diff options
Diffstat (limited to 'src/net_processing.cpp')
| -rw-r--r-- | src/net_processing.cpp | 471 |
1 files changed, 332 insertions, 139 deletions
diff --git a/src/net_processing.cpp b/src/net_processing.cpp index 6c26cd4cee..92b7a75f73 100644 --- a/src/net_processing.cpp +++ b/src/net_processing.cpp @@ -124,6 +124,9 @@ namespace { /** Number of peers from which we're downloading blocks. */ int nPeersWithValidatedDownloads = 0; + /** Number of outbound peers with m_chain_sync.m_protect. */ + int g_outbound_peers_with_protect_from_disconnect = 0; + /** Relay map, protected by cs_main. */ typedef std::map<uint256, CTransactionRef> MapRelay; MapRelay mapRelay; @@ -201,6 +204,33 @@ struct CNodeState { */ bool fSupportsDesiredCmpctVersion; + /** State used to enforce CHAIN_SYNC_TIMEOUT + * Only in effect for outbound, non-manual connections, with + * m_protect == false + * Algorithm: if a peer's best known block has less work than our tip, + * set a timeout CHAIN_SYNC_TIMEOUT seconds in the future: + * - If at timeout their best known block now has more work than our tip + * when the timeout was set, then either reset the timeout or clear it + * (after comparing against our current tip's work) + * - If at timeout their best known block still has less work than our + * tip did when the timeout was set, then send a getheaders message, + * and set a shorter timeout, HEADERS_RESPONSE_TIME seconds in future. + * If their best known block is still behind when that new timeout is + * reached, disconnect. + */ + struct ChainSyncTimeoutState { + //! A timeout used for checking whether our peer has sufficiently synced + int64_t m_timeout; + //! A header with the work we require on our peer's chain + const CBlockIndex * m_work_header; + //! After timeout is reached, set to true after sending getheaders + bool m_sent_getheaders; + //! Whether this peer is protected from disconnection due to a bad/slow chain + bool m_protect; + }; + + ChainSyncTimeoutState m_chain_sync; + CNodeState(CAddress addrIn, std::string addrNameIn) : address(addrIn), name(addrNameIn) { fCurrentlyConnected = false; nMisbehavior = 0; @@ -223,6 +253,7 @@ struct CNodeState { fHaveWitness = false; fWantsCmpctWitness = false; fSupportsDesiredCmpctVersion = false; + m_chain_sync = { 0, nullptr, false, false }; } }; @@ -502,6 +533,13 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con } // namespace +// Returns true for outbound peers, excluding manual connections, feelers, and +// one-shots +bool IsOutboundDisconnectionCandidate(const CNode *node) +{ + return !(node->fInbound || node->m_manual_connection || node->fFeeler || node->fOneShot); +} + void PeerLogicValidation::InitializeNode(CNode *pnode) { CAddress addr = pnode->addr; std::string addrName = pnode->GetAddrName(); @@ -534,6 +572,8 @@ void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTim nPreferredDownload -= state->fPreferredDownload; nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0); assert(nPeersWithValidatedDownloads >= 0); + g_outbound_peers_with_protect_from_disconnect -= state->m_chain_sync.m_protect; + assert(g_outbound_peers_with_protect_from_disconnect >= 0); mapNodeState.erase(nodeid); @@ -542,6 +582,7 @@ void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTim assert(mapBlocksInFlight.empty()); assert(nPreferredDownload == 0); assert(nPeersWithValidatedDownloads == 0); + assert(g_outbound_peers_with_protect_from_disconnect == 0); } LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid); } @@ -1164,6 +1205,213 @@ inline void static SendBlockTransactions(const CBlock& block, const BlockTransac connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp)); } +bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::vector<CBlockHeader>& headers, const CChainParams& chainparams, bool punish_duplicate_invalid) +{ + const CNetMsgMaker msgMaker(pfrom->GetSendVersion()); + size_t nCount = headers.size(); + + if (nCount == 0) { + // Nothing interesting. Stop asking this peers for more headers. + return true; + } + + const CBlockIndex *pindexLast = nullptr; + { + LOCK(cs_main); + 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++; + connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256())); + LogPrint(BCLog::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->GetId(), 