When performing a delete of an IPv6 route, BGP passes along a nexthop

to zebra. If the nexthop value is non-NULL, Zebra would attempt to find
a route that not only matches the prefix but also the nexthop i.e., treat
the delete as a specific ECMP path delete. However, the intent in BGP is
not a path delete but a delete of the entire prefix. If the deletion were
triggered by the nexthop for a prefix changing from NH1 to NH2 and NH2 is
not reachable, the delete would be issued to zebra for the prefix with the
nexthop as NH2 and zebra wouldn't delete the prefix as it still has NH1 as
its nexthop.

Fix by not sending any nexthop in IPv6 route delete. This is based on the
assumption (currently valid) that BGP does a route add/replace for any
path changes and issues a route delete only when it needs to delete the
entire route.

diff --git a/bgpd/bgp_zebra.c b/bgpd/bgp_zebra.c
index c91a25679dce728e2b7e0ed9fdeb9889d95045ca..37c65eefceb8d843e4cb11cd6928b9792efb00fb 100644 (file)
--- a/bgpd/bgp_zebra.c
+++ b/bgpd/bgp_zebra.c
@@ -1404,10 +1404,8 @@ bgp_zebra_withdraw (struct prefix *p, struct bgp_info *info, safi_t safi)
   if (p->family == AF_INET)
     {
       struct zapi_ipv4 api;
-      struct in_addr *nexthop;
 
       api.flags = flags;
-      nexthop = &info->attr->nexthop;
 
       api.type = ZEBRA_ROUTE_BGP;
       api.instance = 0;
@@ -1429,12 +1427,9 @@ bgp_zebra_withdraw (struct prefix *p, struct bgp_info *info, safi_t safi)
       if (bgp_debug_zebra(p))
        {
          char buf[2][INET_ADDRSTRLEN];
-         zlog_debug("Zebra send: IPv4 route delete %s/%d nexthop %s metric %u tag %d",
+         zlog_debug("Zebra send: IPv4 route delete %s/%d metric %u tag %d",
                     inet_ntop(AF_INET, &p->u.prefix4, buf[0], sizeof(buf[0])),
-                    p->prefixlen,
-                    inet_ntop(AF_INET, nexthop, buf[1], sizeof(buf[1])),
-                    api.metric,
-                    api.tag);
+                    p->prefixlen, api.metric, api.tag);
        }
 
       zapi_ipv4_route (ZEBRA_IPV4_ROUTE_DELETE, zclient, 
@@ -1445,44 +1440,18 @@ bgp_zebra_withdraw (struct prefix *p, struct bgp_info *info, safi_t safi)
   if (p->family == AF_INET6)
     {
       struct zapi_ipv6 api;
-      unsigned int ifindex;
-      struct in6_addr *nexthop;
       
       assert (info->attr->extra);
       
-      ifindex = 0;
-      nexthop = NULL;
-
-      /* Only global address nexthop exists. */
-      if (info->attr->extra->mp_nexthop_len == BGP_ATTR_NHLEN_IPV6_GLOBAL)
-       nexthop = &info->attr->extra->mp_nexthop_global;
-
-      /* If both global and link-local address present. */
-      if (info->attr->extra->mp_nexthop_len == BGP_ATTR_NHLEN_IPV6_GLOBAL_AND_LL)
-       {
-         nexthop = &info->attr->extra->mp_nexthop_local;
-         if (info->peer->nexthop.ifp)
-           ifindex = info->peer->nexthop.ifp->ifindex;
-       }
-
-      if (nexthop == NULL)
-       return;
-
-      if (IN6_IS_ADDR_LINKLOCAL (nexthop) && ! ifindex)
-       if (info->peer->conf_if || info->peer->ifname)
-         ifindex = if_nametoindex (info->peer->conf_if ? info->peer->conf_if : info->peer->ifname);
-
       api.flags = flags;
       api.type = ZEBRA_ROUTE_BGP;
       api.instance = 0;
       api.message = 0;
       api.safi = safi;
       SET_FLAG (api.message, ZAPI_MESSAGE_NEXTHOP);
-      api.nexthop_num = 1;
-      api.nexthop = &nexthop;
-      SET_FLAG (api.message, ZAPI_MESSAGE_IFINDEX);
-      api.ifindex_num = 1;
-      api.ifindex = &ifindex;
+      api.nexthop_num = 0;
+      api.nexthop = NULL;
+      api.ifindex_num = 0;
       SET_FLAG (api.message, ZAPI_MESSAGE_METRIC);
       api.metric = info->attr->med;
 
@@ -1495,12 +1464,9 @@ bgp_zebra_withdraw (struct prefix *p, struct bgp_info *info, safi_t safi)
       if (bgp_debug_zebra(p))
        {
          char buf[2][INET6_ADDRSTRLEN];
-         zlog_debug("Zebra send: IPv6 route delete %s/%d nexthop %s metric %u tag %d",
+         zlog_debug("Zebra send: IPv6 route delete %s/%d metric %u tag %d",
                     inet_ntop(AF_INET6, &p->u.prefix6, buf[0], sizeof(buf[0])),
-                    p->prefixlen,
-                    inet_ntop(AF_INET6, nexthop, buf[1], sizeof(buf[1])),
-                    api.metric,
-                     api.tag);
+                    p->prefixlen, api.metric, api.tag);
        }
 
       zapi_ipv6_route (ZEBRA_IPV6_ROUTE_DELETE, zclient,