Babel: Add support for dual-stack IPv4/IPv6 operation

This adds support for dual-stack v4/v6 operation to the Babel protocol.
Routing messages will be exchanged over IPv6, but IPv4 routes can be
carried in the messages being exchanged. This matches how the reference
Babel implementation (babeld) works.

The nexthop address for v4 can be configured per interface, and will
default to the first available IPv4 address on the given interface. For
symmetry, a configuration option to configure the IPv6 nexthop address
is also added.

Thanks to Toke Høiland-Jørgensen <toke@toke.dk> for the patch.

1 files changed, 120 insertions, 36 deletions

diff --git a/proto/babel/babel.c b/proto/babel/babel.c
index 1b1d9f62..67a59df6 100644
--- a/proto/babel/babel.c
+++ b/proto/babel/babel.c
@@ -78,13 +78,15 @@ babel_init_entry(void *E)
 static inline struct babel_entry *
 babel_find_entry(struct babel_proto *p, const net_addr *n)
 {
-  return fib_find(&p->rtable, n);
+  struct fib *rtable = (n->type == NET_IP4) ? &p->ip4_rtable : &p->ip6_rtable;
+  return fib_find(rtable, n);
 }
 
 static struct babel_entry *
 babel_get_entry(struct babel_proto *p, const net_addr *n)
 {
-  struct babel_entry *e = fib_get(&p->rtable, n);
+  struct fib *rtable = (n->type == NET_IP4) ? &p->ip4_rtable : &p->ip6_rtable;
+  struct babel_entry *e = fib_get(rtable, n);
   e->proto = p;
   return e;
 }
@@ -224,15 +226,15 @@ babel_refresh_route(struct babel_route *r)
 }
 
 static void
-babel_expire_routes(struct babel_proto *p)
+babel_expire_routes_(struct babel_proto *p UNUSED, struct fib *rtable)
 {
   struct babel_route *r, *rx;
   struct fib_iterator fit;
 
-  FIB_ITERATE_INIT(&fit, &p->rtable);
+  FIB_ITERATE_INIT(&fit, rtable);
 
 loop:
-  FIB_ITERATE_START(&p->rtable, &fit, struct babel_entry, e)
+  FIB_ITERATE_START(rtable, &fit, struct babel_entry, e)
   {
     int changed = 0;
 
@@ -253,7 +255,7 @@ loop:
       /*
        * We have to restart the iteration because there may be a cascade of
        * synchronous events babel_select_route() -> nest table change ->
-       * babel_rt_notify() -> p->rtable change, invalidating hidden variables.
+       * babel_rt_notify() -> rtable change, invalidating hidden variables.
        */
 
       FIB_ITERATE_PUT(&fit);
@@ -267,13 +269,20 @@ loop:
     if (EMPTY_LIST(e->sources) && EMPTY_LIST(e->routes))
     {
       FIB_ITERATE_PUT(&fit);
-      fib_delete(&p->rtable, e);
+      fib_delete(rtable, e);
       goto loop;
     }
   }
   FIB_ITERATE_END;
 }
 
+static void
+babel_expire_routes(struct babel_proto *p)
+{
+  babel_expire_routes_(p, &p->ip4_rtable);
+  babel_expire_routes_(p, &p->ip6_rtable);
+}
+
 static struct babel_neighbor *
 babel_find_neighbor(struct babel_iface *ifa, ip_addr addr)
 {
@@ -468,6 +477,7 @@ static void
 babel_announce_rte(struct babel_proto *p, struct babel_entry *e)
 {
   struct babel_route *r = e->selected_in;
+  struct channel *c = (e->n.addr->type == NET_IP4) ? p->ip4_channel : p->ip6_channel;
 
   if (r)
   {
@@ -490,12 +500,12 @@ babel_announce_rte(struct babel_proto *p, struct babel_entry *e)
     rte->u.babel.router_id = r->router_id;
     rte->pflags = 0;
 
