/*
* Copyright (c) 2020, Nico Weber <thakis@chromium.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#define _GNU_SOURCE
#include <LibCore/ArgsParser.h>
#include <arpa/inet.h>
#include <endian.h>
#include <math.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/uio.h>
// An NtpTimestamp is a 64-bit integer that's a 32.32 binary-fixed point number.
// The integral part in the upper 32 bits represents seconds since 1900-01-01.
// The fractional part in the lower 32 bits stores fractional bits times 2 ** 32.
typedef uint64_t NtpTimestamp;
struct [[gnu::packed]] NtpPacket
{
uint8_t li_vn_mode;
uint8_t stratum;
int8_t poll;
int8_t precision;
uint32_t root_delay;
uint32_t root_dispersion;
uint32_t reference_id;
NtpTimestamp reference_timestamp;
NtpTimestamp origin_timestamp;
NtpTimestamp receive_timestamp;
NtpTimestamp transmit_timestamp;
};
static_assert(sizeof(NtpPacket) == 48);
// NTP measures time in seconds since 1900-01-01, POSIX in seconds since 1970-01-01.
// 1900 wasn't a leap year, so there are 70/4 leap years between 1900 and 1970.
// Overflows a 32-bit signed int, but not a 32-bit unsigned int.
const unsigned SecondsFrom1900To1970 = (70u * 365u + 70u / 4u) * 24u * 60u * 60u;
static NtpTimestamp ntp_timestamp_from_timeval(const timeval& t)
{
ASSERT(t.tv_usec >= 0 && t.tv_usec < 1'000'000); // Fits in 20 bits when normalized.
// Seconds just need translation to the different origin.
uint32_t seconds = t.tv_sec + SecondsFrom1900To1970;
// Fractional bits are decimal fixed point (*1'000'000) in timeval, but binary fixed-point (* 2**32) in NTP timestamps.
uint32_t fractional_bits = static_cast<uint32_t>((static_cast<uint64_t>(t.tv_usec) << 32) / 1'000'000);
return (static_cast<NtpTimestamp>(seconds) << 32) | fractional_bits;
}
static timeval timeval_from_ntp_timestamp(const NtpTimestamp& ntp_timestamp)
{
timeval t;
t.tv_sec = static_cast<time_t>(ntp_timestamp >> 32) - SecondsFrom1900To1970;
t.tv_usec = static_cast<suseconds_t>((static_cast<uint64_t>(ntp_timestamp & 0xFFFFFFFFu) * 1'000'000) >> 32);
return t;
}
static String format_ntp_timestamp(NtpTimestamp ntp_timestamp)
{
char buffer[28]; // YYYY-MM-DDTHH:MM:SS.UUUUUUZ is 27 characters long.
timeval t = timeval_from_ntp_timestamp(ntp_timestamp);
struct tm tm;
gmtime_r(&t.tv_sec, &tm);
size_t written = strftime(buffer, sizeof(buffer), "%Y-%m-%dT%T.", &tm);
ASSERT(written == 20);
written += snprintf(buffer + written, sizeof(buffer) - written, "%06d", t.tv_usec);
ASSERT(written == 26);
buffer[written++] = 'Z';
buffer[written] = '\0';
return buffer;
}
int main(int argc, char** argv)
{
if (pledge("stdio inet dns settime", nullptr) < 0) {
perror("pledge");
return 1;
}
bool set_time = false;
// FIXME: Change to serenityos.pool.ntp.org once https://manage.ntppool.org/manage/vendor/zone?a=km5a8h&id=vz-14154g is approved.
const char* host = "time.google.com";
Core::ArgsParser args_parser;
args_parser.add_option(set_time, "Adjust system time (requires root)", "set", 's');
args_parser.add_positional_argument(host, "NTP server", "host", Core::ArgsParser::Required::No);
args_parser.parse(argc, argv);
if (!set_time) {
if (pledge("stdio inet dns", nullptr) < 0) {
perror("pledge");
return 1;
}
}
auto* hostent = gethostbyname(host);
if (!hostent) {
fprintf(stderr, "Lookup failed for '%s'\n", host);
return 1;
}
if (pledge(set_time ? "stdio inet settime" : "stdio inet", nullptr) < 0) {
perror("pledge");
return 1;
}
unveil(nullptr, nullptr);
int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (fd < 0) {
perror("socket");
return 1;
}
struct timeval timeout {
5, 0
};
if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout)) < 0) {
perror("setsockopt");
return 1;
}
int enable = 1;
if (setsockopt(fd, SOL_SOCKET, SO_TIMESTAMP, &enable, sizeof(enable)) < 0) {
perror("setsockopt");
return 1;
}
sockaddr_in peer_address;
memset(&peer_address, 0, sizeof(peer_address));
peer_address.sin_family = AF_INET;
peer_address.sin_port = htons(123);
peer_address.sin_addr.s_addr = *(const in_addr_t*)hostent->h_addr_list[0];
NtpPacket packet;
memset(&packet, 0, sizeof(packet));
packet.li_vn_mode = (4 << 3) | 3; // Version 4, client connection.
