/*****************************************************************************
*
* Monitoring check_ntp_time plugin
*
* License: GPL
* Copyright (c) 2006 Sean Finney <seanius@seanius.net>
* Copyright (c) 2006-2024 Monitoring Plugins Development Team
*
* Description:
*
* This file contains the check_ntp_time plugin
*
* This plugin checks the clock offset between the local host and a
* remote NTP server. It is independent of any commandline programs or
* external libraries.
*
* If you'd rather want to monitor an NTP server, please use
* check_ntp_peer.
*
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*
*
*****************************************************************************/
const char *progname = "check_ntp_time";
const char *copyright = "2006-2024";
const char *email = "devel@monitoring-plugins.org";
#include "common.h"
#include "netutils.h"
#include "utils.h"
static char *server_address = NULL;
static char *port = "123";
static int verbose = 0;
static bool quiet = false;
static char *owarn = "60";
static char *ocrit = "120";
static int time_offset = 0;
static int process_arguments(int, char **);
static thresholds *offset_thresholds = NULL;
static void print_help(void);
void print_usage(void);
/* number of times to perform each request to get a good average. */
#ifndef AVG_NUM
# define AVG_NUM 4
#endif
/* max size of control message data */
#define MAX_CM_SIZE 468
/* this structure holds everything in an ntp request/response as per rfc1305 */
typedef struct {
uint8_t flags; /* byte with leapindicator,vers,mode. see macros */
uint8_t stratum; /* clock stratum */
int8_t poll; /* polling interval */
int8_t precision; /* precision of the local clock */
int32_t rtdelay; /* total rt delay, as a fixed point num. see macros */
uint32_t rtdisp; /* like above, but for max err to primary src */
uint32_t refid; /* ref clock identifier */
uint64_t refts; /* reference timestamp. local time local clock */
uint64_t origts; /* time at which request departed client */
uint64_t rxts; /* time at which request arrived at server */
uint64_t txts; /* time at which request departed server */
} ntp_message;
/* this structure holds data about results from querying offset from a peer */
typedef struct {
time_t waiting; /* ts set when we started waiting for a response */
int num_responses; /* number of successfully received responses */
uint8_t stratum; /* copied verbatim from the ntp_message */
double rtdelay; /* converted from the ntp_message */
double rtdisp; /* converted from the ntp_message */
double offset[AVG_NUM]; /* offsets from each response */
uint8_t flags; /* byte with leapindicator,vers,mode. see macros */
} ntp_server_results;
/* bits 1,2 are the leap indicator */
#define LI_MASK 0xc0
#define LI(x) ((x & LI_MASK) >> 6)
#define LI_SET(x, y) \
do { \
x |= ((y << 6) & LI_MASK); \
} while (0)
/* and these are the values of the leap indicator */
#define LI_NOWARNING 0x00
#define LI_EXTRASEC 0x01
#define LI_MISSINGSEC 0x02
#define LI_ALARM 0x03
/* bits 3,4,5 are the ntp version */
#define VN_MASK 0x38
#define VN(x) ((x & VN_MASK) >> 3)
#define VN_SET(x, y) \
do { \
x |= ((y << 3) & VN_MASK); \
} while (0)
#define VN_RESERVED 0x02
/* bits 6,7,8 are the ntp mode */
#define MODE_MASK 0x07
#define MODE(x) (x & MODE_MASK)
#define MODE_SET(x, y) \
do { \
x |= (y & MODE_MASK); \
} while (0)
/* here are some values */
#define MODE_CLIENT 0x03
#define MODE_CONTROLMSG 0x06
/* In control message, bits 8-10 are R,E,M bits */
#define REM_MASK 0xe0
#define REM_RESP 0x80
#define REM_ERROR 0x40
#define REM_MORE 0x20
/* In control message, bits 11 - 15 are opcode */
#define OP_MASK 0x1f
#define OP_SET(x, y) \
do { \
x |= (y & OP_MASK); \
} while (0)
#define OP_READSTAT 0x01
#define OP_READVAR 0x02
/* In peer status bytes, bits 6,7,8 determine clock selection status */
#define PEER_SEL(x) ((ntohs(x) >> 8) & 0x07)
#define PEER_INCLUDED 0x04
#define PEER_SYNCSOURCE 0x06
/**
** a note about the 32-bit "fixed point" numbers:
**
they are divided into halves, each being a 16-bit int in network byte order:
- the first 16 bits are an int on the left side of a decimal point.
