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net: Consistent checksum handling

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In principle, the checksums of P2P packets are simply 4-byte blobs which
are the first four bytes of SHA256(SHA256(payload)).

Currently they are handled as little-endian 32-bit integers half of the
time, as blobs the other half, sometimes copying the one to the other,
resulting in somewhat confused code.

This PR changes the handling to be consistent both at packet creation
and receiving, making it (I think) easier to understand.
This commit is contained in:
Wladimir J. van der Laan 2016-09-27 14:05:24 +02:00
parent 920ca1f0bf
commit 41e58faf04
4 changed files with 11 additions and 12 deletions
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9
src/main.cpp
View file

@ -6253,11 +6253,12 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman)
// Checksum
CDataStream& vRecv = msg.vRecv;
uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
unsigned int nChecksum = ReadLE32((unsigned char*)&hash);
if (nChecksum != hdr.nChecksum)
if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
{
LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR nChecksum=%08x hdr.nChecksum=%08x\n", __func__,
SanitizeString(strCommand), nMessageSize, nChecksum, hdr.nChecksum);
LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
SanitizeString(strCommand), nMessageSize,
HexStr(hash.begin(), hash.begin()+CMessageHeader::CHECKSUM_SIZE),
HexStr(hdr.pchChecksum, hdr.pchChecksum+CMessageHeader::CHECKSUM_SIZE));
continue;
}

6
src/net.cpp
View file

@ -2661,10 +2661,8 @@ void CNode::EndMessage(const char* pszCommand) UNLOCK_FUNCTION(cs_vSend)
// Set the checksum
uint256 hash = Hash(ssSend.begin() + CMessageHeader::HEADER_SIZE, ssSend.end());
unsigned int nChecksum = 0;
memcpy(&nChecksum, &hash, sizeof(nChecksum));
assert(ssSend.size () >= CMessageHeader::CHECKSUM_OFFSET + sizeof(nChecksum));
memcpy((char*)&ssSend[CMessageHeader::CHECKSUM_OFFSET], &nChecksum, sizeof(nChecksum));
assert(ssSend.size () >= CMessageHeader::CHECKSUM_OFFSET + CMessageHeader::CHECKSUM_SIZE);
memcpy((char*)&ssSend[CMessageHeader::CHECKSUM_OFFSET], hash.begin(), CMessageHeader::CHECKSUM_SIZE);
LogPrint("net", "(%d bytes) peer=%d\n", nSize, id);

4
src/protocol.cpp
View file

@ -79,7 +79,7 @@ CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn)
memcpy(pchMessageStart, pchMessageStartIn, MESSAGE_START_SIZE);
memset(pchCommand, 0, sizeof(pchCommand));
nMessageSize = -1;
nChecksum = 0;
memset(pchChecksum, 0, CHECKSUM_SIZE);
}
CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn, const char* pszCommand, unsigned int nMessageSizeIn)
@ -88,7 +88,7 @@ CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn, const
memset(pchCommand, 0, sizeof(pchCommand));
strncpy(pchCommand, pszCommand, COMMAND_SIZE);
nMessageSize = nMessageSizeIn;
nChecksum = 0;
memset(pchChecksum, 0, CHECKSUM_SIZE);
}
std::string CMessageHeader::GetCommand() const

4
src/protocol.h
View file

@ -45,7 +45,7 @@ public:
READWRITE(FLATDATA(pchMessageStart));
READWRITE(FLATDATA(pchCommand));
READWRITE(nMessageSize);
READWRITE(nChecksum);
READWRITE(FLATDATA(pchChecksum));
}
// TODO: make private (improves encapsulation)
@ -62,7 +62,7 @@ public:
char pchMessageStart[MESSAGE_START_SIZE];
char pchCommand[COMMAND_SIZE];
unsigned int nMessageSize;
unsigned int nChecksum;
uint8_t pchChecksum[CHECKSUM_SIZE];
};
/**