url: Add option CURLOPT_RESOLVER_START_FUNCTION

- Add new option CURLOPT_RESOLVER_START_FUNCTION to set a callback that
  will be called every time before a new resolve request is started
  (ie before a host is resolved) with a pointer to backend-specific
  resolver data. Currently this is only useful for ares.

- Add new option CURLOPT_RESOLVER_START_DATA to set a user pointer to
  pass to the resolver start callback.

Closes https://github.com/curl/curl/pull/2311

5 files changed, 168 insertions, 2 deletions

diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc
index 892012988..55abec873 100644
--- a/tests/data/Makefile.inc
+++ b/tests/data/Makefile.inc
@@ -80,7 +80,7 @@ test617 test618 test619 test620 test621 test622 test623 test624 test625 \
 test626 test627 test628 test629 test630 test631 test632 test633 test634 \
 test635 test636 test637 test638 test639 test640 test641 test642 \
 test643 test644 test645 test646 test647 test648 test649 test650 test651 \
-test652 test653 test654 \
+test652 test653 test654 test655 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
 test709 test710 test711 test712 test713 test714 test715 \
diff --git a/tests/data/test655 b/tests/data/test655
new file mode 100644
index 000000000..d98729c08
--- /dev/null
+++ b/tests/data/test655
@@ -0,0 +1,50 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK

+Date: Thu, 09 Nov 2010 14:49:00 GMT

+Server: test-server/fake swsclose

+Connection: close

+Content-Type: text/html

+

+hello
+</data>
+<datacheck>
+hello
+</datacheck>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+# tool is what to use instead of 'curl'
+<tool>
+lib655
+</tool>
+
+ <name>
+resolver start callback
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/655
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+0
+</errorcode>
+</verify>
+</testcase>
diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index c47659804..e7e8c486a 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -20,7 +20,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib559 lib560 lib562 lib564 lib565 lib566 lib567 lib568 lib569 lib570   \
  lib571 lib572 lib573 lib574 lib575 lib576        lib578 lib579 lib582   \
  lib583 lib585 lib586 lib587 lib589 lib590 lib591 lib597 lib598 lib599   \
- lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 \
+ lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 lib655 \
  lib1500 lib1501 lib1502 lib1503 lib1504 lib1505 lib1506 lib1507 lib1508 \
  lib1509 lib1510 lib1511 lib1512 lib1513 lib1514 lib1515         lib1517 \
  lib1520 lib1521 \
@@ -327,6 +327,9 @@ lib653_CPPFLAGS = $(AM_CPPFLAGS)
 lib654_SOURCES = lib654.c $(SUPPORTFILES)
 lib654_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib655_SOURCES = lib655.c $(SUPPORTFILES)
+lib655_CPPFLAGS = $(AM_CPPFLAGS)
+
 lib1500_SOURCES = lib1500.c $(SUPPORTFILES) $(TESTUTIL)
 lib1500_LDADD = $(TESTUTIL_LIBS)
 lib1500_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib655.c b/tests/libtest/lib655.c
new file mode 100644
index 000000000..7ee12a3f7
--- /dev/null
+++ b/tests/libtest/lib655.c
@@ -0,0 +1,112 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "test.h"
+
+#include "memdebug.h"
+
+const char TEST_DATA_STRING[] = "Test data";
+static int cb_count = 0;
+
+static int
+resolver_alloc_cb_fail(void *resolver_state, void *reserved, void *userdata)
+{
+  (void)resolver_state;
+  (void)reserved;
+
+  cb_count++;
+  if(strcmp(userdata, TEST_DATA_STRING)) {
+    fprintf(stderr, "Invalid test data received");
+    exit(1);
+  }
+
+  return 1;
+}
+
+static int
+resolver_alloc_cb_pass(void *resolver_state, void *reserved, void *userdata)
+{
+  (void)resolver_state;
+  (void)reserved;
+
+  cb_count++;
+  if(strcmp(userdata, TEST_DATA_STRING)) {
+    fprintf(stderr, "Invalid test data received");
+    exit(1);
+  }
+
+  return 0;
+}
+
+int test(char *URL)
+{
+  CURL *curl;
+  CURLcode res = CURLE_OK;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+  curl = curl_easy_init();
+  if(!curl) {
+    fprintf(stderr, "curl_easy_init() failed\n");
+    res = TEST_ERR_MAJOR_BAD;
+    goto test_cleanup;
+  }
+
+  /* First set the URL that is about to receive our request. */
+  test_setopt(curl, CURLOPT_URL, URL);
+
+  test_setopt(curl, CURLOPT_RESOLVER_START_DATA, TEST_DATA_STRING);
+  test_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, resolver_alloc_cb_fail);
+
+  /* this should fail */
+  res = curl_easy_perform(curl);
+  if(res != CURLE_COULDNT_RESOLVE_HOST) {
+    fprintf(stderr, "curl_easy_perform should have returned "
+            "CURLE_COULDNT_RESOLVE_HOST but instead returned error %d\n", res);
+    if(res == CURLE_OK)
+      res = TEST_ERR_FAILURE;
+    goto test_cleanup;
+  }
+
+  test_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, resolver_alloc_cb_pass);
+
+  /* this should succeed */
+  res = curl_easy_perform(curl);
+  if(res) {
+    fprintf(stderr, "curl_easy_perform failed.\n");
+    goto test_cleanup;
+  }
+
+  if(cb_count != 2) {
+    fprintf(stderr, "Unexpected number of callbacks: %d\n", cb_count);
+    res = TEST_ERR_FAILURE;
+    goto test_cleanup;
+  }
+
+test_cleanup:
+  /* always cleanup */
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return (int)res;
+}
diff --git a/tests/libtest/mk-lib1521.pl b/tests/libtest/mk-lib1521.pl
index 6ded47220..fbb1cdee2 100755
--- a/tests/libtest/mk-lib1521.pl
+++ b/tests/libtest/mk-lib1521.pl
@@ -132,6 +132,7 @@ static curl_chunk_end_callback chunk_end_cb;
 static curl_fnmatch_callback fnmatch_cb;
 static curl_closesocket_callback closesocketcb;
 static curl_xferinfo_callback xferinfocb;
+static curl_resolver_start_callback resolver_start_cb;
 
 int test(char *URL)
 {