Allocate neighbour later.

Only allocate the neighbour after all the basic sanity checks have been
performed.  This is important in the HMAC branch.

message.c

@@ -480,12 +480,6 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         return;
     }
 
-    neigh = find_neighbour(from, ifp);
-    if(neigh == NULL) {
-        fprintf(stderr, "Couldn't allocate neighbour.\n");
-        return;
-    }
-
     DO_NTOHS(bodylen, packet + 2);
 
     if(bodylen + 4 > packetlen) {
@@ -494,6 +488,12 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         bodylen = packetlen - 4;
     }
 
+    neigh = find_neighbour(from, ifp);
+    if(neigh == NULL) {
+        fprintf(stderr, "Couldn't allocate neighbour.\n");
+        return;
+    }
+
     i = 0;
     while(i < bodylen) {
         message = packet + 4 + i;