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Improve handling of unconnecting headers

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When processing a headers message that looks like a block announcement,
send peer a getheaders if the headers message won't connect.

Apply DoS points after too many consecutive unconnecting headers messages.
This commit is contained in:
Suhas Daftuar 2016-07-06 21:18:38 -04:00
parent b978701ba1
commit 96fa95361f
2 changed files with 40 additions and 1 deletions
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38
src/main.cpp
View file

@ -276,6 +276,8 @@ struct CNodeState {
CBlockIndex *pindexLastCommonBlock;
//! The best header we have sent our peer.
CBlockIndex *pindexBestHeaderSent;
//! Length of current-streak of unconnecting headers announcements
int nUnconnectingHeaders;
//! Whether we've started headers synchronization with this peer.
bool fSyncStarted;
//! Since when we're stalling block download progress (in microseconds), or 0.
@ -304,6 +306,7 @@ struct CNodeState {
hashLastUnknownBlock.SetNull();
pindexLastCommonBlock = NULL;
pindexBestHeaderSent = NULL;
nUnconnectingHeaders = 0;
fSyncStarted = false;
nStallingSince = 0;
nDownloadingSince = 0;
@ -5773,6 +5776,35 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
return true;
}
CNodeState *nodestate = State(pfrom->GetId());
// If this looks like it could be a block announcement (nCount <
// MAX_BLOCKS_TO_ANNOUNCE), use special logic for handling headers that
// don't connect:
// - Send a getheaders message in response to try to connect the chain.
// - The peer can send up to MAX_UNCONNECTING_HEADERS in a row that
// don't connect before giving DoS points
// - Once a headers message is received that is valid and does connect,
// nUnconnectingHeaders gets reset back to 0.
if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
nodestate->nUnconnectingHeaders++;
pfrom->PushMessage(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256());
LogPrint("net", "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
headers[0].GetHash().ToString(),
headers[0].hashPrevBlock.ToString(),
pindexBestHeader->nHeight,
pfrom->id, nodestate->nUnconnectingHeaders);
// Set hashLastUnknownBlock for this peer, so that if we
// eventually get the headers - even from a different peer -
// we can use this peer to download.
UpdateBlockAvailability(pfrom->GetId(), headers.back().GetHash());
if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
Misbehaving(pfrom->GetId(), 20);
}
return true;
}
CBlockIndex *pindexLast = NULL;
BOOST_FOREACH(const CBlockHeader& header, headers) {
CValidationState state;
@ -5790,6 +5822,11 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
}
}
if (nodestate->nUnconnectingHeaders > 0) {
LogPrint("net", "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->id, nodestate->nUnconnectingHeaders);
}
nodestate->nUnconnectingHeaders = 0;
assert(pindexLast);
UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
@ -5802,7 +5839,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
}
bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
CNodeState *nodestate = State(pfrom->GetId());
// If this set of headers is valid and ends in a block with at least as
// much work as our tip, download as much as possible.
if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {

3
src/main.h
View file

@ -138,6 +138,9 @@ static const bool DEFAULT_FEEFILTER = true;
/** Maximum number of headers to announce when relaying blocks with headers message.*/
static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
/** Maximum number of unconnecting headers announcements before DoS score */
static const int MAX_UNCONNECTING_HEADERS = 10;
static const bool DEFAULT_PEERBLOOMFILTERS = true;
struct BlockHasher