-    rte_update(&p->p, e->n.addr, rte);
+    rte_update2(c, e->n.addr, rte, p->p.main_source);
   }
   else
   {
     /* Retraction */
-    rte_update(&p->p, e->n.addr, NULL);
+    rte_update2(c, e->n.addr, NULL, p->p.main_source);
   }
 }
 
@@ -740,11 +750,11 @@ babel_unicast_seqno_request(struct babel_route *r)
  * transmitted entry is updated.
  */
 static void
-babel_send_update(struct babel_iface *ifa, bird_clock_t changed)
+babel_send_update_(struct babel_iface *ifa, bird_clock_t changed, struct fib *rtable)
 {
   struct babel_proto *p = ifa->proto;
 
-  FIB_WALK(&p->rtable, struct babel_entry, e)
+  FIB_WALK(rtable, struct babel_entry, e)
   {
     struct babel_route *r = e->selected_out;
 
@@ -774,6 +784,9 @@ babel_send_update(struct babel_iface *ifa, bird_clock_t changed)
     msg.update.router_id = r->router_id;
     net_copy(&msg.update.net, e->n.addr);
 
+    msg.update.next_hop = ((e->n.addr->type == NET_IP4) ?
+			   ifa->next_hop_ip4 : ifa->next_hop_ip6);
+
     babel_enqueue(&msg, ifa);
 
     /* Update feasibility distance for redistributed routes */
@@ -794,6 +807,15 @@ babel_send_update(struct babel_iface *ifa, bird_clock_t changed)
 }
 
 static void
+babel_send_update(struct babel_iface *ifa, bird_clock_t changed)
+{
+  struct babel_proto *p = ifa->proto;
+
+  babel_send_update_(ifa, changed, &p->ip4_rtable);
+  babel_send_update_(ifa, changed, &p->ip6_rtable);
+}
+
+static void
 babel_trigger_iface_update(struct babel_iface *ifa)
 {
   struct babel_proto *p = ifa->proto;
@@ -1073,6 +1095,13 @@ babel_handle_update(union babel_msg *m, struct babel_iface *ifa)
     return;
   }
 
+  struct channel *c = (msg->net.type == NET_IP4) ? p->ip4_channel : p->ip6_channel;
+  if (!c || (c->channel_state != CS_UP))
+  {
+    DBG("Babel: Ignoring update for inactive address family.\n");
+    return;
+  }
+
   /*
    * RFC section 3.5.4:
    *
@@ -1475,14 +1504,26 @@ babel_add_iface(struct babel_proto *p, struct iface *new, struct babel_iface_con
 
   add_tail(&p->interfaces, NODE ifa);
 
+  ip_addr addr4 = IPA_NONE;
   struct ifa *addr;
   WALK_LIST(addr, new->addrs)
+  {
     if (ipa_is_link_local(addr->ip))
       ifa->addr = addr->ip;
 
+    if (ipa_zero(addr4) && ipa_is_ip4(addr->ip))
+      addr4 = addr->ip;
+  }
+
+  ifa->next_hop_ip4 = ipa_nonzero(ic->next_hop_ip4) ? ic->next_hop_ip4 : addr4;
+  ifa->next_hop_ip6 = ipa_nonzero(ic->next_hop_ip6) ? ic->next_hop_ip6 : ifa->addr;
+
   if (ipa_zero(ifa->addr))
     log(L_WARN "%s: Cannot find link-local addr on %s", p->p.name, new->name);
 
+  if (ipa_zero(ifa->next_hop_ip4) && p->ip4_channel)
+    log(L_WARN "%s: Cannot find IPv4 next hop addr on %s", p->p.name, new->name);
+
   init_list(&ifa->neigh_list);
   ifa->hello_seqno = 1;
 
@@ -1574,6 +1615,26 @@ babel_reconfigure_iface(struct babel_proto *p, struct babel_iface *ifa, struct b
 
   ifa->cf = new;
 
