An SNTP client implementation. About 95% complete right now.

2025-12-06 17:27:55 +00:00 · 2012-08-04 21:33:05 -07:00
parent 78f415f386
commit ee01b55874
7 changed files with 260 additions and 1 deletions
--- a/src/SNTPClient.cpp
+++ b/src/SNTPClient.cpp
@@ -0,0 +1,180 @@
+#include "SNTPClient.h"
+
+#include <boost/bind.hpp>
+#include <boost/make_shared.hpp>
+
+#include "utils.h"
+#include "Log.h"
+
+static uint8_t SNTPQueryData[48] = {
+	0x1B,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+};
+
+SNTPClient::SNTPClient(boost::asio::io_service& service) :
+		mIOService(service), mSocket(service), mTimer(service), mResolver(service),
+		mOffset(0), mLastOffsetUpdate((time_t) -1), mReceiveBuffer(256)
+{
+	mSocket.open(boost::asio::ip::udp::v4());
+	mSocket.async_receive_from(boost::asio::buffer(mReceiveBuffer, 256), mReceiveEndpoint,
+		boost::bind(&SNTPClient::receivePacket, this, boost::asio::placeholders::error,
+			boost::asio::placeholders::bytes_transferred));
+	
+	mTimer.expires_from_now(boost::posix_time::seconds(1));
+	mTimer.async_wait(boost::bind(&SNTPClient::timerEntry, this, boost::asio::placeholders::error));
+}
+
+void SNTPClient::resolveComplete(const boost::system::error_code& error, boost::asio::ip::udp::resolver::iterator it)
+{
+	if (!error)
+	{
+		boost::asio::ip::udp::resolver::iterator sel = it;
+		int i = 1;
+		while (++it != boost::asio::ip::udp::resolver::iterator())
+			if ((rand() % ++i) == 0)
+				sel = it;
+		if (sel != boost::asio::ip::udp::resolver::iterator())
+		{
+			boost::mutex::scoped_lock sl(mLock);
+			SNTPQuery& query = mQueries[*sel];
+			time_t now = time(NULL);
+			if ((query.mLocalTimeSent == now) || ((query.mLocalTimeSent + 1) == now))
+			{
+				Log(lsINFO) << "SNTP: Redundant query suppressed";
+				return;
+			}
+			query.mReceivedReply = false;
+			query.mLocalTimeSent = now;
+			mSocket.async_send_to(boost::asio::buffer(SNTPQueryData, 256), *sel,
+				boost::bind(&SNTPClient::sendComplete, this,
+					boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
+		}
+	}
+}
+
+void SNTPClient::receivePacket(const boost::system::error_code& error, std::size_t bytes_xferd)
+{
+	if (!error)
+	{
+		boost::mutex::scoped_lock sl(mLock);
+		Log(lsINFO) << "SNTP: Packet from " << mReceiveEndpoint;
+		std::map<boost::asio::ip::udp::endpoint, SNTPQuery>::iterator query = mQueries.find(mReceiveEndpoint);
+		if (query == mQueries.end())
+			Log(lsINFO) << "SNTP: Reply found without matching query";
+		else if (query->second.mReceivedReply)
+			Log(lsINFO) << "SNTP: Duplicate response to query";
+		else
+		{
+			query->second.mReceivedReply = true;
+			if (time(NULL) > (query->second.mLocalTimeSent + 1))
+				Log(lsINFO) << "SNTP: Late response";
+			else
+				if (bytes_xferd < 48)
+					Log(lsINFO) << "SNTP: Short reply (" << bytes_xferd << ") " << mReceiveBuffer.size();
+				else
+					processReply();
+		}
+	}
+
+	mSocket.async_receive_from(boost::asio::buffer(mReceiveBuffer, 256), mReceiveEndpoint,
+		boost::bind(&SNTPClient::receivePacket, this, boost::asio::placeholders::error,
+			boost::asio::placeholders::bytes_transferred));
+}
+
+void SNTPClient::sendComplete(const boost::system::error_code& error, std::size_t)
+{
+	if (error)
+		Log(lsINFO) << "SNTP: Send error";
+}
+
+void SNTPClient::processReply()
+{
+	assert(mReceiveBuffer.size() >= 48);
+	uint32 *recvBuffer = reinterpret_cast<uint32*>(&mReceiveBuffer.front());
+
+	unsigned info = ntohl(recvBuffer[0]);
+	int64_t timev = ntohl(recvBuffer[8]);
+	unsigned stratum = (info >> 16) & 0xff;
+
+	if ((info >> 30) == 3)
+	{
+		Log(lsINFO) << "SNTP: Alarm condition";
+		return;
+	}
+	if ((stratum == 0) || (stratum > 14))
+	{
+		Log(lsINFO) << "SNTP: Unreasonable stratum";
+		return;
+	}
+
+	timev -= time(NULL);
+	timev -= 0x83AA7E80ULL;
+	Log(lsINFO) << "SNTP: Offset is " << timev;	
+
+	// WRITEME
+}
+
+void SNTPClient::timerEntry(const boost::system::error_code& error)
+{
+	if (!error)
+	{
+		doQuery();
+		mTimer.expires_from_now(boost::posix_time::seconds(10));
+		mTimer.async_wait(boost::bind(&SNTPClient::timerEntry, this, boost::asio::placeholders::error));
+	}
+}
+
+void SNTPClient::addServer(const std::string& server)
+{
+	boost::mutex::scoped_lock sl(mLock);
+	mServers.push_back(std::make_pair(server, (time_t) -1));
+}
+
+void SNTPClient::init(const std::vector<std::string>& servers)
+{
+	std::vector<std::string>::const_iterator it = servers.begin();
+	if (it == servers.end())
+	{
+		Log(lsINFO) << "SNTP: no server specified";
+		return;
+	}
+	do
+		addServer(*it++);
+	while (it != servers.end());
+	queryAll();
+}
+
+void SNTPClient::queryAll()
+{
+	while(doQuery())
+		nothing();
+}
+
+bool SNTPClient::doQuery()
+{
+	boost::mutex::scoped_lock sl(mLock);
+	std::vector< std::pair<std::string, time_t> >::iterator best = mServers.end();
+	for (std::vector< std::pair<std::string, time_t> >::iterator it = mServers.begin(), end = best;
+			it != end; ++it)
+		if ((best == end) || (it->second == (time_t) -1) || (it->second < best->second))
+			best = it;
+	if (best == mServers.end())
+	{
+		Log(lsINFO) << "SNTP: No server to query";
+		return false;
+	}
+	time_t now = time(NULL);
+	if ((best->second == now) || (best->second == (now - 1)))
+	{
+		Log(lsINFO) << "SNTP: All servers recently queried";
+		return false;
+	}
+	best->second = now;
+
+	boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), best->first, "ntp");
+	mResolver.async_resolve(query,
+		boost::bind(&SNTPClient::resolveComplete, this,
+		boost::asio::placeholders::error, boost::asio::placeholders::iterator));
+	Log(lsINFO) << "SNTP: Resolve pending for " << best->first;
+	return true;
+}