not really used, I think?

Index: ext/tinydtls/tests/dtls-server.c
--- ext/tinydtls/tests/dtls-server.c.orig
+++ ext/tinydtls/tests/dtls-server.c
@@ -426,8 +426,8 @@ main(int argc, char **argv) {
       dtls_alert("setsockopt IPV6_PKTINFO: %s\n", strerror(errno));
     }
   }
-  if (setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on)) < 0) {
-    dtls_alert("setsockopt IP_PKTINFO: %s\n", strerror(errno));
+  if (setsockopt(fd, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on)) < 0) {
+    dtls_alert("setsockopt IP_RECVDSTADDR: %s\n", strerror(errno));
   }
 
   if (bind(fd, (struct sockaddr *)&listen_addr,
