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I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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i2pd/libi2pd/SSUData.cpp

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#include <stdlib.h>
#include <boost/bind.hpp>
#include "Log.h"
#include "Timestamp.h"
#include "NetDb.hpp"
#include "SSU.h"
#include "SSUData.h"
#ifdef WITH_EVENTS
#include "Event.h"
#endif
namespace i2p
{
namespace transport
{
void IncompleteMessage::AttachNextFragment (const uint8_t * fragment, size_t fragmentSize)
{
if (msg->len + fragmentSize > msg->maxLen)
{
LogPrint (eLogWarning, "SSU: I2NP message size ", msg->maxLen, " is not enough");
auto newMsg = NewI2NPMessage ();
*newMsg = *msg;
msg = newMsg;
}
if (msg->Concat (fragment, fragmentSize) < fragmentSize)
LogPrint (eLogError, "SSU: I2NP buffer overflow ", msg->maxLen);
nextFragmentNum++;
}
SSUData::SSUData (SSUSession& session):
m_Session (session), m_ResendTimer (session.GetService ()),
m_IncompleteMessagesCleanupTimer (session.GetService ()),
m_MaxPacketSize (session.IsV6 () ? SSU_V6_MAX_PACKET_SIZE : SSU_V4_MAX_PACKET_SIZE),
m_PacketSize (m_MaxPacketSize), m_LastMessageReceivedTime (0)
{
}
SSUData::~SSUData ()
{
}
void SSUData::Start ()
{
ScheduleIncompleteMessagesCleanup ();
}
void SSUData::Stop ()
{
m_ResendTimer.cancel ();
m_IncompleteMessagesCleanupTimer.cancel ();
m_IncompleteMessages.clear ();
m_SentMessages.clear ();
m_ReceivedMessages.clear ();
}
void SSUData::AdjustPacketSize (std::shared_ptr<const i2p::data::RouterInfo> remoteRouter)
{
if (!remoteRouter) return;
auto ssuAddress = remoteRouter->GetSSUAddress ();
if (ssuAddress && ssuAddress->ssu->mtu)
{
if (m_Session.IsV6 ())
m_PacketSize = ssuAddress->ssu->mtu - IPV6_HEADER_SIZE - UDP_HEADER_SIZE;
else
m_PacketSize = ssuAddress->ssu->mtu - IPV4_HEADER_SIZE - UDP_HEADER_SIZE;
if (m_PacketSize > 0)
{
// make sure packet size multiple of 16
m_PacketSize >>= 4;
m_PacketSize <<= 4;
if (m_PacketSize > m_MaxPacketSize) m_PacketSize = m_MaxPacketSize;
LogPrint (eLogDebug, "SSU: MTU=", ssuAddress->ssu->mtu, " packet size=", m_PacketSize);
}
else
{
LogPrint (eLogWarning, "SSU: Unexpected MTU ", ssuAddress->ssu->mtu);
m_PacketSize = m_MaxPacketSize;
}
}
}
void SSUData::UpdatePacketSize (const i2p::data::IdentHash& remoteIdent)
{
auto routerInfo = i2p::data::netdb.FindRouter (remoteIdent);
if (routerInfo)
AdjustPacketSize (routerInfo);
}
void SSUData::ProcessSentMessageAck (uint32_t msgID)
{
auto it = m_SentMessages.find (msgID);
if (it != m_SentMessages.end ())
{
m_SentMessages.erase (it);
if (m_SentMessages.empty ())
m_ResendTimer.cancel ();
}
}
void SSUData::ProcessAcks (uint8_t *& buf, uint8_t flag)
{
if (flag & DATA_FLAG_EXPLICIT_ACKS_INCLUDED)
{
// explicit ACKs
uint8_t numAcks =*buf;
buf++;
for (int i = 0; i < numAcks; i++)
ProcessSentMessageAck (bufbe32toh (buf+i*4));
buf += numAcks*4;
}
if (flag & DATA_FLAG_ACK_BITFIELDS_INCLUDED)
{
// explicit ACK bitfields
uint8_t numBitfields =*buf;
buf++;
for (int i = 0; i < numBitfields; i++)
{
uint32_t msgID = bufbe32toh (buf);
buf += 4; // msgID
auto it = m_SentMessages.find (msgID);
// process individual Ack bitfields
bool isNonLast = false;
int fragment = 0;
do
{
uint8_t bitfield = *buf;
isNonLast = bitfield & 0x80;
bitfield &= 0x7F; // clear MSB
if (bitfield && it != m_SentMessages.end ())
{
int numSentFragments = it->second->fragments.size ();
// process bits
uint8_t mask = 0x01;
