BFD: Option to specify which class of BFD sessions are accepted

Allows to configure IPv4/IPv6-only or direct/multihop-only BFD protocol
instances.

doc/bird.sgml

@@ -1955,6 +1955,7 @@ milliseconds.
 
 <code>
 protocol bfd [&lt;name&gt;] {
+	accept [ipv4|ipv6] [direct|multihop];
 	interface &lt;interface pattern&gt; {
 		interval &lt;time&gt;;
 		min rx interval &lt;time&gt;;
@@ -1989,6 +1990,14 @@ protocol bfd [&lt;name&gt;] {
 </code>
 
 <descrip>
+	<tag><label id="bfd-accept">accept [ipv4|ipv6] [direct|multihop]</tag>
+	A BFD protocol instance accepts (by default) all BFD session requests
+	(with regard to VRF restrictions, see above). This option controls
+	whether IPv4 / IPv6 and direct / multihop session requests are accepted
+	(and which listening sockets are opened). It can be used, for example,
+	to configure separate BFD protocol instances for IPv4 and for IPv6
+	sessions.
+
 	<tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
 	Interface definitions allow to specify options for sessions associated
 	with such interfaces and also may contain interface specific options.

proto/bfd/bfd.c

@@ -624,9 +624,17 @@ bfd_request_notify(struct bfd_request *req, u8 state, u8 diag)
 static int
 bfd_add_request(struct bfd_proto *p, struct bfd_request *req)
 {
+  struct bfd_config *cf = (struct bfd_config *) (p->p.cf);
+
   if (p->p.vrf_set && (p->p.vrf != req->vrf))
     return 0;
 
+  if (ipa_is_ip4(req->addr) ? !cf->accept_ipv4 : !cf->accept_ipv6)
+    return 0;
+
+  if (req->iface ? !cf->accept_direct : !cf->accept_multihop)
+    return 0;
+
   struct bfd_session *s = bfd_find_session_by_addr(p, req->addr);
   u8 state, diag;
 
@@ -986,10 +994,19 @@ bfd_start(struct proto *P)
   add_tail(&bfd_proto_list, &p->bfd_node);
 
   birdloop_enter(p->loop);
-  p->rx4_1 = bfd_open_rx_sk(p, 0, SK_IPV4);
-  p->rx4_m = bfd_open_rx_sk(p, 1, SK_IPV4);
-  p->rx6_1 = bfd_open_rx_sk(p, 0, SK_IPV6);
-  p->rx6_m = bfd_open_rx_sk(p, 1, SK_IPV6);
+
+  if (cf->accept_ipv4 && cf->accept_direct)
+    p->rx4_1 = bfd_open_rx_sk(p, 0, SK_IPV4);
+
+  if (cf->accept_ipv4 && cf->accept_multihop)
+    p->rx4_m = bfd_open_rx_sk(p, 1, SK_IPV4);
+
+  if (cf->accept_ipv6 && cf->accept_direct)
+    p->rx6_1 = bfd_open_rx_sk(p, 0, SK_IPV6);
+
+  if (cf->accept_ipv6 && cf->accept_multihop)
+    p->rx6_m = bfd_open_rx_sk(p, 1, SK_IPV6);
+
   birdloop_leave(p->loop);
 
   bfd_take_requests(p);
@@ -1034,10 +1051,17 @@ static int
 bfd_reconfigure(struct proto *P, struct proto_config *c)
 {
   struct bfd_proto *p = (struct bfd_proto *) P;
-  // struct bfd_config *old = (struct bfd_config *) (P->cf);
+  struct bfd_config *old = (struct bfd_config *) (P->cf);
   struct bfd_config *new = (struct bfd_config *) c;
   struct bfd_iface *ifa;
 
+  /* TODO: Improve accept reconfiguration */
+  if ((new->accept_ipv4 != old->accept_ipv4) ||
+      (new->accept_ipv6 != old->accept_ipv6) ||
+      (new->accept_direct != old->accept_direct) ||
+      (new->accept_multihop != old->accept_multihop))
+    return 0;
+
   birdloop_mask_wakeups(p->loop);
 
   WALK_LIST(ifa, p->iface_list)

proto/bfd/bfd.h

@@ -43,6 +43,10 @@ struct bfd_config
   list patt_list;		/* List of iface configs (struct bfd_iface_config) */
   list neigh_list;		/* List of configured neighbors (struct bfd_neighbor) */
   struct bfd_iface_config *multihop; /* Multihop pseudoiface config */
+  u8 accept_ipv4;
+  u8 accept_ipv6;
+  u8 accept_direct;
+  u8 accept_multihop;
 };
 
 struct bfd_iface_config

proto/bfd/config.Y

@@ -23,7 +23,7 @@ CF_DECLS
 
 CF_KEYWORDS(BFD, MIN, IDLE, RX, TX, INTERVAL, MULTIPLIER, PASSIVE,
 	INTERFACE, MULTIHOP, NEIGHBOR, DEV, LOCAL, AUTHENTICATION,
-	NONE, SIMPLE, METICULOUS, KEYED, MD5, SHA1)
+	NONE, SIMPLE, METICULOUS, KEYED, MD5, SHA1, IPV4, IPV6, DIRECT)
 
 %type <iface> bfd_neigh_iface
 %type <a> bfd_neigh_local
@@ -38,10 +38,13 @@ bfd_proto_start: proto_start BFD
   this_proto = proto_config_new(&proto_bfd, $1);
   init_list(&BFD_CFG->patt_list);
   init_list(&BFD_CFG->neigh_list);
+  BFD_CFG->accept_ipv4 = BFD_CFG->accept_ipv6 = 1;
+  BFD_CFG->accept_direct = BFD_CFG->accept_multihop = 1;
 };
 
 bfd_proto_item:
    proto_item
+ | ACCEPT bfd_accept
  | INTERFACE bfd_iface
  | MULTIHOP bfd_multihop
  | NEIGHBOR bfd_neighbor
@@ -56,6 +59,21 @@ bfd_proto:
    bfd_proto_start proto_name '{' bfd_proto_opts '}';
 
 
+bfd_accept_item:
+   IPV4			{ BFD_CFG->accept_ipv4 = 1;  BFD_CFG->accept_ipv6 = 0; }
+ | IPV6 		{ BFD_CFG->accept_ipv4 = 0;  BFD_CFG->accept_ipv6 = 1; }
+ | DIRECT		{ BFD_CFG->accept_direct = 1;  BFD_CFG->accept_multihop = 0; }
+ | MULTIHOP		{ BFD_CFG->accept_direct = 0;  BFD_CFG->accept_multihop = 1; }
+ ;
+
+bfd_accept:
+   {
+     BFD_CFG->accept_ipv4 = BFD_CFG->accept_ipv6 = 1;
+     BFD_CFG->accept_direct = BFD_CFG->accept_multihop = 1;
+   }
+ | bfd_accept bfd_accept_item
+
+
 bfd_iface_start:
 {
   this_ipatt = cfg_allocz(sizeof(struct bfd_iface_config));