+  if (ipa_nonzero(new->next_hop_ip4))
+    ifa->next_hop_ip4 = new->next_hop_ip4;
+  else
+  {
+    ifa->next_hop_ip4 = IPA_NONE;
+
+    struct ifa *addr;
+    WALK_LIST(addr, ifa->iface->addrs)
+      if (ipa_is_ip4(addr->ip))
+      {
+	ifa->next_hop_ip4 = addr->ip;
+	break;
+      }
+  }
+
+  ifa->next_hop_ip6 = ipa_nonzero(new->next_hop_ip6) ? new->next_hop_ip6 : ifa->addr;
+
+  if (ipa_zero(ifa->next_hop_ip4) && p->ip4_channel)
+    log(L_WARN "%s: Cannot find IPv4 next hop addr on %s", p->p.name, ifa->ifname);
+
   if (ifa->next_hello > (now + new->hello_interval))
     ifa->next_hello = now + (random() % new->hello_interval) + 1;
 
@@ -1680,9 +1741,10 @@ babel_dump_iface(struct babel_iface *ifa)
 {
   struct babel_neighbor *n;
 
-  debug("Babel: Interface %s addr %I rxcost %d type %d hello seqno %d intervals %d %d\n",
+  debug("Babel: Interface %s addr %I rxcost %d type %d hello seqno %d intervals %d %d",
 	ifa->ifname, ifa->addr, ifa->cf->rxcost, ifa->cf->type, ifa->hello_seqno,
 	ifa->cf->hello_interval, ifa->cf->update_interval);
+  debug(" next hop v4 %I next hop v6 %I\n", ifa->next_hop_ip4, ifa->next_hop_ip6);
 
   WALK_LIST(n, ifa->neigh_list)
   { debug(" "); babel_dump_neighbor(n); }
@@ -1699,7 +1761,12 @@ babel_dump(struct proto *P)
   WALK_LIST(ifa, p->interfaces)
     babel_dump_iface(ifa);
 
-  FIB_WALK(&p->rtable, struct babel_entry, e)
+  FIB_WALK(&p->ip4_rtable, struct babel_entry, e)
+  {
+    babel_dump_entry(e);
+  }
+  FIB_WALK_END;
+  FIB_WALK(&p->ip6_rtable, struct babel_entry, e)
   {
     babel_dump_entry(e);
   }
@@ -1749,8 +1816,9 @@ babel_show_interfaces(struct proto *P, char *iff)
   }
 
   cli_msg(-1023, "%s:", p->p.name);
-  cli_msg(-1023, "%-10s %-6s %7s %6s %6s",
-	  "Interface", "State", "RX cost", "Nbrs", "Timer");
+  cli_msg(-1023, "%-10s %-6s %7s %6s %6s %-15s %s",
+	  "Interface", "State", "RX cost", "Nbrs", "Timer",
+	  "Next hop (v4)", "Next hop (v6)");
 
   WALK_LIST(ifa, p->interfaces)
   {
@@ -1762,8 +1830,10 @@ babel_show_interfaces(struct proto *P, char *iff)
 	nbrs++;
 
     int timer = MIN(ifa->next_regular, ifa->next_hello) - now;
-    cli_msg(-1023, "%-10s %-6s %7u %6u %6u",
-	    ifa->iface->name, (ifa->up ? "Up" : "Down"), ifa->cf->rxcost, nbrs, MAX(timer, 0));
+    cli_msg(-1023, "%-10s %-6s %7u %6u %6u %-15I %I",
+	    ifa->iface->name, (ifa->up ? "Up" : "Down"),
+	    ifa->cf->rxcost, nbrs, MAX(timer, 0),
+	    ifa->next_hop_ip4, ifa->next_hop_ip6);
   }
 
   cli_msg(0, "");
@@ -1808,27 +1878,15 @@ babel_show_neighbors(struct proto *P, char *iff)
   cli_msg(0, "");
 }
 
-void
-babel_show_entries(struct proto *P)
+static void
+babel_show_entries_(struct babel_proto *p, struct fib *rtable)
 {
-  struct babel_proto *p = (void *) P;
   struct babel_source *s = NULL;
   struct babel_route *r = NULL;
 
   char ridbuf[ROUTER_ID_64_LENGTH+1];
 
