The Tcpdump Group git mirrors - tcpdump/blob - ntp.c

   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 #define JAN_1970        INT64_T_CONSTANT(2208988800)    /* 1970 - 1900 in seconds */
  30
  31 void
  32 p_ntp_time(netdissect_options *ndo,
  33            const struct l_fixedpt *lfp)
  34 {
  35         uint32_t i;
  36         uint32_t uf;
  37         uint32_t f;
  38         double ff;
  39
  40         i = GET_BE_U_4(lfp->int_part);
  41         uf = GET_BE_U_4(lfp->fraction);
  42         ff = uf;
  43         if (ff < 0.0)           /* some compilers are buggy */
  44                 ff += FMAXINT;
  45         ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
  46         f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
  47         ND_PRINT("%u.%09u", i, f);
  48
  49         /*
  50          * print the UTC time in human-readable format.
  51          */
  52         if (i) {
  53             int64_t seconds_64bit = (int64_t)i - JAN_1970;
  54             time_t seconds;
  55             char time_buf[128];
  56             const char *time_string;
  57
  58             seconds = (time_t)seconds_64bit;
  59             if (seconds != seconds_64bit) {
  60                 /*
  61                  * It doesn't fit into a time_t, so we can't hand it
  62                  * to gmtime.
  63                  */
  64                 time_string = "[Time is too large to fit into a time_t]";
  65             } else {
  66                 /* use ISO 8601 (RFC3339) format */
  67                 time_string = nd_format_time(time_buf, sizeof (time_buf),
  68                   "%Y-%m-%dT%H:%M:%SZ", gmtime(&seconds));
  69             }
  70             ND_PRINT(" (%s)", time_string);
  71         }
  72 }