- the second 16 bits represent a fraction n/(2^16)
likewise for the 64-bit "fixed point" numbers with everything doubled :)
**/
/* macros to access the left/right 16 bits of a 32-bit ntp "fixed point"
number. note that these can be used as lvalues too */
#define L16(x) (((uint16_t *)&x)[0])
#define R16(x) (((uint16_t *)&x)[1])
/* macros to access the left/right 32 bits of a 64-bit ntp "fixed point"
number. these too can be used as lvalues */
#define L32(x) (((uint32_t *)&x)[0])
#define R32(x) (((uint32_t *)&x)[1])
/* ntp wants seconds since 1/1/00, epoch is 1/1/70. this is the difference */
#define EPOCHDIFF 0x83aa7e80UL
/* extract a 32-bit ntp fixed point number into a double */
#define NTP32asDOUBLE(x) (ntohs(L16(x)) + (double)ntohs(R16(x)) / 65536.0)
/* likewise for a 64-bit ntp fp number */
#define NTP64asDOUBLE(n) \
(double)(((uint64_t)n) ? (ntohl(L32(n)) - EPOCHDIFF) + (.00000001 * (0.5 + (double)(ntohl(R32(n)) / 42.94967296))) : 0)
/* convert a struct timeval to a double */
#define TVasDOUBLE(x) (double)(x.tv_sec + (0.000001 * x.tv_usec))
/* convert an ntp 64-bit fp number to a struct timeval */
#define NTP64toTV(n, t) \
do { \
if (!n) \
t.tv_sec = t.tv_usec = 0; \
else { \
t.tv_sec = ntohl(L32(n)) - EPOCHDIFF; \
t.tv_usec = (int)(0.5 + (double)(ntohl(R32(n)) / 4294.967296)); \
} \
} while (0)
/* convert a struct timeval to an ntp 64-bit fp number */
#define TVtoNTP64(t, n) \
do { \
if (!t.tv_usec && !t.tv_sec) \
n = 0x0UL; \
else { \
L32(n) = htonl(t.tv_sec + EPOCHDIFF); \
R32(n) = htonl((uint64_t)((4294.967296 * t.tv_usec) + .5)); \
} \
} while (0)
/* NTP control message header is 12 bytes, plus any data in the data
* field, plus null padding to the nearest 32-bit boundary per rfc.
*/
#define SIZEOF_NTPCM(m) (12 + ntohs(m.count) + ((m.count) ? 4 - (ntohs(m.count) % 4) : 0))
/* finally, a little helper or two for debugging: */
#define DBG(x) \
do { \
if (verbose > 1) { \
x; \
} \
} while (0);
#define PRINTSOCKADDR(x) \
do { \
printf("%u.%u.%u.%u", (x >> 24) & 0xff, (x >> 16) & 0xff, (x >> 8) & 0xff, x & 0xff); \
} while (0);
/* calculate the offset of the local clock */
static inline double calc_offset(const ntp_message *m, const struct timeval *t) {
double client_tx = NTP64asDOUBLE(m->origts);
double peer_rx = NTP64asDOUBLE(m->rxts);
double peer_tx = NTP64asDOUBLE(m->txts);
double client_rx = TVasDOUBLE((*t));
return (.5 * ((peer_tx - client_rx) + (peer_rx - client_tx)));
}
/* print out a ntp packet in human readable/debuggable format */
void print_ntp_message(const ntp_message *p) {
struct timeval ref;
struct timeval orig;
struct timeval rx;
struct timeval tx;
NTP64toTV(p->refts, ref);
NTP64toTV(p->origts, orig);
NTP64toTV(p->rxts, rx);
NTP64toTV(p->txts, tx);
printf("packet contents:\n");
printf("\tflags: 0x%.2x\n", p->flags);
printf("\t li=%d (0x%.2x)\n", LI(p->flags), p->flags & LI_MASK);
printf("\t vn=%d (0x%.2x)\n", VN(p->flags), p->flags & VN_MASK);
printf("\t mode=%d (0x%.2x)\n", MODE(p->flags), p->flags & MODE_MASK);
