zebra: Modify nexthop checks to report inactive a bit more

Debugging inactive nexthops in zebra can be quite difficult
and non-obvious what has gone wrong.  Add detailed rib
debugs for the cases where we decide that a nexthop is
inactive so that we can more easily debug a reason
for the failure.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>

diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
index 49d2f26943a05cb0c4eaf21793dd0a68616fce2d..0739db10271209d80f3609d48d5dd0d567dd8a16 100644 (file)
--- a/zebra/zebra_rib.c
+++ b/zebra/zebra_rib.c
@@ -428,8 +428,12 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
        /* Skip nexthops that have been filtered out due to route-map */
        /* The nexthops are specific to this route and so the same */
        /* nexthop for a different route may not have this flag set */
-       if (CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_FILTERED))
+       if (CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_FILTERED)) {
+               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                       zlog_debug("\t%s: Nexthop Filtered",
+                                  __PRETTY_FUNCTION__);
                return 0;
+       }
 
        /*
         * Check to see if we should trust the passed in information
@@ -441,10 +445,21 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
                if (ifp && connected_is_unnumbered(ifp)) {
                        if (if_is_operative(ifp))
                                return 1;
-                       else
+                       else {
+                               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                                       zlog_debug(
+                                               "\t%s: Onlink and interface %s is not operative",
+                                               __PRETTY_FUNCTION__, ifp->name);
                                return 0;
-               } else
+                       }
+               } else {
+                       if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                               zlog_debug(
+                                       "\t%s: Interface %s is not unnumbered",
+                                       __PRETTY_FUNCTION__,
+                                       ifp ? ifp->name : "Unknown");
                        return 0;
+               }
        }
 
        /* Make lookup prefix. */
@@ -466,8 +481,12 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
        }
        /* Lookup table.  */
        table = zebra_vrf_table(afi, SAFI_UNICAST, nexthop->vrf_id);
-       if (!table)
+       if (!table) {
+               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                       zlog_debug("\t%s: Table not found",
+                                  __PRETTY_FUNCTION__);
                return 0;
+       }
 
        rn = route_node_match(table, (struct prefix *)&p);
        while (rn) {
@@ -480,15 +499,25 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
                 */
                if (top && rn == top)
                        if (((afi == AFI_IP) && (rn->p.prefixlen != 32))
-                           || ((afi == AFI_IP6) && (rn->p.prefixlen != 128)))
+                           || ((afi == AFI_IP6) && (rn->p.prefixlen != 128))) {
+                               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                                       zlog_debug(
+                                               "\t%s: Matched against ourself and prefix length is not max bit length",
+                                               __PRETTY_FUNCTION__);
                                return 0;
+                       }
 
                /* Pick up selected route. */
                /* However, do not resolve over default route unless explicitly
                 * allowed. */
                if (is_default_prefix(&rn->p)
-                   && !rnh_resolve_via_default(p.family))
+                   && !rnh_resolve_via_default(p.family)) {
+                       if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                               zlog_debug(
+                                       "\t:%s: Resolved against default route",
+                                       __PRETTY_FUNCTION__);
                        return 0;
+               }
 
                dest = rib_dest_from_rnode(rn);
                if (dest && dest->selected_fib
@@ -540,6 +569,9 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
                        }
                        if (resolved && set)
                                re->nexthop_mtu = match->mtu;
+                       if (!resolved && IS_ZEBRA_DEBUG_RIB_DETAILED)
+                               zlog_debug("\t%s: Recursion failed to find",
+                                          __PRETTY_FUNCTION__);
                        return resolved;
                } else if (re->type == ZEBRA_ROUTE_STATIC) {
                        resolved = 0;
@@ -558,6 +590,11 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
                        }
                        if (resolved && set)
                                re->nexthop_mtu = match->mtu;
+
+                       if (!resolved && IS_ZEBRA_DEBUG_RIB_DETAILED)
+                               zlog_debug(
+                                       "\t%s: Static route unable to resolve",
+                                       __PRETTY_FUNCTION__);
                        return resolved;
                } else {
                        return 0;
@@ -900,8 +937,12 @@ static unsigned nexthop_active_check(struct route_node *rn,
        default:
                break;
        }
-       if (!CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_ACTIVE))
+       if (!CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_ACTIVE)) {
+               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                       zlog_debug("\t%s: Unable to find a active nexthop",
+                                  __PRETTY_FUNCTION__);
                return 0;
+       }
 
        /* XXX: What exactly do those checks do? Do we support
         * e.g. IPv4 routes with IPv6 nexthops or vice versa? */