udp: fix write_queue cleanup on sendmmsg error

This issue manifested on `connected` udp sockets trying to send
datagrams to a non-existent server and returning `ECONNREFUSED` because
an ICMP error was received before the actual sending was performed.

PR-URL: https://github.com/libuv/libuv/pull/2899
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

CMakeLists.txt

@@ -508,6 +508,7 @@ if(LIBUV_BUILD_TESTS)
        test/test-udp-send-and-recv.c
        test/test-udp-send-hang-loop.c
        test/test-udp-send-immediate.c
+       test/test-udp-sendmmsg-error.c
        test/test-udp-send-unreachable.c
        test/test-udp-try-send.c
        test/test-uname.c

Makefile.am

@@ -296,6 +296,7 @@ test_run_tests_SOURCES = test/blackhole-server.c \
                          test/test-udp-send-and-recv.c \
                          test/test-udp-send-hang-loop.c \
                          test/test-udp-send-immediate.c \
+                         test/test-udp-sendmmsg-error.c \
                          test/test-udp-send-unreachable.c \
                          test/test-udp-try-send.c \
                          test/test-uname.c \

src/unix/udp.c

@@ -367,7 +367,7 @@ write_queue_drain:
       return;
     for (i = 0, q = QUEUE_HEAD(&handle->write_queue);
          i < pkts && q != &handle->write_queue;
-         ++i, q = QUEUE_HEAD(q)) {
+         ++i, q = QUEUE_HEAD(&handle->write_queue)) {
       assert(q != NULL);
       req = QUEUE_DATA(q, uv_udp_send_t, queue);
       assert(req != NULL);

test/test-list.h

@@ -180,6 +180,7 @@ TEST_DECLARE   (udp_open_connect)
 #ifndef _WIN32
 TEST_DECLARE   (udp_send_unix)
 #endif
+TEST_DECLARE   (udp_sendmmsg_error)
 TEST_DECLARE   (udp_try_send)
 TEST_DECLARE   (pipe_bind_error_addrinuse)
 TEST_DECLARE   (pipe_bind_error_addrnotavail)
@@ -720,6 +721,7 @@ TASK_LIST_START
   TEST_ENTRY  (udp_multicast_join)
   TEST_ENTRY  (udp_multicast_join6)
   TEST_ENTRY  (udp_multicast_ttl)
+  TEST_ENTRY  (udp_sendmmsg_error)
   TEST_ENTRY  (udp_try_send)
 
   TEST_ENTRY  (udp_open)

test/test-udp-sendmmsg-error.c

@@ -0,0 +1,75 @@
+/* Copyright libuv project and contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define DATAGRAMS 6
+
+static uv_udp_t client;
+static uv_udp_send_t req[DATAGRAMS];
+
+static int send_cb_called;
+static int close_cb_called;
+
+
+static void close_cb(uv_handle_t* handle) {
+  ASSERT_PTR_EQ(handle, &client);
+  ASSERT(uv_is_closing(handle));
+  close_cb_called++;
+}
+
+
+static void send_cb(uv_udp_send_t* req, int status) {
+  if (status != 0)
+    ASSERT_EQ(status, UV_ECONNREFUSED);
+
+  if (++send_cb_called == DATAGRAMS)
+    uv_close((uv_handle_t*)&client, close_cb);
+}
+
+
+TEST_IMPL(udp_sendmmsg_error) {
+  struct sockaddr_in addr;
+  uv_buf_t buf;
+  int i;
+
+  ASSERT_EQ(0, uv_udp_init(uv_default_loop(), &client));
+  ASSERT_EQ(0, uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+  ASSERT_EQ(0, uv_udp_connect(&client, (const struct sockaddr*)&addr));
+
+  buf = uv_buf_init("TEST", 4);
+  for (i = 0; i < DATAGRAMS; ++i)
+    ASSERT_EQ(0, uv_udp_send(&req[i], &client, &buf, 1, NULL, send_cb));
+
+  uv_run(uv_default_loop(), UV_RUN_DEFAULT);
+
+  ASSERT_EQ(1, close_cb_called);
+  ASSERT_EQ(DATAGRAMS, send_cb_called);
+
+  ASSERT_EQ(0, client.send_queue_size);
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}