aboutsummaryrefslogtreecommitdiffstats
path: root/src/ntp_server.c
blob: 3d8298f4a4a1d048a3e6e5157397019343bb0639 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
/*
 * Copyright (C) 2003-2011 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "ntp_server.h"

#include <glib.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>

#ifdef WIN32
#define WINVER 0x0501
#include <ws2tcpip.h>
#include <winsock.h>
#else
#include <sys/select.h>
#include <sys/socket.h>
#endif

/*
 * Calculate the current NTP time, store it in the buffer.
 */
static void
fill_int(unsigned char *buffer, uint32_t value)
{
	uint32_t be = GINT32_TO_BE(value);
	memcpy(buffer, &be, sizeof(be));
}

/*
 * Store time in the NTP format in the buffer
 */
static void
fill_time_buffer_with_time(unsigned char *buffer, struct timeval *tout)
{
	unsigned long secs_to_baseline = 964697997;
	double fraction;
	unsigned long long_fraction;
	unsigned long secs;

	fraction = ((double) tout->tv_usec) / 1000000.0;
	long_fraction = (unsigned long) (fraction * 256.0 * 256.0 * 256.0 * 256.0);
	secs = secs_to_baseline + tout->tv_sec;
	fill_int(buffer, secs);
	fill_int(buffer + 4, long_fraction);
}

/*
 * Calculate the current NTP time, store it in the buffer.
 */
static void
fill_time_buffer(unsigned char *buffer)
{
	struct timeval current_time;

	gettimeofday(&current_time,NULL);
	fill_time_buffer_with_time(buffer, &current_time);
}

bool
ntp_server_handle(struct ntp_server *ntp)
{
	unsigned char buf[32];
	struct sockaddr addr;
	int iter;
	unsigned int addr_len = sizeof(addr);
	int num_bytes = recvfrom(ntp->fd, buf, sizeof(buf), 0, &addr, &addr_len);
	if (num_bytes == 0) {
		return false;
	}
	fill_time_buffer(buf + 16);
	// set to response
	buf[1] = 0xd3;
	// copy request
	for (iter = 0; iter < 8; iter++) {
		buf[8 + iter] = buf[24 + iter];
	}
	fill_time_buffer(buf + 24);

	num_bytes = sendto(ntp->fd, buf, num_bytes, 0, &addr, addr_len);

	return num_bytes == sizeof(buf);
}

bool
ntp_server_check(struct ntp_server *ntp, struct timeval *tout)
{
	fd_set rdfds;
	int fdmax = 0;

	FD_ZERO(&rdfds);

	FD_SET(ntp->fd, &rdfds);
	fdmax = ntp->fd;
	select(fdmax + 1, &rdfds,NULL, NULL, tout);
	if (FD_ISSET(ntp->fd, &rdfds)) {
		if (!ntp_server_handle(ntp)) {
			g_debug("unable to send timing response\n");
			return false;
		}
	}
	return true;
}

void
ntp_server_init(struct ntp_server *ntp)
{
	ntp->port = 6002;
	ntp->fd = -1;
}

void
ntp_server_close(struct ntp_server *ntp)
{
	if (ntp->fd >= 0)
		close(ntp->fd);
}