xref: /aosp_15_r20/external/tcpdump/ntp.c (revision 05b00f6010a2396e3db2409989fc67270046269f)
1*05b00f60SXin Li /*
2*05b00f60SXin Li  * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
3*05b00f60SXin Li  *	The Regents of the University of California.  All rights reserved.
4*05b00f60SXin Li  *
5*05b00f60SXin Li  * Redistribution and use in source and binary forms, with or without
6*05b00f60SXin Li  * modification, are permitted provided that: (1) source code distributions
7*05b00f60SXin Li  * retain the above copyright notice and this paragraph in its entirety, (2)
8*05b00f60SXin Li  * distributions including binary code include the above copyright notice and
9*05b00f60SXin Li  * this paragraph in its entirety in the documentation or other materials
10*05b00f60SXin Li  * provided with the distribution, and (3) all advertising materials mentioning
11*05b00f60SXin Li  * features or use of this software display the following acknowledgement:
12*05b00f60SXin Li  * ``This product includes software developed by the University of California,
13*05b00f60SXin Li  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14*05b00f60SXin Li  * the University nor the names of its contributors may be used to endorse
15*05b00f60SXin Li  * or promote products derived from this software without specific prior
16*05b00f60SXin Li  * written permission.
17*05b00f60SXin Li  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18*05b00f60SXin Li  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19*05b00f60SXin Li  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20*05b00f60SXin Li  *
21*05b00f60SXin Li  */
22*05b00f60SXin Li 
23*05b00f60SXin Li #ifdef HAVE_CONFIG_H
24*05b00f60SXin Li #include <config.h>
25*05b00f60SXin Li #endif
26*05b00f60SXin Li 
27*05b00f60SXin Li #include "ntp.h"
28*05b00f60SXin Li 
29*05b00f60SXin Li #include "extract.h"
30*05b00f60SXin Li 
31*05b00f60SXin Li #define	JAN_1970	INT64_T_CONSTANT(2208988800)	/* 1970 - 1900 in seconds */
32*05b00f60SXin Li 
33*05b00f60SXin Li void
p_ntp_time(netdissect_options * ndo,const struct l_fixedpt * lfp)34*05b00f60SXin Li p_ntp_time(netdissect_options *ndo,
35*05b00f60SXin Li 	   const struct l_fixedpt *lfp)
36*05b00f60SXin Li {
37*05b00f60SXin Li 	uint32_t i;
38*05b00f60SXin Li 	uint32_t uf;
39*05b00f60SXin Li 	uint32_t f;
40*05b00f60SXin Li 	double ff;
41*05b00f60SXin Li 
42*05b00f60SXin Li 	i = GET_BE_U_4(lfp->int_part);
43*05b00f60SXin Li 	uf = GET_BE_U_4(lfp->fraction);
44*05b00f60SXin Li 	ff = uf;
45*05b00f60SXin Li 	if (ff < 0.0)		/* some compilers are buggy */
46*05b00f60SXin Li 		ff += FMAXINT;
47*05b00f60SXin Li 	ff = ff / FMAXINT;			/* shift radix point by 32 bits */
48*05b00f60SXin Li 	f = (uint32_t)(ff * 1000000000.0);	/* treat fraction as parts per billion */
49*05b00f60SXin Li 	ND_PRINT("%u.%09u", i, f);
50*05b00f60SXin Li 
51*05b00f60SXin Li 	/*
52*05b00f60SXin Li 	 * print the UTC time in human-readable format.
53*05b00f60SXin Li 	 */
54*05b00f60SXin Li 	if (i) {
55*05b00f60SXin Li 	    int64_t seconds_64bit = (int64_t)i - JAN_1970;
56*05b00f60SXin Li 	    time_t seconds;
57*05b00f60SXin Li 	    char time_buf[128];
58*05b00f60SXin Li 	    const char *time_string;
59*05b00f60SXin Li 
60*05b00f60SXin Li 	    seconds = (time_t)seconds_64bit;
61*05b00f60SXin Li 	    if (seconds != seconds_64bit) {
62*05b00f60SXin Li 		/*
63*05b00f60SXin Li 		 * It doesn't fit into a time_t, so we can't hand it
64*05b00f60SXin Li 		 * to gmtime.
65*05b00f60SXin Li 		 */
66*05b00f60SXin Li 		time_string = "[Time is too large to fit into a time_t]";
67*05b00f60SXin Li 	    } else {
68*05b00f60SXin Li 		/* use ISO 8601 (RFC3339) format */
69*05b00f60SXin Li 		time_string = nd_format_time(time_buf, sizeof (time_buf),
70*05b00f60SXin Li 		  "%Y-%m-%dT%H:%M:%SZ", gmtime(&seconds));
71*05b00f60SXin Li 	    }
72*05b00f60SXin Li 	    ND_PRINT(" (%s)", time_string);
73*05b00f60SXin Li 	}
74*05b00f60SXin Li }
75