--- /dev/null
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2014 Kay Sievers
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+/*
+ * "Simple Network Time Protocol Version 4 (SNTPv4) is a subset of the
+ * Network Time Protocol (NTP) used to synchronize computer clocks in
+ * the Internet. SNTPv4 can be used when the ultimate performance of
+ * a full NTP implementation based on RFC 1305 is neither needed nor
+ * justified."
+ *
+ * "Unlike most NTP clients, SNTP clients normally operate with only a
+ * single server at a time."
+ *
+ * http://tools.ietf.org/html/rfc4330
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <time.h>
+#include <math.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <sys/timex.h>
+#include <sys/socket.h>
+
+#include "util.h"
+#include "sparse-endian.h"
+#include "log.h"
+#include "sd-event.h"
+#include "timedate-sntp.h"
+
+#ifndef ADJ_SETOFFSET
+#define ADJ_SETOFFSET 0x0100 /* add 'time' to current time */
+#endif
+
+/* Maximum delta in seconds which the system clock is gradually adjusted
+ * to approach the network time. Deltas larger that this are set by letting
+ * the system time jump. The maximum for adjtime is 500ms.
+ */
+#define NTP_MAX_ADJUST 0.2
+
+/*
+ * "Define the required accuracy of the system clock, then calculate the
+ * maximum timeout. Use the longest maximum timeout possible given the system
+ * constraints to minimize time server aggregate load."
+ *
+ * "A client MUST NOT under any conditions use a poll interval less
+ * than 15 seconds."
+ */
+#define NTP_POLL_INTERVAL_MIN_SEC 16
+#define NTP_POLL_INTERVAL_MAX_SEC 2048
+#define NTP_POLL_ACCURACY_SEC 0.1
+
+#define NTP_LEAP_PLUSSEC 1
+#define NTP_LEAP_MINUSSEC 2
+#define NTP_LEAP_NOTINSYNC 3
+#define NTP_MODE_CLIENT 3
+#define NTP_MODE_SERVER 4
+#define NTP_FIELD_LEAP(f) (((f) >> 6) & 3)
+#define NTP_FIELD_VERSION(f) (((f) >> 3) & 7)
+#define NTP_FIELD_MODE(f) ((f) & 7)
+#define NTP_FIELD(l, v, m) (((l) << 6) | ((v) << 3) | (m))
+
+/*
+ * "NTP timestamps are represented as a 64-bit unsigned fixed-point number,
+ * in seconds relative to 0h on 1 January 1900."
+ */
+#define OFFSET_1900_1970 2208988800UL
+
+struct ntp_ts {
+ be32_t sec;
+ be32_t frac;
+} _packed_;
+
+struct ntp_ts_short {
+ be16_t sec;
+ be16_t frac;
+} _packed_;
+
+struct ntp_msg {
+ uint8_t field;
+ uint8_t stratum;
+ int8_t poll;
+ int8_t precision;
+ struct ntp_ts_short root_delay;
+ struct ntp_ts_short root_dispersion;
+ char refid[4];
+ struct ntp_ts reference_time;
+ struct ntp_ts origin_time;
+ struct ntp_ts recv_time;
+ struct ntp_ts trans_time;
+} _packed_;
+
+struct SNTPContext {
+ sd_event_source *event_receive;
+ sd_event_source *event_timer;
+
+ char *server;
+ struct sockaddr_in server_addr;
+ int server_socket;
+ uint64_t packet_count;
+
+ struct timespec trans_time_mon;
+ struct timespec trans_time;
+ bool pending;
+
+ usec_t poll_interval;
+
+ struct {
+ double offset;
+ double delay;
+ } samples[8];
+ unsigned int samples_idx;
+ double samples_jitter;
+};
+
+static int sntp_arm_timer(SNTPContext *sntp);
+
+static int log2i(int a) {
+ int exp = 0;
+
+ assert(a > 0);
+
+ while (a > 0) {
+ a >>= 1;
+ exp++;
+ }
+
+ return exp;
+}
+
+static double log2d(int a) {
+ if (a < 0)
+ return 1.0 / (1UL << - a);
+ return 1UL << a;
+}
+
+static double ntp_ts_to_d(const struct ntp_ts *ts) {
+ return be32toh(ts->sec) + ((double)be32toh(ts->frac) / UINT_MAX);
+}
+
+static double tv_to_d(const struct timeval *tv) {
+ return tv->tv_sec + (1.0e-6 * tv->tv_usec);
+}
+
+static double ts_to_d(const struct timespec *ts) {
+ return ts->tv_sec + (1.0e-9 * ts->tv_nsec);
+}
+
+static void d_to_tv(double d, struct timeval *tv) {
+ tv->tv_sec = (long)d;
+ tv->tv_usec = (d - tv->tv_sec) * 1000 * 1000;
+
+ /* the kernel expects -0.3s as {-1, 7000.000} */
+ if (tv->tv_usec < 0) {
+ tv->tv_sec -= 1;
+ tv->tv_usec += 1000 * 1000;
+ }
+}
+
+static double square(double d) {
+ return d * d;
+}
+
+static int sntp_send_request(SNTPContext *sntp) {
+ struct ntp_msg ntpmsg = {};
+ struct sockaddr_in addr = {};
+ ssize_t len;
+ int r;
+
+ /*
+ * "The client initializes the NTP message header, sends the request
+ * to the server, and strips the time of day from the Transmit
+ * Timestamp field of the reply. For this purpose, all the NTP
+ * header fields are set to 0, except the Mode, VN, and optional
+ * Transmit Timestamp fields."
