Nest: Fix bug in device proto

If an interface address notification is received during device protocol
shutdown/restart, BIRD crashed.

Thanks to Wei Huang for the bugreport.

sysdep/linux/netlink.c

@@ -1116,12 +1116,14 @@ nl_async_msg(struct nlmsghdr *h)
     case RTM_NEWLINK:
     case RTM_DELLINK:
       DBG("KRT: Received async link notification (%d)\n", h->nlmsg_type);
-      nl_parse_link(h, 0);
+      if (kif_proto)
+	nl_parse_link(h, 0);
       break;
     case RTM_NEWADDR:
     case RTM_DELADDR:
       DBG("KRT: Received async address notification (%d)\n", h->nlmsg_type);
-      nl_parse_addr(h, 0);
+      if (kif_proto)
+	nl_parse_addr(h, 0);
       break;
     default:
       DBG("KRT: Received unknown async notification (%d)\n", h->nlmsg_type);

sysdep/unix/krt.c

@@ -84,8 +84,8 @@ krt_io_init(void)
  *	Interfaces
  */
 
+struct kif_proto *kif_proto;
 static struct kif_config *kif_cf;
-static struct kif_proto *kif_proto;
 static timer *kif_scan_timer;
 static bird_clock_t kif_last_shot;
 

sysdep/unix/krt.h

@@ -112,6 +112,8 @@ struct kif_proto {
   struct kif_state sys;		/* Sysdep state */
 };
 
+struct kif_proto *kif_proto;
+
 #define KIF_CF ((struct kif_config *)p->p.cf)
 
 struct proto_config * krt_init_config(int class);