Avoid a double event_del() in evdns.c.

The bug could occur when a nameserver was marked as up, but then an
outstanding probe sent to the nameserver failed.  Now, evdns_up() cancels
any outstanding probe.

svn:r1140

diff --git a/evdns.c b/evdns.c
index 18e4b122bf048ea6ee0bf0010cc8d48654198859..791cd8bd5ad39103fee1ec9ef05a437ca869cbaa 100644 (file)
--- a/evdns.c
+++ b/evdns.c
@@ -219,6 +219,8 @@ struct nameserver {
        struct event timeout_event;  /* used to keep the timeout for */
                                     /* when we next probe this server. */
                                     /* Valid if state == 0 */
+       /* Outstanding probe request for this nameserver, if any */
+       struct evdns_request *probe_request;
        char state;  /* zero if we think that this server is down */
        char choked;  /* true if we have an EAGAIN from this server's socket */
        char write_waiting;  /* true if we are waiting for EV_WRITE events */
@@ -577,6 +579,10 @@ nameserver_up(struct nameserver *const ns) {
        log(EVDNS_LOG_WARN, "Nameserver %s is back up",
            debug_ntop((struct sockaddr *)&ns->address));
        evtimer_del(&ns->timeout_event);
+       if (ns->probe_request) {
+               evdns_cancel_request(ns->base, ns->probe_request);
+               ns->probe_request = NULL;
+       }
        ns->state = 1;
        ns->failed_times = 0;
        ns->timedout = 0;
@@ -2067,11 +2073,17 @@ nameserver_probe_callback(int result, char type, int count, int ttl, void *addre
        (void) count;
        (void) ttl;
        (void) addresses;
-
-       if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
+       ns->probe_request = NULL;
+       if (result == DNS_ERR_CANCEL) {
+               /* We canceled this request because the nameserver came up
+                * for some other reason.  Do not change our opinion about
+                * the nameserver. */
+       } else if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
                /* this is a good reply */
                nameserver_up(ns);
-       } else nameserver_probe_failed(ns);
+       } else {
+               nameserver_probe_failed(ns);
+       }
 }
 
 static void
@@ -2085,6 +2097,7 @@ nameserver_send_probe(struct nameserver *const ns) {
 
        req = request_new(ns->base, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns);
        if (!req) return;
+       ns->probe_request = req;
        /* we force this into the inflight queue no matter what */
        request_trans_id_set(req, transaction_id_pick(ns->base));
        req->ns = ns;