+ */
+ ntpmsg.field = NTP_FIELD(0, 4, NTP_MODE_CLIENT);
+
+ /*
+ * Set transmit timestamp, remember it; the server will send that back
+ * as the origin timestamp and we have an indication that this is the
+ * matching answer to our request.
+ *
+ * The actual value does not matter, We do not care about the correct
+ * NTP UINT_MAX fraction, we just pass the plain nanosecond value.
+ */
+ clock_gettime(CLOCK_MONOTONIC, &sntp->trans_time_mon);
+ clock_gettime(CLOCK_REALTIME, &sntp->trans_time);
+ ntpmsg.trans_time.sec = htobe32(sntp->trans_time.tv_sec + OFFSET_1900_1970);
+ ntpmsg.trans_time.frac = htobe32(sntp->trans_time.tv_nsec);
+
+ addr.sin_family = AF_INET;
+ addr.sin_port = htobe16(123);
+ addr.sin_addr.s_addr = inet_addr(sntp->server);
+ len = sendto(sntp->server_socket, &ntpmsg, sizeof(ntpmsg), MSG_DONTWAIT, &addr, sizeof(addr));
+ if (len < 0) {
+ log_debug("Sending NTP request to %s failed: %m", sntp->server);
+ return -errno;
+ }
+
+ sntp->pending = true;
+
+ /* re-arm timer for next poll interval, in case the packet never arrives back */
+ r = sntp_arm_timer(sntp);
+ if (r < 0)
+ return r;
+
+ log_debug("Sent NTP request to: %s", sntp->server);
+ return 0;
+}
+
+static int sntp_timer(sd_event_source *source, usec_t usec, void *userdata) {
+ SNTPContext *sntp = userdata;
+
+ assert(sntp);
+
+ sntp_send_request(sntp);
+ return 0;
+}
+
+static int sntp_arm_timer(SNTPContext *sntp) {
+ sd_event *e;
+ int r;
+
+ assert(sntp);
+ assert(sntp->event_receive);
+
+ if (sntp->poll_interval <= 0) {
+ sntp->event_timer = sd_event_source_unref(sntp->event_timer);
+ return 0;
+ }
+
+ if (sntp->event_timer) {
+ r = sd_event_source_set_time(sntp->event_timer, now(CLOCK_MONOTONIC) + sntp->poll_interval);
+ if (r < 0)
+ return r;
+
+ return sd_event_source_set_enabled(sntp->event_timer, SD_EVENT_ONESHOT);
+ }
+
+ e = sd_event_source_get_event(sntp->event_receive);
+ r = sd_event_add_monotonic(e, &sntp->event_timer, now(CLOCK_MONOTONIC) + sntp->poll_interval, 0, sntp_timer, sntp);
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+static int sntp_adjust_clock(SNTPContext *sntp, double offset, int leap_sec) {
+ struct timex tmx = {};
+ int r;
+
+ /*
+ * For small deltas, tell the kernel to gradually adjust the system
+ * clock to the NTP time, larger deltas are just directly set.
+ *
+ * Clear STA_UNSYNC, it will enable the kernel's 11-minute mode, which
+ * syncs the system time periodically to the hardware clock.
