not really used, I think?

Index: ext/tinydtls/tests/dtls-client.c
--- ext/tinydtls/tests/dtls-client.c.orig
+++ ext/tinydtls/tests/dtls-client.c
@@ -537,8 +537,8 @@ main(int argc, char **argv) {
     }
   }
   else {
-    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));
     }
   }
 