-  if (p->p.proto_state != PS_UP)
-  {
-    cli_msg(-1025, "%s: is not up", p->p.name);
-    cli_msg(0, "");
-    return;
-  }
-
-  cli_msg(-1025, "%s:", p->p.name);
-  cli_msg(-1025, "%-29s %-23s %6s %5s %7s %7s",
-	  "Prefix", "Router ID", "Metric", "Seqno", "Expires", "Sources");
-
-  FIB_WALK(&p->rtable, struct babel_entry, e)
+  FIB_WALK(rtable, struct babel_entry, e)
   {
     r = e->selected_in ? e->selected_in : e->selected_out;
 
@@ -1853,6 +1911,26 @@ babel_show_entries(struct proto *P)
     }
   }
   FIB_WALK_END;
+}
+
+void
+babel_show_entries(struct proto *P)
+{
+  struct babel_proto *p = (void *) P;
+
+  if (p->p.proto_state != PS_UP)
+  {
+    cli_msg(-1025, "%s: is not up", p->p.name);
+    cli_msg(0, "");
+    return;
+  }
+
+  cli_msg(-1025, "%s:", p->p.name);
+  cli_msg(-1025, "%-29s %-23s %6s %5s %7s %7s",
+	  "Prefix", "Router ID", "Metric", "Seqno", "Expires", "Sources");
+
+  babel_show_entries_(p, &p->ip4_rtable);
+  babel_show_entries_(p, &p->ip6_rtable);
 
   cli_msg(0, "");
 }
@@ -2028,8 +2106,10 @@ static struct proto *
 babel_init(struct proto_config *CF)
 {
   struct proto *P = proto_new(CF);
+  struct babel_proto *p = (void *) P;
 
-  P->main_channel = proto_add_channel(P, proto_cf_main_channel(CF));
+  proto_configure_channel(P, &p->ip4_channel, proto_cf_find_channel(CF, NET_IP4));
+  proto_configure_channel(P, &p->ip6_channel, proto_cf_find_channel(CF, NET_IP6));
 
   P->if_notify = babel_if_notify;
   P->rt_notify = babel_rt_notify;
@@ -2048,8 +2128,11 @@ babel_start(struct proto *P)
   struct babel_proto *p = (void *) P;
   struct babel_config *cf = (void *) P->cf;
 
-  fib_init(&p->rtable, P->pool, NET_IP6, sizeof(struct babel_entry),
+  fib_init(&p->ip4_rtable, P->pool, NET_IP4, sizeof(struct babel_entry),
 	   OFFSETOF(struct babel_entry, n), 0, babel_init_entry);
+  fib_init(&p->ip6_rtable, P->pool, NET_IP6, sizeof(struct babel_entry),
+	   OFFSETOF(struct babel_entry, n), 0, babel_init_entry);
+
   init_list(&p->interfaces);
   p->timer = tm_new_set(P->pool, babel_timer, p, 0, 1);
   tm_start(p->timer, 2);
@@ -2099,7 +2182,8 @@ babel_reconfigure(struct proto *P, struct proto_config *CF)
 
   TRACE(D_EVENTS, "Reconfiguring");
 
-  if (!proto_configure_channel(P, &P->main_channel, proto_cf_main_channel(CF)))
+  if (!proto_configure_channel(P, &p->ip4_channel, proto_cf_find_channel(CF, NET_IP4)) ||
+      !proto_configure_channel(P, &p->ip6_channel, proto_cf_find_channel(CF, NET_IP6)))
     return 0;
 
   p->p.cf = CF;
@@ -2117,7 +2201,7 @@ struct protocol proto_babel = {
   .template =		"babel%d",
   .attr_class =		EAP_BABEL,
   .preference =		DEF_PREF_BABEL,
-  .channel_mask =	NB_IP6,
+  .channel_mask =	NB_IP,
   .proto_size =		sizeof(struct babel_proto),
   .config_size =	sizeof(struct babel_config),
   .init =		babel_init,