* Capability 71: Support for long-lived graceful restart */
+    *buf++ = 0;			/* Capability data length, will be fixed later */
+    data = buf;
+
+    WALK_AF_CAPS(caps, ac)
+      if (ac->llgr_able)
+      {
+	put_af3(buf, ac->afi);
+	buf[3] = ac->llgr_flags;
+	put_u24(buf+4, ac->llgr_time);
+	buf += 7;
+      }
+
+    data[-1] = buf - data;
+  }
+
   return buf;
 }
 
@@ -508,11 +538,49 @@ bgp_read_capabilities(struct bgp_conn *conn, struct bgp_caps *caps, byte *pos, i
       caps->enhanced_refresh = 1;
       break;
 
+    case 71: /* Long lived graceful restart capability, RFC draft */
+      if (cl % 7)
+	goto err;
+
+      /* Presumably, only the last instance is valid */
+      WALK_AF_CAPS(caps, ac)
+      {
+	ac->llgr_able = 0;
+	ac->llgr_flags = 0;
+	ac->llgr_time = 0;
+      }
+
+      caps->llgr_aware = 1;
+
+      for (i = 0; i < cl; i += 7)
+      {
+	af = get_af3(pos+2+i);
+	ac = bgp_get_af_caps(caps, af);
+	ac->llgr_able = 1;
+	ac->llgr_flags = pos[2+i+3];
+	ac->llgr_time = get_u24(pos + 2+i+4);
+      }
+      break;
+
       /* We can safely ignore all other capabilities */
     }
 
     ADVANCE(pos, len, 2 + cl);
   }
+
+  /* The LLGR capability must be advertised together with the GR capability,
+     otherwise it must be disregarded */
+  if (!caps->gr_aware && caps->llgr_aware)
+  {
+    caps->llgr_aware = 0;
+    WALK_AF_CAPS(caps, ac)
+    {
+      ac->llgr_able = 0;
+      ac->llgr_flags = 0;
+      ac->llgr_time = 0;
+    }
+  }
+
   return;
 
 err:
@@ -1131,6 +1199,7 @@ bgp_rte_update(struct bgp_parse_state *s, net_addr *n, u32 path_id, rta *a0)
 
   e->pflags = 0;
   e->u.bgp.suppressed = 0;
+  e->u.bgp.stale = -1;
   rte_update2(&s->channel->c, n, e, s->last_src);
 }
 

proto/pipe/pipe.c

@@ -78,6 +78,12 @@ pipe_rt_notify(struct proto *P, struct channel *src_ch, net *n, rte *new, rte *o
       e->pref = new->pref;
       e->pflags = new->pflags;
 
+#ifdef CONFIG_BGP
+      /* Hack to cleanup cached value */
+      if (e->attrs->src->proto->proto == &proto_bgp)
+	e->u.bgp.stale = -1;
+#endif
+
       src = a->src;
     }
   else