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diff --git a/inet/deadline.c b/inet/deadline.c
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+/* Computing deadlines for timeouts.
+ Copyright (C) 2017-2018 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
+__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
+__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
+__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;
+}