http: allow overriding timecond with custom header

With CURLOPT_TIMECONDITION set, a header is automatically added (e.g.
If-Modified-Since).  Allow this to be replaced or suppressed with
CURLOPT_HTTPHEADER.

Fixes #4103
Closes #4109

2 files changed, 83 insertions, 1 deletions

diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 0eb99a1d8..f5effd97d 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -32,7 +32,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib1540 lib1541 \
  lib1550 lib1551 lib1552 lib1553 lib1554 lib1555 lib1556 lib1557 \
  lib1558 lib1559 lib1560 \
- lib1591 lib1592 \
+ lib1591 lib1592 lib1593 \
  lib1900 lib1905 lib1906 \
  lib2033
 
@@ -541,6 +541,9 @@ lib1592_SOURCES = lib1592.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1592_LDADD = $(TESTUTIL_LIBS)
 lib1592_CPPFLAGS = $(AM_CPPFLAGS) -DLIB1592
 
+lib1593_SOURCES = lib1593.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib1593_LDADD = $(TESTUTIL_LIBS)
+
 lib1900_SOURCES = lib1900.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1900_LDADD = $(TESTUTIL_LIBS)
 lib1900_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib1593.c b/tests/libtest/lib1593.c
new file mode 100644
index 000000000..5408c724a
--- /dev/null
+++ b/tests/libtest/lib1593.c
@@ -0,0 +1,79 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, 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.
+ *
+ ***************************************************************************/
+
+/* Test suppressing the If-Modified-Since header */
+
+#include "test.h"
+
+#include "memdebug.h"
+
+int test(char *URL)
+{
+  struct curl_slist *header = NULL;
+  long unmet;
+  CURL *curl = NULL;
+  int res = 0;
+
+  global_init(CURL_GLOBAL_ALL);
+
+  easy_init(curl);
+
+  easy_setopt(curl, CURLOPT_URL, URL);
+  easy_setopt(curl, CURLOPT_TIMECONDITION, (long)CURL_TIMECOND_IFMODSINCE);
+  /* Some TIMEVALUE; it doesn't matter. */
+  easy_setopt(curl, CURLOPT_TIMEVALUE, 1566210680L);
+
+  header = curl_slist_append(NULL, "If-Modified-Since:");
+  if(!header) {
+    res = TEST_ERR_MAJOR_BAD;
+    goto test_cleanup;
+  }
+
+  easy_setopt(curl, CURLOPT_HTTPHEADER, header);
+
+  res = curl_easy_perform(curl);
+  if(res)
+    goto test_cleanup;
+
+  /* Confirm that the condition checking still worked, even though we
+   * suppressed the actual header.
+   * The server returns 304, which means the condition is "unmet".
+   */
+
+  res = curl_easy_getinfo(curl, CURLINFO_CONDITION_UNMET, &unmet);
+  if(res)
+    goto test_cleanup;
+
+  if(unmet != 1L) {
+    res = TEST_ERR_FAILURE;
+    goto test_cleanup;
+  }
+
+test_cleanup:
+
+  /* always cleanup */
+  curl_easy_cleanup(curl);
+  curl_slist_free_all(header);
+  curl_global_cleanup();
+
+  return res;
+}