Fix a symptom for a bug that straycat found.

Apparently in rare cases poll() is returning POLLIN for an idle
dns worker. It reads no bytes, presumably because the idle dns
worker didn't write anything in the first place. Gosh, who knows.

Now we only trigger the assert if the idle dns worker actually
tries to send an answer to us.


svn:r2311

src/or/dns.c

@@ -568,9 +568,13 @@ int connection_dns_process_inbuf(connection_t *conn) {
     return 0;
   }
 
-  tor_assert(conn->state == DNSWORKER_STATE_BUSY);
+  if(conn->state != DNSWORKER_STATE_BUSY) {
+    log_fn(LOG_WARN,"Bug: poll() indicated than an idle dns worker was readable. Please report.");
+    return 0;
+  }
   if(buf_datalen(conn->inbuf) < 5) /* entire answer available? */
     return 0; /* not yet */
+  tor_assert(conn->state == DNSWORKER_STATE_BUSY);
   tor_assert(buf_datalen(conn->inbuf) == 5);
 
   connection_fetch_from_buf(&success,1,conn);
@@ -646,7 +650,7 @@ static int dnsworker_main(void *data) {
   for(;;) {
 
     if(recv(fd, &address_len, 1, 0) != 1) {
-      log_fn(LOG_INFO,"dnsworker exiting because tor process died.");
+      log_fn(LOG_INFO,"dnsworker exiting because tor process closed connection (either pruned idle dnsworker or died).");
       spawn_exit();
     }