NTP request

Timestamp.cpp

@@ -1,3 +1,7 @@
+#include <inttypes.h>
+#include <string.h>
+#include <boost/asio.hpp>
+#include "I2PEndian.h"
 #include "Timestamp.h"
 
 namespace i2p
@@ -5,6 +9,42 @@ namespace i2p
 namespace util
 {
 	std::chrono::system_clock::duration g_TimeOffset = std::chrono::system_clock::duration::zero ();
+
+	void SyncTimeWithNTP (const std::string& address)
+	{
+		boost::asio::io_service service;
+		boost::asio::ip::udp::resolver::query query (boost::asio::ip::udp::v4 (), address, "ntp");
+		boost::system::error_code ec;
+		auto it = boost::asio::ip::udp::resolver (service).resolve (query, ec);
+		if (!ec && it != boost::asio::ip::udp::resolver::iterator())
+		{
+			auto ep = (*it).endpoint (); // take first one
+			boost::asio::ip::udp::socket socket (service);
+			socket.open (boost::asio::ip::udp::v4 (), ec);
+			if (!ec)
+			{
+				uint8_t request[48];// 48 bytes NTP request
+				memset (request, 0, 48);
+				request[0] = 0x80; // client mode, version 0
+				uint8_t * response = new uint8_t[1500]; // MTU
+				size_t len = 0;
+				try
+				{
+					socket.send_to (boost::asio::buffer (request, 48), ep);
+					len = socket.receive_from (boost::asio::buffer (response, 1500), ep);
+				}
+				catch (std::exception& e)
+				{
+				}	
+				if (len >= 8)
+				{
+					uint32_t ts = bufbe32toh (response + 4);
+					if (ts > 2208988800U) ts -= 2208988800U; // 1/1/1970 from 1/1/1900
+				}	
+				delete[] response;
+			}
+		}
+	}	
 }
 }