BFD: Fixes crash after socket error

Thanks to Thomas King for the bugreport.

proto/bfd/bfd.c

@@ -43,7 +43,7 @@
  * the needs of BFD sessions. When a new session is created, it requests a
  * proper BFD interface by function bfd_get_iface(), which either finds an
  * existing one in &iface_list (from &bfd_proto) or allocates a new one. When a
- * session is removed, an associated iface is dicharged by bfd_free_iface().
+ * session is removed, an associated iface is discharged by bfd_free_iface().
  *
  * BFD requests are the external API for the other protocols. When a protocol
  * wants a BFD session, it calls bfd_request_session(), which creates a
@@ -62,7 +62,7 @@
  * configuration (like static routes in the static protocol). BFD neighbors are
  * handled by BFD protocol like it is a BFD client -- when a BFD neighbor is
  * ready, the protocol just creates a BFD request like any other protocol.
- * 
+ *
  * The protocol uses a new generic event loop (structure &birdloop) from |io.c|,
  * which supports sockets, timers and events like the main loop. Timers
  * (structure &timer2) are new microsecond based timers, while sockets and
@@ -129,11 +129,11 @@ static inline void bfd_notify_kick(struct bfd_proto *p);
  *	BFD sessions
  */
 
-static void 
+static void
 bfd_session_update_state(struct bfd_session *s, uint state, uint diag)
 {
   struct bfd_proto *p = s->ifa->bfd;
-  uint old_state = s->loc_state; 
+  uint old_state = s->loc_state;
   int notify;
 
   if (state == old_state)
@@ -201,8 +201,8 @@ bfd_session_control_tx_timer(struct bfd_session *s, int reset)
   if (s->passive && (s->rem_id == 0))
     goto stop;
 
-  if (s->rem_demand_mode && 
-      !s->poll_active && 
+  if (s->rem_demand_mode &&
+      !s->poll_active &&
       (s->loc_state == BFD_STATE_UP) &&
       (s->rem_state == BFD_STATE_UP))
     goto stop;
@@ -303,7 +303,7 @@ bfd_session_process_ctl(struct bfd_session *s, u8 flags, u32 old_tx_int, u32 old
     bfd_send_ctl(s->ifa->bfd, s, 1);
 }
 
-static void 
+static void
 bfd_session_timeout(struct bfd_session *s)
 {
   struct bfd_proto *p = s->ifa->bfd;
@@ -353,7 +353,7 @@ bfd_session_set_min_rx(struct bfd_session *s, u32 val)
   if (val == s->req_min_rx_new)
     return;
 
-  s->req_min_rx_new = val; 
+  s->req_min_rx_new = val;
 
   /* Postpone timer update if req_min_rx_int decreases and the session is up */
   if ((s->loc_state != BFD_STATE_UP) || (val > s->req_min_rx_int))
@@ -575,9 +575,13 @@ bfd_free_iface(struct bfd_iface *ifa)
   if (!ifa || --ifa->uc)
     return;
 
+  if (ifa->sk)
+  {
+    sk_stop(ifa->sk);
+    rfree(ifa->sk);
+  }
+
   rem_node(&ifa->n);
-  sk_stop(ifa->sk);
-  rfree(ifa->sk);
   mb_free(ifa);
 }
 
@@ -873,7 +877,7 @@ bfd_notify_hook(sock *sk, int len)
     diag = s->loc_diag;
     bfd_unlock_sessions(p);
 
-    /* FIXME: convert to btime and move to bfd_session_update_state() */ 
+    /* FIXME: convert to btime and move to bfd_session_update_state() */
     s->last_state_change = now;
 
     s->notify_running = 1;
@@ -1092,7 +1096,7 @@ bfd_show_sessions(struct proto *P)
     /* FIXME: this is thread-unsafe, but perhaps harmless */
     state = s->loc_state;
     diag = s->loc_diag;
-    ifname = (s->ifa && s->ifa->sk->iface) ? s->ifa->sk->iface->name : "---";
+    ifname = (s->ifa && s->ifa->iface) ? s->ifa->iface->name : "---";
     tx_int = s->last_tx ? (MAX(s->des_min_tx_int, s->rem_min_rx_int) TO_MS) : 0;
     timeout = (MAX(s->req_min_rx_int, s->rem_min_tx_int) TO_MS) * s->rem_detect_mult;
 

proto/bfd/packets.c

@@ -63,9 +63,13 @@ void
 bfd_send_ctl(struct bfd_proto *p, struct bfd_session *s, int final)
 {
   sock *sk = s->ifa->sk;
-  struct bfd_ctl_packet *pkt = (struct bfd_ctl_packet *) sk->tbuf;
+  struct bfd_ctl_packet *pkt;
   char fb[8];
 
+  if (!sk)
+    return;
+
+  pkt = (struct bfd_ctl_packet *) sk->tbuf;
   pkt->vdiag = bfd_pack_vdiag(1, s->loc_diag);
   pkt->flags = bfd_pack_flags(s->loc_state, 0);
   pkt->detect_mult = s->detect_mult;
@@ -139,7 +143,7 @@ bfd_rx_hook(sock *sk, int len)
     u8 ps = bfd_pkt_get_state(pkt);
     if (ps > BFD_STATE_DOWN)
       DROP("invalid init state", ps);
-      
+
     s = bfd_find_session_by_addr(p, sk->faddr);
 
     /* FIXME: better session matching and message */