adjust clock from SSU SessionCreated is time difference exceeds 15 seconds

libi2pd/Config.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2020, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -272,8 +272,9 @@ namespace config {
 				"1.pool.ntp.org,"
 				"2.pool.ntp.org,"
 				"3.pool.ntp.org"
-			),                                                             "Comma separated list of NTCP servers")
+			),                                                             "Comma separated list of NTP servers")
 			("nettime.ntpsyncinterval", value<int>()->default_value(72),   "NTP sync interval in hours (default: 72)")
+			("nettime.frompeers", value<bool>()->default_value(true),      "Sync clock from transport peers (default: enabled)")
 		;
 
 		options_description persist("Network information persisting options");

libi2pd/SSU.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -11,8 +11,9 @@
 #include "Timestamp.h"
 #include "RouterContext.h"
 #include "NetDb.hpp"
-#include "SSU.h"
+#include "Config.h"
 #include "util.h"
+#include "SSU.h"
 
 #ifdef __linux__
 	#include <linux/in6.h>
@@ -33,7 +34,8 @@ namespace transport
 		m_Endpoint (boost::asio::ip::udp::v4 (), port), m_EndpointV6 (boost::asio::ip::udp::v6 (), port),
 		m_Socket (m_ReceiversService), m_SocketV6 (m_ReceiversServiceV6),
 		m_IntroducersUpdateTimer (m_Service), m_IntroducersUpdateTimerV6 (m_Service),
-		m_PeerTestsCleanupTimer (m_Service), m_TerminationTimer (m_Service), m_TerminationTimerV6 (m_Service)
+		m_PeerTestsCleanupTimer (m_Service), m_TerminationTimer (m_Service), m_TerminationTimerV6 (m_Service),
+		m_IsSyncClockFromPeers (true)
 	{
 	}
 
@@ -90,6 +92,7 @@ namespace transport
 
 	void SSUServer::Start ()
 	{
+		i2p::config::GetOption("nettime.frompeers", m_IsSyncClockFromPeers);
 		m_IsRunning = true;
 		m_Thread = new std::thread (std::bind (&SSUServer::Run, this));
 		if (context.SupportsV4 ())

libi2pd/SSU.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -69,6 +69,7 @@ namespace transport
 			i2p::util::MemoryPool<SentMessage>& GetSentMessagesPool () { return m_SentMessagesPool; };
 
 			uint16_t GetPort () const { return m_Endpoint.port (); };
+			bool IsSyncClockFromPeers () const { return m_IsSyncClockFromPeers; };
 			void SetLocalAddress (const boost::asio::ip::address& localAddress);
 
 			void Send (const uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& to);
@@ -136,6 +137,7 @@ namespace transport
 			boost::asio::ip::udp::socket m_Socket, m_SocketV6;
 			boost::asio::deadline_timer m_IntroducersUpdateTimer, m_IntroducersUpdateTimerV6,
 				m_PeerTestsCleanupTimer, m_TerminationTimer, m_TerminationTimerV6;
+			bool m_IsSyncClockFromPeers;
 			std::list<boost::asio::ip::udp::endpoint> m_Introducers, m_IntroducersV6; // introducers we are connected to
 			std::map<boost::asio::ip::udp::endpoint, std::shared_ptr<SSUSession> > m_Sessions, m_SessionsV6;
 			std::map<uint32_t, std::shared_ptr<SSUSession> > m_Relays; // we are introducer

libi2pd/SSUSession.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -274,16 +274,7 @@ namespace transport
 		s.Insert (payload, 8); // relayTag and signed on time
 		m_RelayTag = bufbe32toh (payload);
 		payload += 4; // relayTag
-		if (ourIP.is_v4 () && i2p::context.GetStatus () == eRouterStatusTesting)
-		{
-			auto ts = i2p::util::GetSecondsSinceEpoch ();
 		uint32_t signedOnTime = bufbe32toh(payload);
-			if (signedOnTime < ts - SSU_CLOCK_SKEW || signedOnTime > ts + SSU_CLOCK_SKEW)
-			{
-				LogPrint (eLogError, "SSU: Clock skew detected ", (int)ts - signedOnTime, ". Check your clock");
-				i2p::context.SetError (eRouterErrorClockSkew);
-			}
-		}
 		payload += 4; // signed on time
 		// decrypt signature
 		size_t signatureLen = m_RemoteIdentity->GetSignatureLen ();
@@ -295,6 +286,24 @@ namespace transport
 		// verify signature
 		if (s.Verify (m_RemoteIdentity, payload))
 		{
+			if (ourIP.is_v4 () && i2p::context.GetStatus () == eRouterStatusTesting)
+			{
+				auto ts = i2p::util::GetSecondsSinceEpoch ();
+				int offset = (int)ts - signedOnTime;
+				if (m_Server.IsSyncClockFromPeers ())
+				{
+					if (std::abs (offset) > SSU_CLOCK_THRESHOLD)
+					{
+						LogPrint (eLogWarning, "SSU: Clock adjusted by ", -offset, " seconds");
+						i2p::util::AdjustTimeOffset (-offset);
+					}	
+				}	
+				else if (std::abs (offset) > SSU_CLOCK_SKEW)
+				{
+					LogPrint (eLogError, "SSU: Clock skew detected ", offset, ". Check your clock");
+					i2p::context.SetError (eRouterErrorClockSkew);
+				}
+			}
 			LogPrint (eLogInfo, "SSU: Our external address is ", ourIP.to_string (), ":", ourPort);
 			if (!i2p::util::net::IsInReservedRange (ourIP))
 			{

libi2pd/SSUSession.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -36,6 +36,7 @@ namespace transport
 	const int SSU_CONNECT_TIMEOUT = 5; // 5 seconds
 	const int SSU_TERMINATION_TIMEOUT = 330; // 5.5 minutes
 	const int SSU_CLOCK_SKEW = 60; // in seconds
+	const int SSU_CLOCK_THRESHOLD = 15; // in seconds, if more we should adjust
 	const size_t SSU_MAX_I2NP_MESSAGE_SIZE = 32768;
 
 	// payload types (4 bits)

libi2pd/Timestamp.cpp

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2021, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -250,5 +250,10 @@ namespace util
 		sprintf(date, "%04i%02i%02i", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
 #endif
 	}
+
+	void AdjustTimeOffset (int64_t offset)
+	{
+		g_TimeOffset += offset;
+	}	
 }
 }

libi2pd/Timestamp.h

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2013-2020, The PurpleI2P Project
+* Copyright (c) 2013-2022, The PurpleI2P Project
 *
 * This file is part of Purple i2pd project and licensed under BSD3
 *
@@ -26,6 +26,7 @@ namespace util
 
 	void GetCurrentDate (char * date); // returns date as YYYYMMDD string, 9 bytes
 	void GetDateString (uint64_t timestamp, char * date); // timestap is seconds since epoch, returns date as YYYYMMDD string, 9 bytes
+	void AdjustTimeOffset (int64_t offset); // in seconds from current
 	
 	class NTPTimeSync
 	{