// The server will copy the transmit_timestamp to origin_timestamp in the reply.
timeval t;
gettimeofday(&t, nullptr);
packet.transmit_timestamp = htobe64(ntp_timestamp_from_timeval(t));
ssize_t rc;
rc = sendto(fd, &packet, sizeof(packet), 0, (const struct sockaddr*)&peer_address, sizeof(peer_address));
if (rc < 0) {
perror("sendto");
return 1;
}
if ((size_t)rc < sizeof(packet)) {
fprintf(stderr, "incomplete packet send\n");
return 1;
}
iovec iov { &packet, sizeof(packet) };
char control_message_buffer[CMSG_SPACE(sizeof(timeval))];
msghdr msg = { &peer_address, sizeof(peer_address), &iov, 1, control_message_buffer, sizeof(control_message_buffer), 0 };
rc = recvmsg(fd, &msg, 0);
if (rc < 0) {
perror("recvmsg");
return 1;
}
gettimeofday(&t, nullptr);
if ((size_t)rc < sizeof(packet)) {
fprintf(stderr, "incomplete packet recv\n");
return 1;
}
cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
ASSERT(cmsg->cmsg_level == SOL_SOCKET);
ASSERT(cmsg->cmsg_type == SCM_TIMESTAMP);
ASSERT(!CMSG_NXTHDR(&msg, cmsg));
timeval packet_t;
memcpy(&packet_t, CMSG_DATA(cmsg), sizeof(packet_t));
NtpTimestamp origin_timestamp = be64toh(packet.origin_timestamp);
NtpTimestamp receive_timestamp = be64toh(packet.receive_timestamp);
NtpTimestamp transmit_timestamp = be64toh(packet.transmit_timestamp);
NtpTimestamp destination_timestamp = ntp_timestamp_from_timeval(packet_t);
timersub(&t, &packet_t, &t);
if (set_time) {
// FIXME: Do all the time filtering described in 5905, or at least correct for time of flight.
timeval t = timeval_from_ntp_timestamp(transmit_timestamp);
if (settimeofday(&t, nullptr) < 0) {
perror("settimeofday");
return 1;
}
}
printf("NTP response from %s:\n", inet_ntoa(peer_address.sin_addr));
printf("Leap Information: %d\n", packet.li_vn_mode >> 6);
printf("Version Number: %d\n", (packet.li_vn_mode >> 3) & 7);
printf("Mode: %d\n", packet.li_vn_mode & 7);
printf("Stratum: %d\n", packet.stratum);
printf("Poll: %d\n", packet.stratum);
printf("Precision: %d\n", packet.precision);
printf("Root delay: %#x\n", ntohl(packet.root_delay));
printf("Root dispersion: %#x\n", ntohl(packet.root_dispersion));
printf("Reference ID: %#x\n", ntohl(packet.reference_id));
printf("Reference timestamp: %#016llx (%s)\n", be64toh(packet.reference_timestamp), format_ntp_timestamp(be64toh(packet.reference_timestamp)).characters());
printf("Origin timestamp: %#016llx (%s)\n", origin_timestamp, format_ntp_timestamp(origin_timestamp).characters());
printf("Receive timestamp: %#016llx (%s)\n", receive_timestamp, format_ntp_timestamp(receive_timestamp).characters());
printf("Transmit timestamp: %#016llx (%s)\n", transmit_timestamp, format_ntp_timestamp(transmit_timestamp).characters());
printf("Destination timestamp: %#016llx (%s)\n", destination_timestamp, format_ntp_timestamp(destination_timestamp).characters());
// When the system isn't under load, user-space t and packet_t are identical. If a shell with `yes` is running, it can be as high as 30ms in this program,
// which gets user-space time immediately after the recvmsg() call. In programs that have an event loop reading from multiple sockets, it could be higher.
printf("Receive latency: %lld.%06d s\n", t.tv_sec, t.tv_usec);
// Parts of the "Clock Filter" computations, https://tools.ietf.org/html/rfc5905#section-10
NtpTimestamp T1 = origin_timestamp;
NtpTimestamp T2 = receive_timestamp;
NtpTimestamp T3 = transmit_timestamp;
NtpTimestamp T4 = destination_timestamp;
auto timestamp_difference_in_seconds = [](NtpTimestamp from, NtpTimestamp to) {
return static_cast<int64_t>(to - from) / pow(2.0, 32);
};
// The network round-trip time of the request.
// T4-T1 is the wall clock roundtrip time, in local ticks.
// T3-T2 is the server side processing time, in server ticks.
double delay_s = timestamp_difference_in_seconds(T1, T4) - timestamp_difference_in_seconds(T2, T3);
// The offset from local time to server time, ignoring network delay.
// Both T2-T1 and T3-T4 estimate this; this takes the average of both.
// Or, equivalently, (T1+T4)/2 estimates local time, (T2+T3)/2 estimate server time, this is the difference.
double offset_s = 0.5 * (timestamp_difference_in_seconds(T1, T2) + timestamp_difference_in_seconds(T4, T3));
printf("Delay: %f\n", delay_s);
printf("Offset: %f\n", offset_s);
}