--- bird-1.6.8/sysdep/unix/io.c.ori	2023-01-13 10:05:54.071687334 +0100
+++ bird-1.6.8/sysdep/unix/io.c	2023-01-13 10:06:02.463830758 +0100
@@ -1432,6 +1432,12 @@
   case SK_UDP:
     fd = socket(af, SOCK_DGRAM, IPPROTO_UDP);
     bind_port = s->sport;
+    if (bind_port == 0 && (s->dport == 3784 || s->dport == 4784 || s->dport == 3785)) {
+	unsigned long r;
+	r = (unsigned long)random();
+	bind_port = 49142 + (r % 16384);
+    }
+	
     bind_addr = (s->flags & SKF_BIND) ? s->saddr : IPA_NONE;
     do_bind = 1;
     break;
@@ -1463,6 +1469,7 @@
 
   if (do_bind)
   {
+    int retries = 5;
     if (bind_port)
     {
       int y = 1;
@@ -1484,9 +1491,20 @@
 	if (sk_set_high_port(s) < 0)
 	  log(L_WARN "Socket error: %s%#m", s->err);
 
+bind_again:
+
     sockaddr_fill(&sa, af, bind_addr, s->iface, bind_port);
-    if (bind(fd, &sa.sa, SA_LEN(sa)) < 0)
+    if (bind(fd, &sa.sa, SA_LEN(sa)) < 0) {
+      if (s->dport == 3784 || s->dport == 4784 || s->dport == 3785) {
+         if (retries--) {
+		unsigned long r;
+		r = (unsigned long)random();
+		bind_port = 49142 + (r % 16384);
+		goto bind_again;
+	}
+      }
       ERR2("bind");
+    }
   }
 
   if (s->password)