progress: prevent resetting t_starttransfer

Prevent `Curl_pgrsTime` from modifying `t_starttransfer` when invoked
with `TIMER_STARTTRANSFER` more than once during a single request.

When a redirect occurs, this is considered a new request and
`t_starttransfer` can be updated to reflect the `t_starttransfer` time
of the redirect request.

Closes #1616

Bug: https://github.com/curl/curl/pull/1602#issuecomment-310267370

2 files changed, 100 insertions, 0 deletions

diff --git a/tests/unit/Makefile.inc b/tests/unit/Makefile.inc
index ee01627df..1320b4a67 100644
--- a/tests/unit/Makefile.inc
+++ b/tests/unit/Makefile.inc
@@ -7,6 +7,7 @@ UNITFILES = curlcheck.h \
 # These are all unit test programs
 UNITPROGS = unit1300 unit1301 unit1302 unit1303 unit1304 unit1305 unit1307	\
  unit1308 unit1309 unit1330 unit1394 unit1395 unit1396 unit1397 unit1398	\
+ unit1399	\
  unit1600 unit1601 unit1602 unit1603 unit1604 unit1605 unit1606
 
 unit1300_SOURCES = unit1300.c $(UNITFILES)
@@ -57,6 +58,9 @@ unit1397_CPPFLAGS = $(AM_CPPFLAGS)
 unit1398_SOURCES = unit1398.c $(UNITFILES)
 unit1398_CPPFLAGS = $(AM_CPPFLAGS)
 
+unit1399_SOURCES = unit1399.c $(UNITFILES)
+unit1399_CPPFLAGS = $(AM_CPPFLAGS)
+
 unit1600_SOURCES = unit1600.c $(UNITFILES)
 unit1600_CPPFLAGS = $(AM_CPPFLAGS)
 
diff --git a/tests/unit/unit1399.c b/tests/unit/unit1399.c
new file mode 100644
index 000000000..1befc8aaf
--- /dev/null
+++ b/tests/unit/unit1399.c
@@ -0,0 +1,96 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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 "curlcheck.h"
+
+#include "urldata.h"
+#include "progress.h"
+
+static int usec_magnitude = 1000000;
+
+static bool unit_setup(void)
+{
+  return CURLE_OK;
+}
+
+static void unit_stop(void)
+{
+
+}
+
+static bool usec_matches_seconds(time_t time_usec, int expected_seconds)
+{
+  int time_sec = (int)(time_usec / usec_magnitude);
+  return time_sec == expected_seconds;
+}
+
+UNITTEST_START
+  struct Curl_easy data;
+  struct timeval now = Curl_tvnow();
+
+  data.progress.t_starttransfer = 0;
+  data.progress.t_redirect = 0;
+
+  /*
+  * Set the startsingle time to a second ago. This time is used by
+  * Curl_pgrsTime to calculate how much time the events takes.
+  * t_starttransfer should be updated to reflect the difference from this time
+  * when `Curl_pgrsTime is invoked.
+  */
+  data.progress.t_startsingle.tv_sec = now.tv_sec - 1;
+  data.progress.t_startsingle.tv_usec = now.tv_usec;
+
+  Curl_pgrsTime(&data, TIMER_STARTTRANSFER);
+
+  fail_unless(usec_matches_seconds(data.progress.t_starttransfer, 1),
+              "about 1 second should have passed");
+
+  /*
+  * Update the startsingle time to a second ago to simulate another second has
+  * passed.
+  * Now t_starttransfer should not be changed, as t_starttransfer has already
+  * occurred and another invocation of `Curl_pgrsTime` for TIMER_STARTTRANSFER
+  * is superfluous.
+  */
+  data.progress.t_startsingle.tv_sec = now.tv_sec - 2;
+  data.progress.t_startsingle.tv_usec = now.tv_usec;
+
+  Curl_pgrsTime(&data, TIMER_STARTTRANSFER);
+
+  fail_unless(usec_matches_seconds(data.progress.t_starttransfer, 1),
+              "about 1 second should have passed");
+
+  /*
+  * Simulate what happens after a redirect has occurred.
+  *
+  * Since the value of t_starttransfer is set to the value from the first
+  * request, it should be updated when a transfer occurs such that
+  * t_starttransfer is the starttransfer time of the redirect request.
+  */
+  data.progress.t_startsingle.tv_sec = now.tv_sec - 3;
+  data.progress.t_startsingle.tv_usec = now.tv_usec;
+  data.progress.t_redirect = (now.tv_sec - 2) * usec_magnitude;
+
+  Curl_pgrsTime(&data, TIMER_STARTTRANSFER);
+
+  fail_unless(usec_matches_seconds(data.progress.t_starttransfer, 3),
+              "about 3 second should have passed");
+UNITTEST_STOP