printf("\tstratum = %d\n", p->stratum);
printf("\tpoll = %g\n", pow(2, p->poll));
printf("\tprecision = %g\n", pow(2, p->precision));
printf("\trtdelay = %-.16g\n", NTP32asDOUBLE(p->rtdelay));
printf("\trtdisp = %-.16g\n", NTP32asDOUBLE(p->rtdisp));
printf("\trefid = %x\n", p->refid);
printf("\trefts = %-.16g\n", NTP64asDOUBLE(p->refts));
printf("\torigts = %-.16g\n", NTP64asDOUBLE(p->origts));
printf("\trxts = %-.16g\n", NTP64asDOUBLE(p->rxts));
printf("\ttxts = %-.16g\n", NTP64asDOUBLE(p->txts));
}
void setup_request(ntp_message *p) {
memset(p, 0, sizeof(ntp_message));
LI_SET(p->flags, LI_ALARM);
VN_SET(p->flags, 4);
MODE_SET(p->flags, MODE_CLIENT);
p->poll = 4;
p->precision = (int8_t)0xfa;
L16(p->rtdelay) = htons(1);
L16(p->rtdisp) = htons(1);
struct timeval t;
gettimeofday(&t, NULL);
TVtoNTP64(t, p->txts);
}
/* select the "best" server from a list of servers, and return its index.
* this is done by filtering servers based on stratum, dispersion, and
* finally round-trip delay. */
int best_offset_server(const ntp_server_results *slist, int nservers) {
int best_server = -1;
/* for each server */
for (int cserver = 0; cserver < nservers; cserver++) {
/* We don't want any servers that fails these tests */
/* Sort out servers that didn't respond or responede with a 0 stratum;
* stratum 0 is for reference clocks so no NTP server should ever report
* a stratum 0 */
if (slist[cserver].stratum == 0) {
if (verbose)
printf("discarding peer %d: stratum=%d\n", cserver, slist[cserver].stratum);
continue;
}
/* Sort out servers with error flags */
if (LI(slist[cserver].flags) == LI_ALARM) {
if (verbose)
printf("discarding peer %d: flags=%d\n", cserver, LI(slist[cserver].flags));
continue;
}
/* If we don't have a server yet, use the first one */
if (best_server == -1) {
best_server = cserver;
DBG(printf("using peer %d as our first candidate\n", best_server));
continue;
}
/* compare the server to the best one we've seen so far */
/* does it have an equal or better stratum? */
DBG(printf("comparing peer %d with peer %d\n", cserver, best_server));
if (slist[cserver].stratum <= slist[best_server].stratum) {
DBG(printf("stratum for peer %d <= peer %d\n", cserver, best_server));
/* does it have an equal or better dispersion? */
if (slist[cserver].rtdisp <= slist[best_server].rtdisp) {
DBG(printf("dispersion for peer %d <= peer %d\n", cserver, best_server));
/* does it have a better rtdelay? */
if (slist[cserver].rtdelay < slist[best_server].rtdelay) {
DBG(printf("rtdelay for peer %d < peer %d\n", cserver, best_server));
best_server = cserver;
DBG(printf("peer %d is now our best candidate\n", best_server));
}
}
}
}
if (best_server >= 0) {
DBG(printf("best server selected: peer %d\n", best_server));
return best_server;
}
DBG(printf("no peers meeting synchronization criteria :(\n"));
return -1;
}
/* do everything we need to get the total average offset
* - we use a certain amount of parallelization with poll() to ensure
* we don't waste time sitting around waiting for single packets.
