BGP: Long-lived graceful restart enhancements

When use of LLGR is negotiated, handle hold timeout by LLGR instead of by
hard restart. Allow to configure whether BFD session down event should be
handled by GR/LLGR or by hard restart.

diff --git a/doc/bird.sgml b/doc/bird.sgml
index c66e8c72583bf0a7f3a5a35fda650dbb74075b7b..7cbb4de698d819cfc8a0ead26965797c688ecf52 100644 (file)
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1977,13 +1977,16 @@ using the following configuration parameters:
        immediately shut down. Note that this option cannot be used with
        multihop BGP. Default: disabled.
 
-       <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
-       <ref id="bfd" name="BFD"> section for details. Default: disabled.
+       failure. When a neighbor failure is detected, the BGP session is
+       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

diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index 0932051abdf6186acd7619a1669e83e4ea811fc0..369d78f579ece16e3f5e8d1b3ca6d137b9c8d72a 100644 (file)
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -704,6 +704,12 @@ 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->gr_ready && conn->peer_llgr_able)
+  {
+    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);
 }
@@ -1046,13 +1052,29 @@ bgp_bfd_notify(struct bfd_request *req)
   int ps = p->p.proto_state;
 
   if (req->down && ((ps == PS_START) || (ps == PS_UP)))
+  {
+    BGP_TRACE(D_EVENTS, "BFD session down");
+
+    /* Ignore if already in GR */
+    if (p->gr_active && (p->cf->bfd == BGP_BFD_GRACEFUL))
+      return;
+
+    if (p->conn && (p->conn->state == BS_ESTABLISHED) &&
+       p->gr_ready && (p->cf->bfd == BGP_BFD_GRACEFUL))
+    {
+      /* Trigger graceful restart */
+      bgp_handle_graceful_restart(p);
+      bgp_conn_enter_idle_state(p->conn);
+    }
+    else
     {
-      BGP_TRACE(D_EVENTS, "BFD session down");
+      /* Trigger session down */
       bgp_store_error(p, NULL, BE_MISC, BEM_BFD_DOWN);
       if (ps == PS_UP)
        bgp_update_startup_delay(p);
       bgp_stop(p, 0, NULL, 0);
     }
+  }
 }
 
 static void

diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 53194fb622d17ab600e19f36fa6ad13cb82198c0..7703fb6e96622c6d2e45f13117b2dd40c4e3fe90 100644 (file)
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -102,6 +102,8 @@ struct bgp_config {
 #define BGP_GRS_LLGR_1         2       /* Long-lived GR phase 1 (restart time) */
 #define BGP_GRS_LLGR_2         3       /* Long-lived GR phase 2 (stale time) */
 
+#define BGP_BFD_GRACEFUL       2       /* BFD down triggers graceful restart */
+
 
 struct bgp_conn {
   struct bgp_proto *bgp;

diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index 2ed1944df5dd423292c33beeac44031c6eaa95ad..95ceccb5f6f7d604873eb404dd2457cf5ca7ffb6 100644 (file)
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -172,6 +172,7 @@ bgp_proto:
  | 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); }
  ;
 
 CF_ADDTO(dynamic_attr, BGP_ORIGIN