for (int j = 0; j < 7; j++)
{
if (bitfield & mask)
{
if (fragment < numSentFragments)
it->second->fragments[fragment].reset (nullptr);
}
fragment++;
mask <<= 1;
}
}
buf++;
}
while (isNonLast);
}
}
}
void SSUData::ProcessFragments (uint8_t * buf)
{
uint8_t numFragments = *buf; // number of fragments
buf++;
for (int i = 0; i < numFragments; i++)
{
uint32_t msgID = bufbe32toh (buf); // message ID
buf += 4;
uint8_t frag[4] = {0};
memcpy (frag + 1, buf, 3);
buf += 3;
uint32_t fragmentInfo = bufbe32toh (frag); // fragment info
uint16_t fragmentSize = fragmentInfo & 0x3FFF; // bits 0 - 13
bool isLast = fragmentInfo & 0x010000; // bit 16
uint8_t fragmentNum = fragmentInfo >> 17; // bits 23 - 17
if (fragmentSize >= SSU_V4_MAX_PACKET_SIZE)
{
LogPrint (eLogError, "SSU: Fragment size ", fragmentSize, " exceeds max SSU packet size");
return;
}
// find message with msgID
auto it = m_IncompleteMessages.find (msgID);
if (it == m_IncompleteMessages.end ())
{
// create new message
auto msg = NewI2NPShortMessage ();
msg->len -= I2NP_SHORT_HEADER_SIZE;
it = m_IncompleteMessages.insert (std::make_pair (msgID,
std::unique_ptr<IncompleteMessage>(new IncompleteMessage (msg)))).first;
}
std::unique_ptr<IncompleteMessage>& incompleteMessage = it->second;
// handle current fragment
if (fragmentNum == incompleteMessage->nextFragmentNum)
{
// expected fragment
incompleteMessage->AttachNextFragment (buf, fragmentSize);
if (!isLast && !incompleteMessage->savedFragments.empty ())
{
// try saved fragments
for (auto it1 = incompleteMessage->savedFragments.begin (); it1 != incompleteMessage->savedFragments.end ();)
{
auto& savedFragment = *it1;
if (savedFragment->fragmentNum == incompleteMessage->nextFragmentNum)
{
incompleteMessage->AttachNextFragment (savedFragment->buf, savedFragment->len);
isLast = savedFragment->isLast;
incompleteMessage->savedFragments.erase (it1++);
}
else
break;
}
if (isLast)
LogPrint (eLogDebug, "SSU: Message ", msgID, " complete");
}
}
else
{
if (fragmentNum < incompleteMessage->nextFragmentNum)
// duplicate fragment
LogPrint (eLogWarning, "SSU: Duplicate fragment ", (int)fragmentNum, " of message ", msgID, ", ignored");
else
{
// missing fragment
LogPrint (eLogWarning, "SSU: Missing fragments from ", (int)incompleteMessage->nextFragmentNum, " to ", fragmentNum - 1, " of message ", msgID);
auto savedFragment = new Fragment (fragmentNum, buf, fragmentSize, isLast);
if (incompleteMessage->savedFragments.insert (std::unique_ptr<Fragment>(savedFragment)).second)
incompleteMessage->lastFragmentInsertTime = i2p::util::GetSecondsSinceEpoch ();
else
LogPrint (eLogWarning, "SSU: Fragment ", (int)fragmentNum, " of message ", msgID, " already saved");
}
isLast = false;
}
if (isLast)
{
// delete incomplete message
auto msg = incompleteMessage->msg;
incompleteMessage->msg = nullptr;
m_IncompleteMessages.erase (msgID);
// process message
SendMsgAck (msgID);
msg->FromSSU (msgID);
if (m_Session.GetState () == eSessionStateEstablished)
{
if (!m_ReceivedMessages.count (msgID))
{
m_ReceivedMessages.insert (msgID);
m_LastMessageReceivedTime = i2p::util::GetSecondsSinceEpoch ();
if (!msg->IsExpired ())
{
#ifdef WITH_EVENTS
QueueIntEvent("transport.recvmsg", m_Session.GetIdentHashBase64(), 1);
#endif
m_Handler.PutNextMessage (msg);
}
else
LogPrint (eLogDebug, "SSU: message expired");
}
else
LogPrint (eLogWarning, "SSU: Message ", msgID, " already received");
}
else
{
// we expect DeliveryStatus