* - we also "manually" handle resolving host names and connecting, because
* we have to do it in a way that our lazy macros don't handle currently :( */
double offset_request(const char *host, int *status) {
/* setup hints to only return results from getaddrinfo that we'd like */
struct addrinfo hints;
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = address_family;
hints.ai_protocol = IPPROTO_UDP;
hints.ai_socktype = SOCK_DGRAM;
/* fill in ai with the list of hosts resolved by the host name */
struct addrinfo *ai = NULL;
int ga_result = getaddrinfo(host, port, &hints, &ai);
if (ga_result != 0) {
die(STATE_UNKNOWN, "error getting address for %s: %s\n", host, gai_strerror(ga_result));
}
/* count the number of returned hosts, and allocate stuff accordingly */
int num_hosts = 0;
for (struct addrinfo *ai_tmp = ai; ai_tmp != NULL; ai_tmp = ai_tmp->ai_next) {
num_hosts++;
}
ntp_message *req = (ntp_message *)malloc(sizeof(ntp_message) * num_hosts);
if (req == NULL)
die(STATE_UNKNOWN, "can not allocate ntp message array");
int *socklist = (int *)malloc(sizeof(int) * num_hosts);
if (socklist == NULL)
die(STATE_UNKNOWN, "can not allocate socket array");
struct pollfd *ufds = (struct pollfd *)malloc(sizeof(struct pollfd) * num_hosts);
if (ufds == NULL)
die(STATE_UNKNOWN, "can not allocate socket array");
ntp_server_results *servers = (ntp_server_results *)malloc(sizeof(ntp_server_results) * num_hosts);
if (servers == NULL)
die(STATE_UNKNOWN, "can not allocate server array");
memset(servers, 0, sizeof(ntp_server_results) * num_hosts);
DBG(printf("Found %d peers to check\n", num_hosts));
/* setup each socket for writing, and the corresponding struct pollfd */
struct addrinfo *ai_tmp = ai;
for (int i = 0; ai_tmp; i++) {
socklist[i] = socket(ai_tmp->ai_family, SOCK_DGRAM, IPPROTO_UDP);
if (socklist[i] == -1) {
perror(NULL);
die(STATE_UNKNOWN, "can not create new socket");
}
if (connect(socklist[i], ai_tmp->ai_addr, ai_tmp->ai_addrlen)) {
/* don't die here, because it is enough if there is one server
answering in time. This also would break for dual ipv4/6 stacked
ntp servers when the client only supports on of them.
*/
DBG(printf("can't create socket connection on peer %i: %s\n", i, strerror(errno)));
} else {
ufds[i].fd = socklist[i];
ufds[i].events = POLLIN;
ufds[i].revents = 0;
}
ai_tmp = ai_tmp->ai_next;
}
/* now do AVG_NUM checks to each host. We stop before timeout/2 seconds
* have passed in order to ensure post-processing and jitter time. */
time_t start_ts = 0;
time_t now_time = 0;
now_time = start_ts = time(NULL);
int servers_completed = 0;
bool one_read = false;
while (servers_completed < num_hosts && now_time - start_ts <= socket_timeout / 2) {
/* loop through each server and find each one which hasn't
* been touched in the past second or so and is still lacking
* some responses. For each of these servers, send a new request,
* and update the "waiting" timestamp with the current time. */
now_time = time(NULL);
for (int i = 0; i < num_hosts; i++) {
if (servers[i].waiting < now_time && servers[i].num_responses < AVG_NUM) {
if (verbose && servers[i].waiting != 0)
printf("re-");
if (verbose)
printf("sending request to peer %d\n", i);
setup_request(&req[i]);
write(socklist[i], &req[i], sizeof(ntp_message));
servers[i].waiting = now_time;
break;
}
}
/* quickly poll for any sockets with pending data */
