bfdd: don't enable sessions without local-address

When the local-address configured by the peer doesn't exist, then we
must observe the session until the mentioned address comes up.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

bfdd/bfd.c

@@ -162,6 +162,13 @@ int bfd_session_enable(struct bfd_session *bs)
 	    && BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_MH) == 0)
 		bs->ifp = ifp;
 
+	/* Sanity check: don't leak open sockets. */
+	if (bs->sock != -1) {
+		zlog_debug("session-enable: previous socket open");
+		close(bs->sock);
+		bs->sock = -1;
+	}
+
 	/*
 	 * Get socket for transmitting control packets.  Note that if we
 	 * could use the destination port (3784) for the source
@@ -170,11 +177,11 @@ int bfd_session_enable(struct bfd_session *bs)
 	if (BFD_CHECK_FLAG(bs->flags, BFD_SESS_FLAG_IPV6) == 0) {
 		psock = bp_peer_socket(bs);
 		if (psock == -1)
-			return -1;
+			return 0;
 	} else {
 		psock = bp_peer_socketv6(bs);
 		if (psock == -1)
-			return -1;
+			return 0;
 	}
 
 	/*
@@ -662,10 +669,6 @@ struct bfd_session *ptm_bfd_sess_new(struct bfd_peer_cfg *bpc)
 		strlcpy(bfd->key.vrfname, bpc->bpc_vrfname,
 			sizeof(bfd->key.vrfname));
 
-	/* Add observer if we have moving parts. */
-	if (bfd->key.ifname[0] || bfd->key.vrfname[0])
-		bs_observer_add(bfd);
-
 	/* Copy remaining data. */
 	if (bpc->bpc_ipv4 == false)
 		BFD_SET_FLAG(bfd->flags, BFD_SESS_FLAG_IPV6);
@@ -708,6 +711,10 @@ struct bfd_session *ptm_bfd_sess_new(struct bfd_peer_cfg *bpc)
 		return NULL;
 	}
 
+	/* Add observer if we have moving parts. */
+	if (bfd->key.ifname[0] || bfd->key.vrfname[0] || bfd->sock == -1)
+		bs_observer_add(bfd);
+
 	/* Apply other configurations. */
 	_bfd_session_update(bfd, bpc);
 
@@ -1190,6 +1197,14 @@ int bs_observer_add(struct bfd_session *bs)
 		strlcpy(bso->bso_entryname, bs->key.vrfname,
 			sizeof(bso->bso_entryname));
 
+	/* Handle socket binding failures caused by missing local addresses. */
+	if (bs->sock == -1) {
+		bso->bso_isaddress = true;
+		bso->bso_addr.family = bs->key.family;
+		memcpy(&bso->bso_addr.u.prefix, &bs->key.local,
+		       sizeof(bs->key.local));
+	}
+
 	TAILQ_INSERT_TAIL(&bglobal.bg_obslist, bso, bso_entry);
 
 	return 0;

bfdd/bfd.h

@@ -274,7 +274,11 @@ struct bfd_state_str_list {
 struct bfd_session_observer {
 	struct bfd_session *bso_bs;
 	bool bso_isinterface;
-	char bso_entryname[MAXNAMELEN];
+	bool bso_isaddress;
+	union {
+		char bso_entryname[MAXNAMELEN];
+		struct prefix bso_addr;
+	};
 
 	TAILQ_ENTRY(bfd_session_observer) bso_entry;
 };

bfdd/bfdd_vty.c

@@ -942,7 +942,8 @@ static void _bfdd_peer_write_config(struct vty *vty, struct bfd_session *bs)
 	vty_out(vty, "\n");
 
 	if (bs->sock == -1)
-		vty_out(vty, "  ! vrf or interface doesn't exist\n");
+		vty_out(vty,
+			"  ! vrf, interface or local-address doesn't exist\n");
 
 	if (bs->detect_mult != BPC_DEF_DETECTMULTIPLIER)
 		vty_out(vty, "  detect-multiplier %d\n", bs->detect_mult);

bfdd/ptm_adapter.c

@@ -634,6 +634,48 @@ static int bfdd_interface_vrf_update(int command __attribute__((__unused__)),
 	return 0;
 }
 
+static void bfdd_sessions_enable_address(struct connected *ifc)
+{
+	struct bfd_session_observer *bso;
+	struct bfd_session *bs;
+	struct prefix prefix;
+
+	TAILQ_FOREACH(bso, &bglobal.bg_obslist, bso_entry) {
+		if (bso->bso_isaddress == false)
+			continue;
+
+		/* Skip enabled sessions. */
+		bs = bso->bso_bs;
+		if (bs->sock != -1)
+			continue;
+
+		/* Check address. */
+		prefix = bso->bso_addr;
+		prefix.prefixlen = ifc->address->prefixlen;
+		if (prefix_cmp(&prefix, ifc->address))
+			continue;
+
+		/* Try to enable it. */
+		bfd_session_enable(bs);
+	}
+}
+
+static int bfdd_interface_address_update(int cmd, struct zclient *zc,
+					 zebra_size_t len
+					 __attribute__((__unused__)),
+					 vrf_id_t vrfid)
+{
+	struct connected *ifc;
+
+	ifc = zebra_interface_address_read(cmd, zc->ibuf, vrfid);
+	if (ifc == NULL)
+		return 0;
+
+	bfdd_sessions_enable_address(ifc);
+
+	return 0;
+}
+
 void bfdd_zclient_init(struct zebra_privs_t *bfdd_priv)
 {
 	zclient = zclient_new(master, &zclient_options_default);
@@ -656,6 +698,10 @@ void bfdd_zclient_init(struct zebra_privs_t *bfdd_priv)
 
 	/* Learn about interface VRF. */
 	zclient->interface_vrf_update = bfdd_interface_vrf_update;
+
+	/* Learn about new addresses being registered. */
+	zclient->interface_address_add = bfdd_interface_address_update;
+	zclient->interface_address_delete = bfdd_interface_address_update;
 }
 
 void bfdd_zclient_stop(void)