Nameservers should not get the unreachable status if TCP hasn't been tried yet.

Thanks to Christopher Olah and Paul Wouters (see "pyLDNS Problems" thread on the ldns-users list).

diff --git a/resolver.c b/resolver.c
index 735e6f147d15020c1fba1720a0b1c4461aeef3eb..732f2a8a776de413ecf359a57dead26c8558372f 100644 (file)
--- a/resolver.c
+++ b/resolver.c
@@ -1031,12 +1031,41 @@ ldns_resolver_query(const ldns_resolver *r, const ldns_rdf *name,
        return pkt;
 }
 
+static size_t *
+ldns_resolver_backup_rtt(ldns_resolver *r)
+{
+       size_t *new_rtt;
+       size_t *old_rtt = ldns_resolver_rtt(r);
+
+       if (old_rtt && ldns_resolver_nameserver_count(r)) {
+               new_rtt = LDNS_XMALLOC(size_t
+                               , ldns_resolver_nameserver_count(r));
+               memcpy(new_rtt, old_rtt, sizeof(size_t)
+                               * ldns_resolver_nameserver_count(r));
+               ldns_resolver_set_rtt(r, new_rtt);
+               return old_rtt;
+       }
+       return NULL;
+}
+
+static void
+ldns_resolver_restore_rtt(ldns_resolver *r, size_t *old_rtt)
+{
+       size_t *cur_rtt = ldns_resolver_rtt(r);
+
+       if (cur_rtt) {
+               LDNS_FREE(cur_rtt);
+       }
+       ldns_resolver_set_rtt(r, old_rtt);
+}
+
 ldns_status
 ldns_resolver_send_pkt(ldns_pkt **answer, ldns_resolver *r,
                                   ldns_pkt *query_pkt)
 {
        ldns_pkt *answer_pkt = NULL;
        ldns_status stat = LDNS_STATUS_OK;
+       size_t *rtt;
 
        stat = ldns_send(&answer_pkt, (ldns_resolver *)r, query_pkt);
        if (stat != LDNS_STATUS_OK) {
@@ -1051,9 +1080,21 @@ ldns_resolver_send_pkt(ldns_pkt **answer, ldns_resolver *r,
                        if (ldns_pkt_tc(answer_pkt)) {
                                /* was EDNS0 set? */
                                if (ldns_pkt_edns_udp_size(query_pkt) == 0) {
-                                       ldns_pkt_set_edns_udp_size(query_pkt, 4096);
+                                       ldns_pkt_set_edns_udp_size(query_pkt
+                                                       , 4096);
                                        ldns_pkt_free(answer_pkt);
-                                       stat = ldns_send(&answer_pkt, r, query_pkt);
+                                       /* Nameservers should not become 
+                                        * unreachable because fragments are
+                                        * dropped (network error). We might
+                                        * still have success with TCP.
+                                        * Therefore maintain reachability
+                                        * statuses of the nameservers by
+                                        * backup and restore the rtt list.
+                                        */
+                                       rtt = ldns_resolver_backup_rtt(r);
+                                       stat = ldns_send(&answer_pkt, r
+                                                       , query_pkt);
+                                       ldns_resolver_restore_rtt(r, rtt);
                                }
                                /* either way, if it is still truncated, use TCP */
                                if (stat != LDNS_STATUS_OK ||