int servers_readable = poll(ufds, num_hosts, 100);
if (servers_readable == -1) {
perror("polling ntp sockets");
die(STATE_UNKNOWN, "communication errors");
}
/* read from any sockets with pending data */
for (int i = 0; servers_readable && i < num_hosts; i++) {
if (ufds[i].revents & POLLIN && servers[i].num_responses < AVG_NUM) {
if (verbose) {
printf("response from peer %d: ", i);
}
read(ufds[i].fd, &req[i], sizeof(ntp_message));
struct timeval recv_time;
gettimeofday(&recv_time, NULL);
DBG(print_ntp_message(&req[i]));
int respnum = servers[i].num_responses++;
servers[i].offset[respnum] = calc_offset(&req[i], &recv_time) + time_offset;
if (verbose) {
printf("offset %.10g\n", servers[i].offset[respnum]);
}
servers[i].stratum = req[i].stratum;
servers[i].rtdisp = NTP32asDOUBLE(req[i].rtdisp);
servers[i].rtdelay = NTP32asDOUBLE(req[i].rtdelay);
servers[i].waiting = 0;
servers[i].flags = req[i].flags;
servers_readable--;
one_read = true;
if (servers[i].num_responses == AVG_NUM)
servers_completed++;
}
}
/* lather, rinse, repeat. */
}
if (one_read == false) {
die(STATE_CRITICAL, "NTP CRITICAL: No response from NTP server\n");
}
/* now, pick the best server from the list */
double avg_offset = 0.;
int best_index = best_offset_server(servers, num_hosts);
if (best_index < 0) {
*status = STATE_UNKNOWN;
} else {
/* finally, calculate the average offset */
for (int i = 0; i < servers[best_index].num_responses; i++) {
avg_offset += servers[best_index].offset[i];
}
avg_offset /= servers[best_index].num_responses;
}
/* cleanup */
for (int j = 0; j < num_hosts; j++) {
close(socklist[j]);
}
free(socklist);
free(ufds);
free(servers);
free(req);
freeaddrinfo(ai);
if (verbose)
printf("overall average offset: %.10g\n", avg_offset);
return avg_offset;
}
int process_arguments(int argc, char **argv) {
static struct option longopts[] = {{"version", no_argument, 0, 'V'},
{"help", no_argument, 0, 'h'},
{"verbose", no_argument, 0, 'v'},
{"use-ipv4", no_argument, 0, '4'},
{"use-ipv6", no_argument, 0, '6'},
{"quiet", no_argument, 0, 'q'},
{"time-offset", optional_argument, 0, 'o'},
{"warning", required_argument, 0, 'w'},
{"critical", required_argument, 0, 'c'},
{"timeout", required_argument, 0, 't'},
{"hostname", required_argument, 0, 'H'},
{"port", required_argument, 0, 'p'},
{0, 0, 0, 0}};
if (argc < 2)
usage("\n");
while (true) {
int option = 0;
int option_char = getopt_long(argc, argv, "Vhv46qw:c:t:H:p:o:", longopts, &option);
if (option_char == -1 || option_char == EOF || option_char == 1)
break;
switch (option_char) {
case 'h':
print_help();
exit(STATE_UNKNOWN);
break;
case 'V':
print_revision(progname, NP_VERSION);
exit(STATE_UNKNOWN);
break;
case 'v':
verbose++;
break;
case 'q':
quiet = true;
break;
case 'w':
owarn = optarg;
break;
case 'c':
ocrit = optarg;
break;
case 'H':
if (!is_host(optarg))
usage2(_("Invalid hostname/address"), optarg);
server_address = strdup(optarg);
break;
case 'p':
port = strdup(optarg);
break;
case 't':
socket_timeout = atoi(optarg);
break;
case 'o':
time_offset = atoi(optarg);
break;
case '4':
address_family = AF_INET;
break;
case '6':
#ifdef USE_IPV6
address_family = AF_INET6;
#else
usage4(_("IPv6 support not available"));
#endif
break;
case '?':
/* print short usage statement if args not parsable */
usage5();
break;
}
}
if (server_address == NULL) {
usage4(_("Hostname was not supplied"));
}
return 0;
}
