forked from lthn/blockchain
270 lines
10 KiB
C++
270 lines
10 KiB
C++
// Copyright (c) 2019-2022 Zano Project
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// Note: class udp_blocking_client is a slightly modified version of an example
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// taken from https://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/example/timeouts/blocking_udp_client.cpp
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//
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// Copyright (c) 2003-2012 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include <cstdlib>
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#include <iostream>
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#include <boost/asio/deadline_timer.hpp>
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#include <boost/asio/io_service.hpp>
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#include <boost/asio/ip/udp.hpp>
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#include <boost/bind/bind.hpp>
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#include <boost/date_time/posix_time/posix_time_types.hpp>
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#include <boost/array.hpp>
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#include <epee/include/misc_log_ex.h>
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#include <chrono>
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#include "ntp.h"
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using boost::asio::deadline_timer;
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using boost::asio::ip::udp;
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//----------------------------------------------------------------------
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//
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// This class manages socket timeouts by applying the concept of a deadline.
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// Each asynchronous operation is given a deadline by which it must complete.
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// Deadlines are enforced by an "actor" that persists for the lifetime of the
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// client object:
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//
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// +----------------+
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// | |
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// | check_deadline |<---+
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// | | |
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// +----------------+ | async_wait()
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// | |
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// +---------+
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//
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// If the actor determines that the deadline has expired, any outstanding
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// socket operations are cancelled. The socket operations themselves are
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// implemented as transient actors:
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//
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// +---------------+
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// | |
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// | receive |
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// | |
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// +---------------+
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// |
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// async_- | +----------------+
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// receive() | | |
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// +--->| handle_receive |
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// | |
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// +----------------+
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//
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// The client object runs the io_service to block thread execution until the
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// actor completes.
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//
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namespace
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{
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class udp_blocking_client
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{
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public:
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udp_blocking_client(const udp::endpoint& listen_endpoint, udp::socket& socket, boost::asio::io_service& io_service)
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: socket_(socket),
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io_service_(io_service),
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deadline_(io_service)
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{
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// No deadline is required until the first socket operation is started. We
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// set the deadline to positive infinity so that the actor takes no action
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// until a specific deadline is set.
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deadline_.expires_at(boost::posix_time::pos_infin);
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// Start the persistent actor that checks for deadline expiry.
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check_deadline();
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}
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std::size_t receive(const boost::asio::mutable_buffer& buffer,
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boost::posix_time::time_duration timeout, boost::system::error_code& ec)
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{
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// Set a deadline for the asynchronous operation.
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deadline_.expires_from_now(timeout);
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// Set up the variables that receive the result of the asynchronous
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// operation. The error code is set to would_block to signal that the
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// operation is incomplete. Asio guarantees that its asynchronous
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// operations will never fail with would_block, so any other value in
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// ec indicates completion.
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ec = boost::asio::error::would_block;
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std::size_t length = 0;
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// Start the asynchronous operation itself. The handle_receive function
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// used as a callback will update the ec and length variables.
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socket_.async_receive(boost::asio::buffer(buffer),
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boost::bind(&udp_blocking_client::handle_receive, boost::placeholders::_1, boost::placeholders::_2, &ec, &length));
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// Block until the asynchronous operation has completed.
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do io_service_.run_one(); while (ec == boost::asio::error::would_block);
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return length;
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}
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private:
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void check_deadline()
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{
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// Check whether the deadline has passed. We compare the deadline against
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// the current time since a new asynchronous operation may have moved the
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// deadline before this actor had a chance to run.
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if (deadline_.expires_at() <= deadline_timer::traits_type::now())
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{
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// The deadline has passed. The outstanding asynchronous operation needs
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// to be cancelled so that the blocked receive() function will return.
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//
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// Please note that cancel() has portability issues on some versions of
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// Microsoft Windows, and it may be necessary to use close() instead.
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// Consult the documentation for cancel() for further information.
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socket_.cancel();
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// There is no longer an active deadline. The expiry is set to positive
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// infinity so that the actor takes no action until a new deadline is set.
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deadline_.expires_at(boost::posix_time::pos_infin);
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}
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// Put the actor back to sleep.
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deadline_.async_wait(boost::bind(&udp_blocking_client::check_deadline, this));
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}
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static void handle_receive(
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const boost::system::error_code& ec, std::size_t length,
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boost::system::error_code* out_ec, std::size_t* out_length)
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{
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*out_ec = ec;
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*out_length = length;
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}
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private:
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boost::asio::io_service& io_service_;
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udp::socket& socket_;
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deadline_timer deadline_;
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};
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#pragma pack(push, 1)
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struct ntp_packet
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{
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uint8_t li_vn_mode; // Eight bits. li, vn, and mode.
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// li. Two bits. Leap indicator.
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// vn. Three bits. Version number of the protocol.
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// mode. Three bits. Client will pick mode 3 for client.
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uint8_t stratum; // Eight bits. Stratum level of the local clock.
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uint8_t poll; // Eight bits. Maximum interval between successive messages.
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uint8_t precision; // Eight bits. Precision of the local clock.
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uint32_t rootDelay; // 32 bits. Total round trip delay time.
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uint32_t rootDispersion; // 32 bits. Max error aloud from primary clock source.
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uint32_t refId; // 32 bits. Reference clock identifier.