+ */
+ if (offset < NTP_MAX_ADJUST && offset > -NTP_MAX_ADJUST) {
+ int constant;
+
+ constant = log2i(sntp->poll_interval / USEC_PER_SEC) - 5;
+
+ tmx.modes |= ADJ_STATUS | ADJ_OFFSET | ADJ_TIMECONST;
+ tmx.status = STA_PLL;
+ tmx.offset = offset * 1000 * 1000;
+ tmx.constant = constant;
+
+ log_debug(" adjust (slew): %+f sec\n", (double)tmx.offset / USEC_PER_SEC);
+ } else {
+ tmx.modes = ADJ_SETOFFSET;
+ d_to_tv(offset, &tmx.time);
+ log_debug(" adjust (jump): %+f sec\n", tv_to_d(&tmx.time));
+ }
+
+ switch (leap_sec) {
+ case 1:
+ tmx.status |= STA_INS;
+ break;
+ case -1:
+ tmx.status |= STA_DEL;
+ break;
+ }
+
+ r = clock_adjtime(CLOCK_REALTIME, &tmx);
+ if (r < 0)
+ return r;
+
+ log_debug(" status : %04i %s\n"
+ " time now : %li.%06li\n"
+ " constant : %li\n"
+ " offset : %+f sec\n"
+ " freq offset : %+li (%+.3f ppm)\n",
+ tmx.status, tmx.status & STA_UNSYNC ? "" : "sync",
+ tmx.time.tv_sec, tmx.time.tv_usec,
+ tmx.constant,
+ (double)tmx.offset / USEC_PER_SEC,
+ tmx.freq, (double)tmx.freq / 65536);
+
+ return 0;
+}
+
+static bool sntp_sample_spike_detection(SNTPContext *sntp, double offset, double delay) {
+ unsigned int i, idx_cur, idx_new, idx_min;
+ double jitter;
+ bool spike;
+
+ /* store the current data in our samples array */
+ idx_cur = sntp->samples_idx;
+ idx_new = (idx_cur + 1) % ELEMENTSOF(sntp->samples);
+ sntp->samples_idx = idx_new;
+ sntp->samples[idx_new].offset = offset;
+ sntp->samples[idx_new].delay = delay;
+
+ sntp->packet_count++;
+
+ /*
+ * Spike detection; compare the difference between the
+ * current offset to the previous offset and jitter.
+ */
+ spike = sntp->packet_count > 2 && fabs(offset - sntp->samples[idx_cur].offset) > sntp->samples_jitter * 3;
+
+ /* calculate new jitter value from the RMS differences relative to the lowest delay sample */
+ for (idx_min = idx_cur, i = 0; i < ELEMENTSOF(sntp->samples); i++)
+ if (sntp->samples[i].delay > 0 && sntp->samples[i].delay < sntp->samples[idx_min].delay)
+ idx_min = i;
+
+ for (jitter = 0, i = 0; i < ELEMENTSOF(sntp->samples); i++)
+ jitter += square(sntp->samples[i].offset - sntp->samples[idx_min].offset);
+ sntp->samples_jitter = sqrt(jitter / (ELEMENTSOF(sntp->samples) - 1));
+
+ return spike;
+}
+
+static void snmp_adjust_poll(SNTPContext *sntp, double offset, bool spike) {
+ double delta;
+
+ if (spike) {
+ if (sntp->poll_interval > NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC)
+ sntp->poll_interval /= 2;
+ return;
+ }
+
+ delta = fabs(offset);
+
+ /* set to minimal poll interval */
+ if (delta > NTP_POLL_ACCURACY_SEC) {
+ sntp->poll_interval = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+ return;
+ }
+
+ /* increase polling interval */
+ if (delta < NTP_POLL_ACCURACY_SEC * 0.25) {
+ if (sntp->poll_interval < NTP_POLL_INTERVAL_MAX_SEC * USEC_PER_SEC)
+ sntp->poll_interval *= 2;
+ return;
+ }
+
+ /* decrease polling interval */
+ if (delta > NTP_POLL_ACCURACY_SEC * 0.75) {
+ if (sntp->poll_interval > NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC)
+ sntp->poll_interval /= 2;
+ return;
+ }
+}
+
+static int sntp_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+ SNTPContext *sntp = userdata;
+ unsigned char buf[sizeof(struct ntp_msg)];