char *perfd_offset(double offset) {
return fperfdata("offset", offset, "s", true, offset_thresholds->warning->end, true, offset_thresholds->critical->end, false, 0, false,
0);
}
int main(int argc, char *argv[]) {
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
/* Parse extra opts if any */
argv = np_extra_opts(&argc, argv, progname);
if (process_arguments(argc, argv) == ERROR)
usage4(_("Could not parse arguments"));
set_thresholds(&offset_thresholds, owarn, ocrit);
/* initialize alarm signal handling */
signal(SIGALRM, socket_timeout_alarm_handler);
/* set socket timeout */
alarm(socket_timeout);
int offset_result = STATE_OK;
int result = STATE_OK;
double offset = offset_request(server_address, &offset_result);
if (offset_result == STATE_UNKNOWN) {
result = ((!quiet) ? STATE_UNKNOWN : STATE_CRITICAL);
} else {
result = get_status(fabs(offset), offset_thresholds);
}
char *result_line;
switch (result) {
case STATE_CRITICAL:
xasprintf(&result_line, _("NTP CRITICAL:"));
break;
case STATE_WARNING:
xasprintf(&result_line, _("NTP WARNING:"));
break;
case STATE_OK:
xasprintf(&result_line, _("NTP OK:"));
break;
default:
xasprintf(&result_line, _("NTP UNKNOWN:"));
break;
}
char *perfdata_line;
if (offset_result == STATE_UNKNOWN) {
xasprintf(&result_line, "%s %s", result_line, _("Offset unknown"));
xasprintf(&perfdata_line, "");
} else {
xasprintf(&result_line, "%s %s %.10g secs", result_line, _("Offset"), offset);
xasprintf(&perfdata_line, "%s", perfd_offset(offset));
}
printf("%s|%s\n", result_line, perfdata_line);
if (server_address != NULL)
free(server_address);
return result;
}
void print_help(void) {
print_revision(progname, NP_VERSION);
printf("Copyright (c) 2006 Sean Finney\n");
printf(COPYRIGHT, copyright, email);
printf("%s\n", _("This plugin checks the clock offset with the ntp server"));
printf("\n\n");
print_usage();
printf(UT_HELP_VRSN);
printf(UT_EXTRA_OPTS);
printf(UT_IPv46);
printf(UT_HOST_PORT, 'p', "123");
printf(" %s\n", "-q, --quiet");
printf(" %s\n", _("Returns UNKNOWN instead of CRITICAL if offset cannot be found"));
printf(" %s\n", "-w, --warning=THRESHOLD");
printf(" %s\n", _("Offset to result in warning status (seconds)"));
printf(" %s\n", "-c, --critical=THRESHOLD");
printf(" %s\n", _("Offset to result in critical status (seconds)"));
printf(" %s\n", "-o, --time_offset=INTEGER");
printf(" %s\n", _("Expected offset of the ntp server relative to local server (seconds)"));
printf(UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
printf(UT_VERBOSE);
printf("\n");
printf("%s\n", _("This plugin checks the clock offset between the local host and a"));
printf("%s\n", _("remote NTP server. It is independent of any commandline programs or"));
printf("%s\n", _("external libraries."));
printf("\n");
printf("%s\n", _("Notes:"));
printf(" %s\n", _("If you'd rather want to monitor an NTP server, please use"));
printf(" %s\n", _("check_ntp_peer."));
printf(" %s\n", _("--time-offset is useful for compensating for servers with known"));
printf(" %s\n", _("and expected clock skew."));
printf("\n");
printf(UT_THRESHOLDS_NOTES);
printf("\n");
printf("%s\n", _("Examples:"));
printf(" %s\n", ("./check_ntp_time -H ntpserv -w 0.5 -c 1"));
printf(UT_SUPPORT);
}
void print_usage(void) {
printf("%s\n", _("Usage:"));
printf(" %s -H <host> [-4|-6] [-w <warn>] [-c <crit>] [-v verbose] [-o <time offset>]\n", progname);
}