2874. [bug] Cache lack of EDNS support only after the server

                        successfully responds to the query using plain DNS.
                        [RT #20930]

diff --git a/CHANGES b/CHANGES
index cce109dae0bfc184df1abc44d468c7332ed6ce4a..6c7e2f8437b73bbeedfa3b16a6f91747d02ceee4 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+2874.  [bug]           Cache lack of EDNS support only after the server
+                       successfully responds to the query using plain DNS.
+                       [RT #20930]
+
 2873.  [bug]           Canceling a dynamic update via the dns/client module
                        could trigger an assertion failure. [RT #21133]
 

diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index 12f89e68f3e833cc35f5179163c5a418e50c602d..8d4b5ed586ca859f2b614a76c5db1c0639ad7209 100644 (file)
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: resolver.c,v 1.419 2010/03/04 22:25:31 marka Exp $ */
+/* $Id: resolver.c,v 1.420 2010/04/20 07:28:52 marka Exp $ */
 
 /*! \file */
 
@@ -203,6 +203,7 @@ struct fetchctx {
        isc_sockaddrlist_t              bad;
        isc_sockaddrlist_t              edns;
        isc_sockaddrlist_t              edns512;
+       isc_sockaddrlist_t              bad_edns;
        dns_validator_t                 *validator;
        ISC_LIST(dns_validator_t)       validators;
        dns_db_t *                      cache;
@@ -1561,6 +1562,36 @@ fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
        return (result);
 }
 
+static isc_boolean_t
+bad_edns(fetchctx_t *fctx, isc_sockaddr_t *address) {
+       isc_sockaddr_t *sa;
+
+       for (sa = ISC_LIST_HEAD(fctx->bad_edns);
+            sa != NULL;
+            sa = ISC_LIST_NEXT(sa, link)) {
+               if (isc_sockaddr_equal(sa, address))
+                       return (ISC_TRUE);
+       }
+
+       return (ISC_FALSE);
+}
+
+static void
+add_bad_edns(fetchctx_t *fctx, isc_sockaddr_t *address) {
+       isc_sockaddr_t *sa;
+
+       if (bad_edns(fctx, address))
+               return;
+
+       sa = isc_mem_get(fctx->res->buckets[fctx->bucketnum].mctx,
+                        sizeof(*sa));
+       if (sa == NULL)
+               return;
+
+       *sa = *address;
+       ISC_LIST_INITANDAPPEND(fctx->bad_edns, sa, link);
+}
+
 static isc_boolean_t
 triededns(fetchctx_t *fctx, isc_sockaddr_t *address) {
        isc_sockaddr_t *sa;
@@ -3129,6 +3160,14 @@ fctx_destroy(fetchctx_t *fctx) {
                isc_mem_put(res->buckets[bucketnum].mctx, sa, sizeof(*sa));
        }
 
+       for (sa = ISC_LIST_HEAD(fctx->bad_edns);
+            sa != NULL;
+            sa = next_sa) {
+               next_sa = ISC_LIST_NEXT(sa, link);
+               ISC_LIST_UNLINK(fctx->bad_edns, sa, link);
+               isc_mem_put(res->buckets[bucketnum].mctx, sa, sizeof(*sa));
+       }
+
        isc_timer_detach(&fctx->timer);
        dns_message_destroy(&fctx->rmessage);
        dns_message_destroy(&fctx->qmessage);
@@ -3500,6 +3539,7 @@ fctx_create(dns_resolver_t *res, dns_name_t *name, dns_rdatatype_t type,
        ISC_LIST_INIT(fctx->bad);
        ISC_LIST_INIT(fctx->edns);
        ISC_LIST_INIT(fctx->edns512);
+       ISC_LIST_INIT(fctx->bad_edns);
        ISC_LIST_INIT(fctx->validators);
        fctx->validator = NULL;
        fctx->find = NULL;
@@ -6620,7 +6660,26 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
         * ensured by the dispatch code).
         */
 
-
+       /*
+        * We have an affirmative response to the query and we have
+        * previously got a response from this server which indicated
+        * EDNS may not be supported so we can now cache the lack of
+        * EDNS support.
+        */
+       if (opt == NULL &&
+           (message->rcode == dns_rcode_noerror ||
+            message->rcode == dns_rcode_nxdomain ||
+            message->rcode == dns_rcode_refused ||
+            message->rcode == dns_rcode_yxdomain) &&
+            bad_edns(fctx, &query->addrinfo->sockaddr)) {
+               char addrbuf[ISC_SOCKADDR_FORMATSIZE];
+               isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
+                                   sizeof(addrbuf));
+               dns_adb_changeflags(fctx->adb, query->addrinfo,
+                                   DNS_FETCHOPT_NOEDNS0,
+                                   DNS_FETCHOPT_NOEDNS0);
+       }
+               
        /*
         * Deal with truncated responses by retrying using TCP.
         */
@@ -6675,9 +6734,9 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
        if (message->rcode != dns_rcode_noerror &&
            message->rcode != dns_rcode_nxdomain) {
                if (((message->rcode == dns_rcode_formerr ||
-                    message->rcode == dns_rcode_notimp) ||
-                   (message->rcode == dns_rcode_servfail &&
-                    dns_message_getopt(message) == NULL)) &&
+                     message->rcode == dns_rcode_notimp) ||
+                    (message->rcode == dns_rcode_servfail &&
+                     dns_message_getopt(message) == NULL)) &&
                    (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                        /*
                         * It's very likely they don't like EDNS0.
@@ -6693,12 +6752,9 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
                        options |= DNS_FETCHOPT_NOEDNS0;
                        resend = ISC_TRUE;
                        /*
-                        * Remember that they don't like EDNS0.
+                        * Remember that they may not like EDNS0.
                         */
-                       if (message->rcode != dns_rcode_servfail)
-                               dns_adb_changeflags(fctx->adb, query->addrinfo,
-                                                   DNS_FETCHOPT_NOEDNS0,
-                                                   DNS_FETCHOPT_NOEDNS0);
+                       add_bad_edns(fctx, &query->addrinfo->sockaddr);
                        inc_stats(fctx->res, dns_resstatscounter_edns0fail);
                } else if (message->rcode == dns_rcode_formerr) {
                        if (ISFORWARDER(query->addrinfo)) {