+ struct iovec iov = {
+ .iov_base = buf,
+ .iov_len = sizeof(buf),
+ };
+ union {
+ struct cmsghdr cmsghdr;
+ uint8_t buf[CMSG_SPACE(sizeof(struct timeval))];
+ } control;
+ struct sockaddr_in server_addr;
+ struct msghdr msghdr = {
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = &control,
+ .msg_controllen = sizeof(control),
+ .msg_name = &server_addr,
+ .msg_namelen = sizeof(server_addr),
+ };
+ struct cmsghdr *cmsg;
+ struct timespec now;
+ struct timeval *recv_time;
+ ssize_t len;
+ struct ntp_msg *ntpmsg;
+ double origin, recv, trans, dest;
+ double delay, offset;
+ bool spike;
+ int leap_sec;
+ int r;
+
+ if (revents & (EPOLLHUP|EPOLLERR)) {
+ log_debug("Server connection returned error, closing.");
+ sntp_server_disconnect(sntp);
+ return -ENOTCONN;
+ }
+
+ len = recvmsg(fd, &msghdr, MSG_DONTWAIT);
+ if (len < 0) {
+ log_debug("Error receiving message, disconnecting");
+ return -EINVAL;
+ }
+
+ if (iov.iov_len < sizeof(struct ntp_msg)) {
+ log_debug("Invalid response from server, disconnecting");
+ return -EINVAL;
+ }
+
+ if (sntp->server_addr.sin_addr.s_addr != server_addr.sin_addr.s_addr) {
+ log_debug("Response from unknown server, disconnecting");
+ return -EINVAL;
+ }
+
+ recv_time = NULL;
+ for (cmsg = CMSG_FIRSTHDR(&msghdr); cmsg; cmsg = CMSG_NXTHDR(&msghdr, cmsg)) {
+ if (cmsg->cmsg_level != SOL_SOCKET)
+ continue;
+
+ switch (cmsg->cmsg_type) {
+ case SCM_TIMESTAMP:
+ recv_time = (struct timeval *) CMSG_DATA(cmsg);
+ break;
+ }
+ }
+ if (!recv_time) {
+ log_debug("Invalid packet timestamp, disconnecting");
+ return -EINVAL;
+ }
+
+ ntpmsg = iov.iov_base;
+ if (!sntp->pending) {
+ log_debug("Unexpected reply, ignoring");
+ return 0;
+ }
+ sntp->pending = false;
+
+ /* check our "time cookie" (we just stored nanoseconds in the fraction field) */
+ if (be32toh(ntpmsg->origin_time.sec) != sntp->trans_time.tv_sec + OFFSET_1900_1970||
+ be32toh(ntpmsg->origin_time.frac) != sntp->trans_time.tv_nsec) {
+ log_debug("Invalid reply, not our transmit time, ignoring");
+ return 0;
+ }
+
+ if (NTP_FIELD_LEAP(ntpmsg->field) == NTP_LEAP_NOTINSYNC) {
+ log_debug("Server is not synchronized, disconnecting");
+ return -EINVAL;
+ }
+
+ if (NTP_FIELD_VERSION(ntpmsg->field) != 4) {
+ log_debug("Response NTPv%d, disconnecting", NTP_FIELD_VERSION(ntpmsg->field));
+ return -EINVAL;
+ }
+
+ if (NTP_FIELD_MODE(ntpmsg->field) != NTP_MODE_SERVER) {
+ log_debug("Unsupported mode %d, disconnecting", NTP_FIELD_MODE(ntpmsg->field));
+ return -EINVAL;
+ }
+
+ /* announce leap seconds */
+ if (NTP_FIELD_LEAP(ntpmsg->field) & NTP_LEAP_PLUSSEC)
+ leap_sec = 1;
+ else if (NTP_FIELD_LEAP(ntpmsg->field) & NTP_LEAP_MINUSSEC)
+ leap_sec = -1;
+ else
+ leap_sec = 0;
+
+ /*
+ * "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 system clock offset t are defined as:
+ * d = (T4 - T1) - (T3 - T2) t = ((T2 - T1) + (T3 - T4)) / 2"
+ */
+ clock_gettime(CLOCK_MONOTONIC, &now);
+ origin = tv_to_d(recv_time) - (ts_to_d(&now) - ts_to_d(&sntp->trans_time_mon)) + OFFSET_1900_1970;
+ recv = ntp_ts_to_d(&ntpmsg->recv_time);
+ trans = ntp_ts_to_d(&ntpmsg->trans_time);
+ dest = tv_to_d(recv_time) + OFFSET_1900_1970;
+
+ offset = ((recv - origin) + (trans - dest)) / 2;
