I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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#include "Log.h"
#include "SSU.h"
#include "SSUData.h"
namespace i2p
{
namespace ssu
{
SSUData::SSUData (SSUSession& session):
m_Session (session)
{
}
SSUData::~SSUData ()
{
for (auto it: m_IncomleteMessages)
if (it.second)
{
DeleteI2NPMessage (it.second->msg);
delete it.second;
}
}
void SSUData::ProcessMessage (uint8_t * buf, size_t len)
{
//uint8_t * start = buf;
uint8_t flag = *buf;
buf++;
LogPrint ("Process SSU data flags=", (int)flag);
if (flag & DATA_FLAG_EXPLICIT_ACKS_INCLUDED)
{
// explicit ACKs
uint8_t numAcks =*buf;
buf++;
// TODO: process ACKs
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++)
{
buf += 4; // msgID
// TODO: process ACH bitfields
while (*buf & 0x80) // not last
buf++;
buf++; // last byte
}
}
uint8_t numFragments = *buf; // number of fragments
buf++;
for (int i = 0; i < numFragments; i++)
{
uint32_t msgID = be32toh (*(uint32_t *)buf); // message ID
buf += 4;
uint8_t frag[4];
frag[0] = 0;
memcpy (frag + 1, buf, 3);
buf += 3;
uint32_t fragmentInfo = be32toh (*(uint32_t *)frag); // fragment info
uint16_t fragmentSize = fragmentInfo & 0x1FFF; // bits 0 - 13
bool isLast = fragmentInfo & 0x010000; // bit 16
uint8_t fragmentNum = fragmentInfo >> 17; // bits 23 - 17
LogPrint ("SSU data fragment ", (int)fragmentNum, " of message ", msgID, " size=", (int)fragmentSize, isLast ? " last" : " non-last");
I2NPMessage * msg = nullptr;
if (fragmentNum > 0) // follow-up fragment
{
auto it = m_IncomleteMessages.find (msgID);
if (it != m_IncomleteMessages.end ())
{
if (fragmentNum == it->second->nextFragmentNum)
{
// expected fragment
msg = it->second->msg;
memcpy (msg->buf + msg->len, buf, fragmentSize);
msg->len += fragmentSize;
it->second->nextFragmentNum++;
}
else if (fragmentNum < it->second->nextFragmentNum)
// duplicate fragment
LogPrint ("Duplicate fragment ", fragmentNum, " of message ", msgID, ". Ignored");
else
{
// missing fragment
LogPrint ("Missing fragments from ", it->second->nextFragmentNum, " to ", fragmentNum - 1, " of message ", msgID);
//TODO
}
if (isLast)
{
if (!msg)
DeleteI2NPMessage (it->second->msg);
delete it->second;
m_IncomleteMessages.erase (it);
}
}
else
// TODO:
LogPrint ("Unexpected follow-on fragment ", fragmentNum, " of message ", msgID);
}
else // first fragment
{
msg = NewI2NPMessage ();
memcpy (msg->GetSSUHeader (), buf, fragmentSize);
msg->len += fragmentSize - sizeof (I2NPHeaderShort);
}
if (msg)
{
if (!fragmentNum && !isLast)
m_IncomleteMessages[msgID] = new IncompleteMessage (msg);
if (isLast)
{
SendMsgAck (msgID);
msg->FromSSU (msgID);
if (m_Session.GetState () == eSessionStateEstablished)
i2p::HandleI2NPMessage (msg);
else
{
// we expect DeliveryStatus
if (msg->GetHeader ()->typeID == eI2NPDeliveryStatus)
{
LogPrint ("SSU session established");
m_Session.Established ();
}
else
LogPrint ("SSU unexpected message ", (int)msg->GetHeader ()->typeID);
DeleteI2NPMessage (msg);
}
}
}
buf += fragmentSize;
}
}
void SSUData::Send (i2p::I2NPMessage * msg)
{
uint32_t msgID = htobe32 (msg->ToSSU ());
size_t payloadSize = SSU_MTU - 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)
{
uint8_t buf[SSU_MTU + 18], * payload = buf + sizeof (SSUHeader);
*payload = DATA_FLAG_WANT_REPLY; // for compatibility
payload++;
*payload = 1; // always 1 message fragment per message
payload++;
*(uint32_t *)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
// encrypt message with session key
m_Session.FillHeaderAndEncrypt (PAYLOAD_TYPE_DATA, buf, size);
m_Session.Send (buf, size);
if (!isLast)
{
len -= payloadSize;
msgBuf += payloadSize;
}
else
len = 0;
fragmentNum++;
}
DeleteI2NPMessage (msg);
}
void SSUData::SendMsgAck (uint32_t msgID)
{
uint8_t buf[48 + 18]; // 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++;
*(uint32_t *)(payload) = htobe32 (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);
}
}
}