Added debugging of communication between protocols and routing tables.

Just ask for "debug routes" if you want to see the routes and "debug filters"
if you want even the rejected ones.

TODO

 Core
 ~~~~
 - debug: interfaces
-- debug: route updates
 - debug: static
 - debug: pipe
 - debug: krt
@@ -9,9 +8,6 @@ Core
 - static: check validity of route destination?
 - static: allow specifying a per-route filter program for setting route attributes?
 
-- rte_update: check whether all bits not covered by masklen are zero
-- rte_update: debug mode
-
 - krt: rescan interfaces when route addition fails?
 
 - tagging of external routes?

nest/rt-table.c

@@ -27,6 +27,8 @@ static linpool *rte_update_pool;
 static pool *rt_table_pool;
 static list routing_tables;
 
+static void rt_format_via(rte *e, byte *via);
+
 static void
 rte_init(struct fib_node *N)
 {
@@ -93,6 +95,29 @@ rte_better(rte *new, rte *old)
   return 0;
 }
 
+static void
+rte_trace(struct proto *p, rte *e, int dir, char *msg)
+{
+  byte via[STD_ADDRESS_P_LENGTH+32];
+
+  rt_format_via(e, via);
+  log(L_TRACE "%s %c %s %I/%d %s", p->name, dir, msg, e->net->n.prefix, e->net->n.pxlen, via);
+}
+
+static inline void
+rte_trace_in(unsigned int flag, struct proto *p, rte *e, char *msg)
+{
+  if (p->debug & flag)
+    rte_trace(p, e, '<', msg);
+}
+
+static inline void
+rte_trace_out(unsigned int flag, struct proto *p, rte *e, char *msg)
+{
+  if (p->debug & flag)
+    rte_trace(p, e, '>', msg);
+}
+
 static inline void
 do_rte_announce(struct announce_hook *a, net *net, rte *new, rte *old, ea_list *tmpa, int class)
 {
@@ -103,13 +128,24 @@ do_rte_announce(struct announce_hook *a, net *net, rte *new, rte *old, ea_list *
   if (new)
     {
       int ok;
-      if ((class & IADDR_SCOPE_MASK) < p->min_scope ||
-	  (ok = p->import_control ? p->import_control(p, &new, &tmpa, rte_update_pool) : 0) < 0 ||
-	  (!ok && (p->out_filter == FILTER_REJECT ||
-		   p->out_filter && f_run(p->out_filter, &new, &tmpa, rte_update_pool) > F_ACCEPT)
-	  )
-	 )
-	new = NULL;
+      if ((class & IADDR_SCOPE_MASK) < p->min_scope)
+	{
+	  rte_trace_out(D_FILTERS, p, new, "out of scope");
+	  new = NULL;
+	}
+      else if ((ok = p->import_control ? p->import_control(p, &new, &tmpa, rte_update_pool) : 0) < 0)
+	{
+	  rte_trace_out(D_FILTERS, p, new, "rejected by protocol");
+	  new = NULL;
+	}
+      else if (ok)
+	rte_trace_out(D_FILTERS, p, new, "forced accept by protocol");
+      else if (p->out_filter == FILTER_REJECT ||
+	       p->out_filter && f_run(p->out_filter, &new, &tmpa, rte_update_pool) > F_ACCEPT)
+	{
+	  rte_trace_out(D_FILTERS, p, new, "filtered out");
+	  new = NULL;
+	}
     }
   if (old && p->out_filter)
     {
@@ -123,6 +159,15 @@ do_rte_announce(struct announce_hook *a, net *net, rte *new, rte *old, ea_list *
 	    old = NULL;
 	}
     }
+  if (p->debug & D_ROUTES)
+    {
+      if (new && old)
+	rte_trace_out(D_ROUTES, p, new, "replaced");
+      else if (new)
+	rte_trace_out(D_ROUTES, p, new, "added");
+      else
+	rte_trace_out(D_ROUTES, p, old, "removed");
+    }
   if (new || old)
     p->rt_notify(p, net, new, old, tmpa);
   if (new && new != new0)	/* Discard temporary rte's */
@@ -177,7 +222,12 @@ rte_validate(rte *e)
   int c;
   net *n = e->net;
 
-  ASSERT(!ipa_nonzero(ipa_and(n->n.prefix, ipa_not(ipa_mkmask(n->n.pxlen)))));
