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/* $OpenBSD: client.c,v 1.5 2004/07/04 22:24:20 henning Exp $ */
/*
* Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
* Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
* IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "ntpd.h"
int
client_peer_init(struct ntp_peer *p)
{
struct sockaddr_in *sa_in;
struct sockaddr_in6 *sa_in6;
if ((p->query = calloc(1, sizeof(struct ntp_query))) == NULL)
fatal("client_query calloc");
switch (p->ss.ss_family) {
case AF_INET:
sa_in = (struct sockaddr_in *)&p->ss;
if (ntohs(sa_in->sin_port) == 0)
sa_in->sin_port = htons(123);
break;
case AF_INET6:
sa_in6 = (struct sockaddr_in6 *)&p->ss;
if (ntohs(sa_in6->sin6_port) == 0)
sa_in6->sin6_port = htons(123);
break;
default:
fatal("king bula sez: wrong AF in client_peer_init");
/* not reached */
}
if ((p->query->fd = socket(p->ss.ss_family, SOCK_DGRAM, 0)) == -1)
fatal("client_query socket");
p->query->msg.status = MODE_CLIENT | (NTP_VERSION << 3);
p->state = STATE_NONE;
p->next = time(NULL);
return (0);
}
int
client_query(struct ntp_peer *p)
{
/*
* Send out a random 64-bit number as our transmit time. The NTP
* server will copy said number into the originate field on the
* response that it sends us. This is totally legal per the SNTP spec.
*
* The impact of this is two fold: we no longer send out the current
* system time for the world to see (which may aid an attacker), and
* it gives us a (not very secure) way of knowing that we're not
* getting spoofed by an attacker that can't capture our traffic
* but can spoof packets from the NTP server we're communicating with.
*
* Save the real transmit timestamp locally.
*/
p->query->msg.xmttime.int_part = arc4random();
p->query->msg.xmttime.fraction = arc4random();
p->query->xmttime = gettime();
ntp_sendmsg(p->query->fd, (struct sockaddr *)&p->ss, &p->query->msg,
NTP_MSGSIZE_NOAUTH, 0);
p->state = STATE_QUERY_SENT;
p->next = 0;
p->deadline = time(NULL) + QUERYTIME_MAX;
return (0);
}
int
client_dispatch(struct ntp_peer *p)
{
struct sockaddr_storage fsa;
socklen_t fsa_len;
char buf[NTP_MSGSIZE];
ssize_t size;
struct ntp_msg msg;
double T1, T2, T3, T4;
fsa_len = sizeof(fsa);
if ((size = recvfrom(p->query->fd, &buf, sizeof(buf), 0,
(struct sockaddr *)&fsa, &fsa_len)) == -1)
fatal("recvfrom");
T4 = gettime();
ntp_getmsg(buf, size, &msg);
if (msg.orgtime.int_part != p->query->msg.xmttime.int_part ||
msg.orgtime.fraction != p->query->msg.xmttime.fraction) {
log_warn("received packet without correct cookie, discarding");
return (0);
}
/*
* From RFC 2030:
*
* Timestamp Name ID When Generated
* ------------------------------------------------------------
* Originate Timestamp T1 time request sent by client
* Receive Timestamp T2 time request received by server
* Transmit Timestamp T3 time reply sent by server
* Destination Timestamp T4 time reply received by client
*
* The roundtrip delay d and local clock offset t are defined as
*
* d = (T4 - T1) - (T2 - T3) t = ((T2 - T1) + (T3 - T4)) / 2.
*/
T1 = p->query->xmttime;
T2 = lfp_to_d(msg.rectime);
T3 = lfp_to_d(msg.xmttime);
p->offset = ((T2 - T1) + (T3 - T4)) / 2;
p->error = (T2 - T1) - (T3 - T4);
p->state = STATE_REPLY_RECEIVED;
p->next = time(NULL) + INTERVAL_QUERY;
p->deadline = 0;
log_debug("reply received: offset %f error %f", p->offset, p->error);
return (0);
}
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