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uint32_t refTm_s; // 32 bits. Reference time-stamp seconds.
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uint32_t refTm_f; // 32 bits. Reference time-stamp fraction of a second.
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uint64_t orig_tm; // 64 bits. Originate time-stamp (set by client)
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uint32_t rxTm_s; // 32 bits. Received time-stamp seconds.
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uint32_t rxTm_f; // 32 bits. Received time-stamp fraction of a second.
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uint32_t txTm_s; // 32 bits and the most important field the client cares about. Transmit time-stamp seconds.
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uint32_t txTm_f; // 32 bits. Transmit time-stamp fraction of a second.
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}; // Total: 384 bits or 48 bytes.
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#pragma pack(pop)
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static_assert(sizeof(ntp_packet) == 48, "ntp_packet has invalid size");
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} // namespace
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namespace tools
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{
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int64_t get_ntp_time(const std::string& host_name, size_t timeout_sec)
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{
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try
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{
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boost::asio::io_service io_service;
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boost::asio::ip::udp::resolver resolver(io_service);
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boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), host_name, "ntp");
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boost::asio::ip::udp::endpoint receiver_endpoint = *resolver.resolve(query);
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boost::asio::ip::udp::socket socket(io_service);
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socket.open(boost::asio::ip::udp::v4());
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ntp_packet packet_sent = AUTO_VAL_INIT(packet_sent);
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packet_sent.li_vn_mode = 0x1b;
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auto packet_sent_time = std::chrono::high_resolution_clock::now();
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auto send_res = socket.send_to(boost::asio::buffer(&packet_sent, sizeof packet_sent), receiver_endpoint);
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if (send_res != sizeof packet_sent)
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{
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LOG_PRINT_L3("NTP: get_ntp_time(" << host_name << "): wrong send_res: " << send_res << ", expected sizeof packet_sent = " << sizeof packet_sent);
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return 0;
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}
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ntp_packet packet_received = AUTO_VAL_INIT(packet_received);
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boost::asio::ip::udp::endpoint sender_endpoint;
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udp_blocking_client ubc(sender_endpoint, socket, io_service);
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boost::system::error_code ec;
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ubc.receive(boost::asio::buffer(&packet_received, sizeof packet_received), boost::posix_time::seconds(static_cast<long>(timeout_sec)), ec);
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if (ec)
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{
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LOG_PRINT_L3("NTP: get_ntp_time(" << host_name << "): boost error: " << ec.message());
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return 0;
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}
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auto packet_received_time = std::chrono::high_resolution_clock::now();
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int64_t roundtrip_mcs = std::chrono::duration_cast<std::chrono::microseconds>(packet_received_time - packet_sent_time).count();
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uint64_t roundtrip_s = roundtrip_mcs > 2000000 ? roundtrip_mcs / 2000000 : 0;
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time_t ntp_time = ntohl(packet_received.txTm_s);
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if (ntp_time <= 2208988800U)
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{
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LOG_PRINT_L3("NTP: get_ntp_time(" << host_name << "): wrong txTm_s: " << packet_received.txTm_s);
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return 0;
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}
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// LOG_PRINT_L2("NTP: get_ntp_time(" << host_name << "): RAW time received: " << ntp_time << ", refTm_s: " << ntohl(packet_received.refTm_s) << ", stratum: " << packet_received.stratum << ", round: " << roundtrip_mcs);
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ntp_time -= 2208988800U; // Unix time starts from 01/01/1970 == 2208988800U
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ntp_time += roundtrip_s;
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return ntp_time;
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}
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catch (const std::exception& e)
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{
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LOG_PRINT_L2("NTP: get_ntp_time(" << host_name << "): exception: " << e.what());
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return 0;
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}
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catch (...)
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{
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LOG_PRINT_L2("NTP: get_ntp_time(" << host_name << "): unknown exception");
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return 0;
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}
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}
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#define TIME_SYNC_NTP_SERVERS "time1.google.com", "time2.google.com", "time3.google.com", "time4.google.com" /* , "pool.ntp.org" -- we need to request a vender zone before using this pool */
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#define TIME_SYNC_NTP_TIMEOUT_SEC 5
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#define TIME_SYNC_NTP_ATTEMPTS_COUNT 3 // max number of attempts when getting time from NTP server
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int64_t get_ntp_time()
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{
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static const std::vector<std::string> ntp_servers { TIME_SYNC_NTP_SERVERS };
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for (size_t att = 0; att < TIME_SYNC_NTP_ATTEMPTS_COUNT; ++att)
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{
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const std::string& ntp_server = ntp_servers[att % ntp_servers.size()];
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LOG_PRINT_L3("NTP: trying to get time from " << ntp_server);
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int64_t time = get_ntp_time(ntp_server, TIME_SYNC_NTP_TIMEOUT_SEC);
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if (time > 0)
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{
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LOG_PRINT_L3("NTP: " << ntp_server << " responded with " << time << " (" << epee::misc_utils::get_time_str_v2(time) << ")");
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return time;
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}
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}
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LOG_PRINT_RED("NTP: unable to get time from NTP with " << TIME_SYNC_NTP_ATTEMPTS_COUNT << " trials", LOG_LEVEL_2);
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return 0; // smth went wrong
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}
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} // namespace tools
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