+  if (ipa_nonzero(ipa_and(n->n.prefix, ipa_not(ipa_mkmask(n->n.pxlen)))))
+    {
+      log(L_BUG "Ignoring bogus prefix %I/%d received via %s",
+	  n->n.prefix, n->n.pxlen, e->attrs->proto->name);
+      return 0;
+    }
   if (n->n.pxlen)
     {
       c = ipa_classify(n->n.prefix);
@@ -238,6 +288,7 @@ rte_recalculate(rtable *table, net *net, struct proto *p, rte *new, ea_list *tmp
       rte_announce(table, net, new, old_best, tmpa);
       new->next = net->routes;
       net->routes = new;
+      rte_trace_in(D_ROUTES, p, new, "added [best]");
     }
   else
     {
@@ -272,6 +323,16 @@ rte_recalculate(rtable *table, net *net, struct proto *p, rte *new, ea_list *tmp
 	{
 	  new->next = old_best->next;
 	  old_best->next = new;
+	  rte_trace_in(D_ROUTES, p, new, "added");
+	}
+      else if (old && (p->debug & D_ROUTES))
+	{
+	  if (old != old_best)
+	    rte_trace_in(D_ROUTES, p, old, "removed");
+	  else if (net->routes)
+	    rte_trace_in(D_ROUTES, p, old, "removed [replaced]");
+	  else
+	    rte_trace_in(D_ROUTES, p, old, "removed [sole]");
 	}
     }
   if (old)
@@ -311,8 +372,16 @@ rte_update(rtable *table, net *net, struct proto *p, rte *new)
   rte_update_lock();
   if (new)
     {
-      if (!rte_validate(new) || p->in_filter == FILTER_REJECT)
-	goto drop;
+      if (!rte_validate(new))
+	{
+	  rte_trace_in(D_FILTERS, p, new, "invalid");
+	  goto drop;
+	}
+      if (p->in_filter == FILTER_REJECT)
+	{
+	  rte_trace_in(D_FILTERS, p, new, "filtered out");
+	  goto drop;
+	}
       if (p->make_tmp_attrs)
 	tmpa = p->make_tmp_attrs(new, rte_update_pool);
       if (p->in_filter)
@@ -320,7 +389,10 @@ rte_update(rtable *table, net *net, struct proto *p, rte *new)
 	  ea_list *old_tmpa = tmpa;
 	  int fr = f_run(p->in_filter, &new, &tmpa, rte_update_pool);
 	  if (fr > F_ACCEPT)
-	    goto drop;
+	    {
+	      rte_trace_in(D_FILTERS, p, new, "filtered out");
+	      goto drop;
+	    }
 	  if (tmpa != old_tmpa && p->store_tmp_attrs)
 	    p->store_tmp_attrs(new, tmpa);
 	}
@@ -340,8 +412,11 @@ drop:
 void
 rte_discard(rtable *t, rte *old)	/* Non-filtered route deletion, used during garbage collection */
 {
+  net *n = old->net;
+  struct proto *p = old->attrs->proto;
+
   rte_update_lock();
-  rte_recalculate(t, old->net, old->attrs->proto, NULL, NULL);
+  rte_recalculate(t, n, p, NULL, NULL);
   rte_update_unlock();
 }
 
@@ -567,10 +642,8 @@ rt_commit(struct config *new, struct config *old)
  */
 
 static void
-rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d)
+rt_format_via(rte *e, byte *via)
 {
-  byte via[STD_ADDRESS_P_LENGTH+32], from[STD_ADDRESS_P_LENGTH];
-  byte tm[TM_RELTIME_BUFFER_SIZE], info[256];
   rta *a = e->attrs;
 
   switch (a->dest)
@@ -582,6 +655,16 @@ rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d)
     case RTD_PROHIBIT:	bsprintf(via, "prohibited"); break;
     default:		bsprintf(via, "???");
     }
+}
+
+static void
+rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d)
+{
+  byte via[STD_ADDRESS_P_LENGTH+32], from[STD_ADDRESS_P_LENGTH];
+  byte tm[TM_RELTIME_BUFFER_SIZE], info[256];
+  rta *a = e->attrs;
+
+  rt_format_via(e, via);
   tm_format_reltime(tm, e->lastmod);
   if (ipa_nonzero(a->from) && !ipa_equal(a->from, a->gw))
     bsprintf(from, " from %I", a->from);