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   1 /*
   2  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  *
  21  */
  22
  23 #include <config.h>
  24
  25 #include "ntp.h"
  26
  27 #include "extract.h"
  28
  29 /* NTP epoch 1: January 1, 1900, 00:00:00 UTC. */
  30 #define DIFF_1970_1900 INT64_C(2208988800) /* 1970 - 1900 in seconds */
  31 /* RFC4330 - 3. NTP Timestamp Format - 6h 28m 16s UTC on 7 February 2036 */
  32 /* NTP epoch 2: February 7, 2036, 06:28:16 UTC. */
  33 #define DIFF_2036_1970 INT64_C(2085978496) /* 2036 - 1970 in seconds */
  34
  35 void
  36 p_ntp_time_fmt(netdissect_options *ndo, const char *fmt,
  37            const struct l_fixedpt *lfp)
  38 {
  39         uint32_t i;
  40         uint32_t uf;
  41         uint32_t f;
  42         double ff;
  43
  44         i = GET_BE_U_4(lfp->int_part);
  45         uf = GET_BE_U_4(lfp->fraction);
  46         ff = uf;
  47         if (ff < 0.0)           /* some compilers are buggy */
  48                 ff += FMAXINT;
  49         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
  50         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
  51         ND_PRINT("%u.%09u", i, f);
  52
  53         /*
  54          * print the UTC time in human-readable format.
  55          */
  56         if (i) {
  57             int64_t seconds_64bit;
  58             time_t seconds;
  59             char time_buf[128];
  60             const char *time_string;
  61
  62             if ((i & 0x80000000) != 0)
  63                 seconds_64bit = (int64_t)i - DIFF_1970_1900;
  64             else
  65                 seconds_64bit = (int64_t)i + DIFF_2036_1970;
  66             seconds = (time_t)seconds_64bit;
  67             if (seconds != seconds_64bit) {
  68                 /*
  69                  * It doesn't fit into a time_t, so we can't hand it
  70                  * to gmtime.
  71                  */
  72                 time_string = "[timestamp overflow]";
  73             } else {
  74                 time_string = nd_format_time(time_buf, sizeof (time_buf),
  75                                              fmt, gmtime(&seconds));
  76             }
  77             ND_PRINT(" (%s)", time_string);
  78         }
  79 }
  80
  81 void
  82 p_ntp_time(netdissect_options *ndo, const struct l_fixedpt *lfp)
  83 {
  84         /* use ISO 8601 (RFC3339) format */
  85         p_ntp_time_fmt(ndo, "%Y-%m-%dT%H:%M:%SZ", lfp);
  86 }