sunrpc: Improvements for UDP client timeout handling [BZ #20257]

This commit fixes various aspects in the UDP client timeout handling.
Timeouts are now applied in a more consistent fashion.  Discarded UDP
packets no longer prevent the timeout from happening at all.

1 files changed, 122 insertions, 0 deletions

diff --git a/inet/deadline.c b/inet/deadline.c
new file mode 100644
index 0000000..c1fa415
--- /dev/null
+++ b/inet/deadline.c
@@ -0,0 +1,122 @@
+/* Computing deadlines for timeouts.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <net-internal.h>
+
+#include <assert.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <time.h>
+
+struct deadline_current_time internal_function
+__deadline_current_time (void)
+{
+  struct deadline_current_time result;
+  if (__clock_gettime (CLOCK_MONOTONIC, &result.current) != 0)
+    {
+      struct timeval current_tv;
+      if (__gettimeofday (&current_tv, NULL) == 0)
+        __libc_fatal ("Fatal error: gettimeofday system call failed\n");
+      result.current.tv_sec = current_tv.tv_sec;
+      result.current.tv_nsec = current_tv.tv_usec * 1000;
+    }
+  assert (result.current.tv_sec >= 0);
+  return result;
+}
+
+/* A special deadline value for which __deadline_is_infinite is
+   true.  */
+static inline struct deadline
+infinite_deadline (void)
+{
+  return (struct deadline) { { -1, -1 } };
+}
+
+struct deadline internal_function
+__deadline_from_timeval (struct deadline_current_time current,
+                         struct timeval tv)
+{
+  assert (__is_timeval_valid_timeout (tv));
+
+  /* Compute second-based deadline.  Perform the addition in
+     uintmax_t, which is unsigned, to simply overflow detection.  */
+  uintmax_t sec = current.current.tv_sec;
+  sec += tv.tv_sec;
+  if (sec < (uintmax_t) tv.tv_sec)
+    return infinite_deadline ();
+
+  /* Compute nanosecond deadline.  */
+  int nsec = current.current.tv_nsec + tv.tv_usec * 1000;
+  if (nsec >= 1000 * 1000 * 1000)
+    {
+      /* Carry nanosecond overflow to seconds.  */
+      nsec -= 1000 * 1000 * 1000;
+      if (sec + 1 < sec)
+        return infinite_deadline ();
+      ++sec;
+    }
+  /* This uses a GCC extension, otherwise these casts for detecting
+     overflow would not be defined.  */
+  if ((time_t) sec < 0 || sec != (uintmax_t) (time_t) sec)
+    return infinite_deadline ();
+
+  return (struct deadline) { { sec, nsec } };
+}
+
+int internal_function
+__deadline_to_ms (struct deadline_current_time current,
+                  struct deadline deadline)
+{
+  if (__deadline_is_infinite (deadline))
+    return INT_MAX;
+
+  if (current.current.tv_sec > deadline.absolute.tv_sec
+      || (current.current.tv_sec == deadline.absolute.tv_sec
+          && current.current.tv_nsec >= deadline.absolute.tv_nsec))
+    return 0;
+  time_t sec = deadline.absolute.tv_sec - current.current.tv_sec;
+  if (sec >= INT_MAX)
+    /* This value will overflow below.  */
+    return INT_MAX;
+  int nsec = deadline.absolute.tv_nsec - current.current.tv_nsec;
+  if (nsec < 0)
+    {
+      /* Borrow from the seconds field.  */
+      assert (sec > 0);
+      --sec;
+      nsec += 1000 * 1000 * 1000;
+    }
+
+  /* Prepare for rounding up to milliseconds.  */
+  nsec += 999999;
+  if (nsec > 1000 * 1000 * 1000)
+    {
+      assert (sec < INT_MAX);
+      ++sec;
+      nsec -= 1000 * 1000 * 1000;
+    }
+
+  unsigned int msec = nsec / (1000 * 1000);
+  if (sec > INT_MAX / 1000)
+    return INT_MAX;
+  msec += sec * 1000;
+  if (msec > INT_MAX)
+    return INT_MAX;
+  return msec;
+}