if (msg->GetTypeID () == eI2NPDeliveryStatus)
{
LogPrint (eLogDebug, "SSU: session established");
m_Session.Established ();
}
else
LogPrint (eLogError, "SSU: unexpected message ", (int)msg->GetTypeID ());
}
}
else
SendFragmentAck (msgID, fragmentNum);
buf += fragmentSize;
}
}
void SSUData::FlushReceivedMessage ()
{
m_Handler.Flush ();
}
void SSUData::ProcessMessage (uint8_t * buf, size_t len)
{
//uint8_t * start = buf;
uint8_t flag = *buf;
buf++;
LogPrint (eLogDebug, "SSU: Process data, flags=", (int)flag, ", len=", len);
// process acks if presented
if (flag & (DATA_FLAG_ACK_BITFIELDS_INCLUDED | DATA_FLAG_EXPLICIT_ACKS_INCLUDED))
ProcessAcks (buf, flag);
// extended data if presented
if (flag & DATA_FLAG_EXTENDED_DATA_INCLUDED)
{
uint8_t extendedDataSize = *buf;
buf++; // size
LogPrint (eLogDebug, "SSU: extended data of ", extendedDataSize, " bytes present");
buf += extendedDataSize;
}
// process data
ProcessFragments (buf);
}
void SSUData::Send (std::shared_ptr<i2p::I2NPMessage> msg)
{
uint32_t msgID = msg->ToSSU ();
if (m_SentMessages.count (msgID) > 0)
{
LogPrint (eLogWarning, "SSU: message ", msgID, " already sent");
return;
}
if (m_SentMessages.empty ()) // schedule resend at first message only
ScheduleResend ();
auto ret = m_SentMessages.insert (std::make_pair (msgID, std::unique_ptr<SentMessage>(new SentMessage)));
std::unique_ptr<SentMessage>& sentMessage = ret.first->second;
if (ret.second)
{
sentMessage->nextResendTime = i2p::util::GetSecondsSinceEpoch () + RESEND_INTERVAL;
sentMessage->numResends = 0;
}
auto& fragments = sentMessage->fragments;
size_t payloadSize = m_PacketSize - sizeof (SSUHeader) - 9; // 9 = flag + #frg(1) + messageID(4) + frag info (3)
size_t len = msg->GetLength ();
uint8_t * msgBuf = msg->GetSSUHeader ();
uint32_t fragmentNum = 0;
while (len > 0)
{
Fragment * fragment = new Fragment;
fragment->fragmentNum = fragmentNum;
uint8_t * buf = fragment->buf;
uint8_t * payload = buf + sizeof (SSUHeader);
*payload = DATA_FLAG_WANT_REPLY; // for compatibility
payload++;
*payload = 1; // always 1 message fragment per message
payload++;
htobe32buf (payload, msgID);
payload += 4;
bool isLast = (len <= payloadSize);
size_t size = isLast ? len : payloadSize;
uint32_t fragmentInfo = (fragmentNum << 17);
if (isLast)
fragmentInfo |= 0x010000;
fragmentInfo |= size;
fragmentInfo = htobe32 (fragmentInfo);
memcpy (payload, (uint8_t *)(&fragmentInfo) + 1, 3);
payload += 3;
memcpy (payload, msgBuf, size);
size += payload - buf;
if (size & 0x0F) // make sure 16 bytes boundary
size = ((size >> 4) + 1) << 4; // (/16 + 1)*16
fragment->len = size;
fragments.push_back (std::unique_ptr<Fragment> (fragment));
// encrypt message with session key
m_Session.FillHeaderAndEncrypt (PAYLOAD_TYPE_DATA, buf, size);
try
{
m_Session.Send (buf, size);
}
catch (boost::system::system_error& ec)
{
LogPrint (eLogWarning, "SSU: Can't send data fragment ", ec.what ());
}
if (!isLast)
{
len -= payloadSize;
msgBuf += payloadSize;
}
else
len = 0;
fragmentNum++;
}
}
void SSUData::SendMsgAck (uint32_t msgID)
{
uint8_t buf[48 + 18] = {0}; // actual length is 44 = 37 + 7 but pad it to multiple of 16
uint8_t * payload = buf + sizeof (SSUHeader);
*payload = DATA_FLAG_EXPLICIT_ACKS_INCLUDED; // flag
payload++;
*payload = 1; // number of ACKs
payload++;
htobe32buf (payload, msgID); // msgID
payload += 4;
*payload = 0; // number of fragments
// encrypt message with session key
m_Session.FillHeaderAndEncrypt (PAYLOAD_TYPE_DATA, buf, 48);
