DNS: add ttl for negative answers using RFC 2308 idea.

diff --git a/evdns.c b/evdns.c
index 7e175edb1eed323b8d1bcf2c918407fad6251fc5..4ff9f8dccee8f2698dcdf890c42a462220a35f02 100644 (file)
--- a/evdns.c
+++ b/evdns.c
@@ -133,6 +133,7 @@
 #define TYPE_A        EVDNS_TYPE_A
 #define TYPE_CNAME     5
 #define TYPE_PTR       EVDNS_TYPE_PTR
+#define TYPE_SOA       EVDNS_TYPE_SOA
 #define TYPE_AAAA      EVDNS_TYPE_AAAA
 
 #define CLASS_INET     EVDNS_CLASS_INET
@@ -760,7 +761,7 @@ reply_run_callback(struct deferred_cb *d, void *user_pointer)
                            cb->reply.data.a.addresses,
                            user_pointer);
                else
-                       cb->user_callback(cb->err, 0, 0, 0, NULL, user_pointer);
+                       cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
                break;
        case TYPE_PTR:
                if (cb->have_reply) {
@@ -768,7 +769,7 @@ reply_run_callback(struct deferred_cb *d, void *user_pointer)
                        cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl,
                            &name, user_pointer);
                } else {
-                       cb->user_callback(cb->err, 0, 0, 0, NULL, user_pointer);
+                       cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
                }
                break;
        case TYPE_AAAA:
@@ -778,7 +779,7 @@ reply_run_callback(struct deferred_cb *d, void *user_pointer)
                            cb->reply.data.aaaa.addresses,
                            user_pointer);
                else
-                       cb->user_callback(cb->err, 0, 0, 0, NULL, user_pointer);
+                       cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
                break;
        default:
                EVUTIL_ASSERT(0);
@@ -895,7 +896,7 @@ reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply)
                }
 
                /* all else failed. Pass the failure up */
-               reply_schedule_callback(req, 0, error, NULL);
+               reply_schedule_callback(req, ttl, error, NULL);
                request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
        } else {
                /* all ok, tell the user */
@@ -998,8 +999,8 @@ reply_parse(struct evdns_base *base, u8 *packet, int length) {
 
        /* If it's not an answer, it doesn't correspond to any request. */
        if (!(flags & 0x8000)) return -1;  /* must be an answer */
-       if (flags & 0x020f) {
-               /* there was an error */
+       if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) {
+               /* there was an error and it's not NXDOMAIN */
                goto err;
        }
        /* if (!answers) return; */  /* must have an answer of some form */
@@ -1121,6 +1122,35 @@ reply_parse(struct evdns_base *base, u8 *packet, int length) {
                }
        }
 
+       if (!reply.have_answer) {
+               for (i = 0; i < authority; ++i) {
+                       u16 type, class;
+                       SKIP_NAME;
+                       GET16(type);
+                       GET16(class);
+                       GET32(ttl);
+                       GET16(datalength);
+                       if (type == TYPE_SOA && class == CLASS_INET) {
+                               u32 serial, refresh, retry, expire, minimum;
+                               SKIP_NAME;
+                               SKIP_NAME;
+                               GET32(serial);
+                               GET32(refresh);
+                               GET32(retry);
+                               GET32(expire);
+                               GET32(minimum);
+                               ttl_r = MIN(ttl_r, ttl);
+                               ttl_r = MIN(ttl_r, minimum);
+                       } else {
+                               /* skip over any other type of resource */
+                               j += datalength;
+                       }
+               }
+       }
+
+       if (ttl_r == 0xffffffff)
+               ttl_r = 0;
+
        reply_handle(req, flags, ttl_r, &reply);
        return 0;
  err: