asyn-thread: create a socketpair to wait on

Closes #4157

lib/asyn-thread.c

@@ -163,6 +163,9 @@ struct thread_sync_data {
   char *hostname;        /* hostname to resolve, Curl_async.hostname
                             duplicate */
   int port;
+#ifdef HAVE_SOCKETPAIR
+  curl_socket_t sock_pair[2]; /* socket pair */
+#endif
   int sock_error;
   Curl_addrinfo *res;
 #ifdef HAVE_GETADDRINFO
@@ -197,6 +200,16 @@ void destroy_thread_sync_data(struct thread_sync_data * tsd)
   if(tsd->res)
     Curl_freeaddrinfo(tsd->res);
 
+#ifdef HAVE_SOCKETPAIR
+  /* close socket pair */
+  if(tsd->sock_pair[0] != CURL_SOCKET_BAD) {
+    sclose(tsd->sock_pair[0]);
+  }
+
+  if(tsd->sock_pair[1] != CURL_SOCKET_BAD) {
+    sclose(tsd->sock_pair[1]);
+  }
+#endif
   memset(tsd, 0, sizeof(*tsd));
 }
 
@@ -230,6 +243,14 @@ int init_thread_sync_data(struct thread_data * td,
 
   Curl_mutex_init(tsd->mtx);
 
+#ifdef HAVE_SOCKETPAIR
+  /* create socket pair */
+  if(socketpair(AF_LOCAL, SOCK_STREAM, 0, &tsd->sock_pair[0]) < 0) {
+    tsd->sock_pair[0] = CURL_SOCKET_BAD;
+    tsd->sock_pair[1] = CURL_SOCKET_BAD;
+    goto err_exit;
+  }
+#endif
   tsd->sock_error = CURL_ASYNC_SUCCESS;
 
   /* Copying hostname string because original can be destroyed by parent
@@ -276,6 +297,9 @@ static unsigned int CURL_STDCALL getaddrinfo_thread(void *arg)
   struct thread_data *td = tsd->td;
   char service[12];
   int rc;
+#ifdef HAVE_SOCKETPAIR
+  char buf[1];
+#endif
 
   msnprintf(service, sizeof(service), "%d", tsd->port);
 
@@ -298,6 +322,16 @@ static unsigned int CURL_STDCALL getaddrinfo_thread(void *arg)
     free(td);
   }
   else {
+#ifdef HAVE_SOCKETPAIR
+    if(tsd->sock_pair[1] != CURL_SOCKET_BAD) {
+      /* DNS has been resolved, signal client task */
+      buf[0] = 1;
+      if(write(tsd->sock_pair[1],  buf, sizeof(buf)) < 0) {
+        /* update sock_erro to errno */
+        tsd->sock_error = SOCKERRNO;
+      }
+    }
+#endif
     tsd->done = 1;
     Curl_mutex_release(tsd->mtx);
   }
@@ -595,12 +629,27 @@ int Curl_resolver_getsock(struct connectdata *conn,
                           curl_socket_t *socks,
                           int numsocks)
 {
+  int ret_val = 0;
   time_t milli;
   timediff_t ms;
   struct Curl_easy *data = conn->data;
   struct resdata *reslv = (struct resdata *)data->state.resolver;
+#ifdef HAVE_SOCKETPAIR
+  struct thread_data *td = (struct thread_data*)conn->async.os_specific;
+  int loop_idx;
+#else
   (void)socks;
   (void)numsocks;
+#endif
+
+#ifdef HAVE_SOCKETPAIR
+  if(td) {
+    /* return read fd to client for polling the DNS resolution status */
+    socks[0] = td->tsd.sock_pair[0];
+    ret_val = GETSOCK_READSOCK(0);
+  }
+  else {
+#endif
     ms = Curl_timediff(Curl_now(), reslv->start);
     if(ms < 3)
       milli = 0;
@@ -611,7 +660,12 @@ int Curl_resolver_getsock(struct connectdata *conn,
     else
       milli = 200;
     Curl_expire(data, milli, EXPIRE_ASYNC_NAME);
-  return 0;
+#ifdef HAVE_SOCKETPAIR
+  }
+#endif
+
+
+  return ret_val;
 }
 
 #ifndef HAVE_GETADDRINFO