m_Session.Send (buf, 48);
}
void SSUData::SendFragmentAck (uint32_t msgID, int fragmentNum)
{
if (fragmentNum > 64)
{
LogPrint (eLogWarning, "SSU: Fragment number ", fragmentNum, " exceeds 64");
return;
}
uint8_t buf[64 + 18] = {0};
uint8_t * payload = buf + sizeof (SSUHeader);
*payload = DATA_FLAG_ACK_BITFIELDS_INCLUDED; // flag
payload++;
*payload = 1; // number of ACK bitfields
payload++;
// one ack
*(uint32_t *)(payload) = htobe32 (msgID); // msgID
payload += 4;
div_t d = div (fragmentNum, 7);
memset (payload, 0x80, d.quot); // 0x80 means non-last
payload += d.quot;
*payload = 0x01 << d.rem; // set corresponding bit
payload++;
*payload = 0; // number of fragments
size_t len = d.quot < 4 ? 48 : 64; // 48 = 37 + 7 + 4 (3+1)
// encrypt message with session key
m_Session.FillHeaderAndEncrypt (PAYLOAD_TYPE_DATA, buf, len);
m_Session.Send (buf, len);
}
void SSUData::ScheduleResend()
{
m_ResendTimer.cancel ();
m_ResendTimer.expires_from_now (boost::posix_time::seconds(RESEND_INTERVAL));
auto s = m_Session.shared_from_this();
m_ResendTimer.async_wait ([s](const boost::system::error_code& ecode)
{ s->m_Data.HandleResendTimer (ecode); });
}
void SSUData::HandleResendTimer (const boost::system::error_code& ecode)
{
if (ecode != boost::asio::error::operation_aborted)
{
uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
int numResent = 0;
for (auto it = m_SentMessages.begin (); it != m_SentMessages.end ();)
{
if (ts >= it->second->nextResendTime)
{
if (it->second->numResends < MAX_NUM_RESENDS)
{
for (auto& f: it->second->fragments)
if (f)
{
try
{
m_Session.Send (f->buf, f->len); // resend
numResent++;
}
catch (boost::system::system_error& ec)
{
LogPrint (eLogWarning, "SSU: Can't resend data fragment ", ec.what ());
}
}
it->second->numResends++;
it->second->nextResendTime += it->second->numResends*RESEND_INTERVAL;
++it;
}
else
{
LogPrint (eLogInfo, "SSU: message has not been ACKed after ", MAX_NUM_RESENDS, " attempts, deleted");
it = m_SentMessages.erase (it);
}
}
else
++it;
}
if (m_SentMessages.empty ()) return; // nothing to resend
if (numResent < MAX_OUTGOING_WINDOW_SIZE)
ScheduleResend ();
else
{
LogPrint (eLogError, "SSU: resend window exceeds max size. Session terminated");
m_Session.Close ();
}
}
}
void SSUData::ScheduleIncompleteMessagesCleanup ()
{
m_IncompleteMessagesCleanupTimer.cancel ();
m_IncompleteMessagesCleanupTimer.expires_from_now (boost::posix_time::seconds(INCOMPLETE_MESSAGES_CLEANUP_TIMEOUT));
auto s = m_Session.shared_from_this();
m_IncompleteMessagesCleanupTimer.async_wait ([s](const boost::system::error_code& ecode)
{ s->m_Data.HandleIncompleteMessagesCleanupTimer (ecode); });
}
void SSUData::HandleIncompleteMessagesCleanupTimer (const boost::system::error_code& ecode)
{
if (ecode != boost::asio::error::operation_aborted)
{
uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
for (auto it = m_IncompleteMessages.begin (); it != m_IncompleteMessages.end ();)
{
if (ts > it->second->lastFragmentInsertTime + INCOMPLETE_MESSAGES_CLEANUP_TIMEOUT)
{
LogPrint (eLogWarning, "SSU: message ", it->first, " was not completed in ", INCOMPLETE_MESSAGES_CLEANUP_TIMEOUT, " seconds, deleted");
it = m_IncompleteMessages.erase (it);
}
else
++it;
}
// decay
if (m_ReceivedMessages.size () > MAX_NUM_RECEIVED_MESSAGES ||
i2p::util::GetSecondsSinceEpoch () > m_LastMessageReceivedTime + DECAY_INTERVAL)
m_ReceivedMessages.clear ();
ScheduleIncompleteMessagesCleanup ();
}
}
}
}