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authorSuhas Daftuar <sdaftuar@chaincode.com>2016-07-06 21:18:38 -0400
committerSuhas Daftuar <sdaftuar@chaincode.com>2016-07-12 13:12:40 -0400
commit96fa95361f68dd8169fa60e73290afae47445299 (patch)
tree0cbfc0a694054e7cda668148f2d5508109f5ff3e
parentb978701ba1822140452d35f037ce776fdcba0175 (diff)
Improve handling of unconnecting headers
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.
-rw-r--r--src/main.cpp38
-rw-r--r--src/main.h3
2 files changed, 40 insertions, 1 deletions
diff --git a/src/main.cpp b/src/main.cpp
index b86bbda1b8..dd71ee5510 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -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) {
diff --git a/src/main.h b/src/main.h
index 7ea570d859..65ae2488f9 100644
--- a/src/main.h
+++ b/src/main.h
@@ -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