+ delay = (dest - origin) - (trans - recv);
+
+ spike = sntp_sample_spike_detection(sntp, offset, delay);
+
+ snmp_adjust_poll(sntp, offset, spike);
+
+ log_debug("NTP response:\n"
+ " leap : %u\n"
+ " version : %u\n"
+ " mode : %u\n"
+ " stratum : %u\n"
+ " precision : %f sec (%d)\n"
+ " reference : %.4s\n"
+ " origin : %f\n"
+ " recv : %f\n"
+ " transmit : %f\n"
+ " dest : %f\n"
+ " offset : %+f sec\n"
+ " delay : %+f sec\n"
+ " packet count : %llu\n"
+ " jitter/spike : %f (%s)\n"
+ " poll interval: %llu\n",
+ NTP_FIELD_LEAP(ntpmsg->field),
+ NTP_FIELD_VERSION(ntpmsg->field),
+ NTP_FIELD_MODE(ntpmsg->field),
+ ntpmsg->stratum,
+ log2d(ntpmsg->precision), ntpmsg->precision,
+ ntpmsg->stratum == 1 ? ntpmsg->refid : "n/a",
+ origin - OFFSET_1900_1970,
+ recv - OFFSET_1900_1970,
+ trans - OFFSET_1900_1970,
+ dest - OFFSET_1900_1970,
+ offset, delay,
+ (unsigned long long)sntp->packet_count,
+ sntp->samples_jitter, spike ? "yes" : "no",
+ sntp->poll_interval / USEC_PER_SEC);
+
+ log_info("%4llu %s %+12f", sntp->poll_interval / USEC_PER_SEC, spike ? "y" : "n", offset);
+
+ if (!spike) {
+ r = sntp_adjust_clock(sntp, offset, leap_sec);
+ if (r < 0)
+ log_error("Failed to call clock_adjtime(): %m");
+ }
+
+ r = sntp_arm_timer(sntp);
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+int sntp_server_connect(SNTPContext *sntp, const char *server) {
+ _cleanup_free_ char *s = NULL;
+
+ assert(sntp);
+ assert(server);
+ assert(sntp->server_socket >= 0);
+
+ s = strdup(server);
+ if (!s)
+ return -ENOMEM;
+
+ free(sntp->server);
+ sntp->server = s;
+ s = NULL;
+
+ zero(sntp->server_addr);
+ sntp->server_addr.sin_family = AF_INET;
+ sntp->server_addr.sin_addr.s_addr = inet_addr(server);
+
+ sntp->poll_interval = 2 * NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+
+ return sntp_send_request(sntp);
+}
+
+void sntp_server_disconnect(SNTPContext *sntp) {
+ if (!sntp->server)
+ return;
+
+ sntp->event_timer = sd_event_source_unref(sntp->event_timer);
+ sntp->event_receive = sd_event_source_unref(sntp->event_receive);
+ if (sntp->server_socket > 0)
+ close(sntp->server_socket);
+ sntp->server_socket = -1;
+ zero(sntp->server_addr);
+ free(sntp->server);
+ sntp->server = NULL;
+}
+
+int sntp_new(SNTPContext **sntp, sd_event *e) {
+ _cleanup_free_ SNTPContext *c;
+ _cleanup_close_ int fd = -1;
+ struct sockaddr_in addr;
+ const int on = 1;
+ const int tos = IPTOS_LOWDELAY;
+ int r;
+
+ c = new0(SNTPContext, 1);
+ if (!c)
+ return -ENOMEM;
+
+ fd = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+ if (fd < 0)
+ return -errno;
+
+ zero(addr);
+ addr.sin_family = AF_INET;
+ r = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
+ if (r < 0)
+ return -errno;
+
+ r = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof(on));
+ if (r < 0)
+ return -errno;
+
+ r = setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
+ if (r < 0)
+ return -errno;
+
+ r = sd_event_add_io(e, &c->event_receive, fd, EPOLLIN, sntp_receive_response, c);
+ if (r < 0)
+ return r;
+
+ c->server_socket = fd;
+ fd = -1;
+
+ *sntp = c;
+ c = NULL;
+
+ return 0;
+}
+
+SNTPContext *sntp_unref(SNTPContext *sntp) {
+ sntp_server_disconnect(sntp);
+ free(sntp);
+ return NULL;
+}
~ianmdlvl / elogind.git / commitdiff