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; + } + + uint256 hashLastBlock; + for (const CBlockHeader& header : headers) { + if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) { + Misbehaving(pfrom->GetId(), 20); + return error("non-continuous headers sequence"); + } + hashLastBlock = header.GetHash(); + } + } + + CValidationState state; + CBlockHeader first_invalid_header; + if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast, &first_invalid_header)) { + int nDoS; + if (state.IsInvalid(nDoS)) { + LOCK(cs_main); + if (nDoS > 0) { + Misbehaving(pfrom->GetId(), nDoS); + } + if (punish_duplicate_invalid && mapBlockIndex.find(first_invalid_header.GetHash()) != mapBlockIndex.end()) { + // Goal: don't allow outbound peers to use up our outbound + // connection slots if they are on incompatible chains. + // + // We ask the caller to set punish_invalid appropriately based + // on the peer and the method of header delivery (compact + // blocks are allowed to be invalid in some circumstances, + // under BIP 152). + // Here, we try to detect the narrow situation that we have a + // valid block header (ie it was valid at the time the header + // was received, and hence stored in mapBlockIndex) but know the + // block is invalid, and that a peer has announced that same + // block as being on its active chain. + // Disconnect the peer in such a situation. + // + // Note: if the header that is invalid was not accepted to our + // mapBlockIndex at all, that may also be grounds for + // disconnecting the peer, as the chain they are on is likely + // to be incompatible. However, there is a circumstance where + // that does not hold: if the header's timestamp is more than + // 2 hours ahead of our current time. In that case, the header + // may become valid in the future, and we don't want to + // disconnect a peer merely for serving us one too-far-ahead + // block header, to prevent an attacker from splitting the + // network by mining a block right at the 2 hour boundary. + // + // TODO: update the DoS logic (or, rather, rewrite the + // DoS-interface between validation and net_processing) so that + // the interface is cleaner, and so that we disconnect on all the + // reasons that a peer's headers chain is incompatible + // with ours (eg block->nVersion softforks, MTP violations, + // etc), and not just the duplicate-invalid case. + pfrom->fDisconnect = true; + } + return error("invalid header received"); + } + } + + { + LOCK(cs_main); + CNodeState *nodestate = State(pfrom->GetId()); + if (nodestate->nUnconnectingHeaders > 0) { + LogPrint(BCLog::NET, "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->GetId(), nodestate->nUnconnectingHeaders); + } + nodestate->nUnconnectingHeaders = 0; + + assert(pindexLast); + UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash()); + + // From here, pindexBestKnownBlock should be guaranteed to be non-null, + // because it is set in UpdateBlockAvailability. Some nullptr checks + // are still present, however, as belt-and-suspenders. + + if (nCount == MAX_HEADERS_RESULTS) { + // Headers message had its maximum size; the peer may have more headers. + // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue + // from there instead. + LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->GetId(), pfrom->nStartingHeight); + connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256())); + } + + bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus()); + // 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) { + std::vector<const CBlockIndex*> vToFetch; + const CBlockIndex *pindexWalk = pindexLast; + // Calculate all the blocks we'd need to switch to pindexLast, up to a limit. + while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) { + if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) && + !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) && + (!IsWitnessEnabled(pindexWalk->pprev, chainparams.GetConsensus()) || State(pfrom->GetId())->fHaveWitness)) { + // We don't have this block, and it's not yet in flight. + vToFetch.push_back(pindexWalk); + } + pindexWalk = pindexWalk->pprev; + } + // If pindexWalk still isn't on our main chain, we're looking at a + // very large reorg at a time we think we're close to caught up to + // the main chain -- this shouldn't really happen. Bail out on the + // direct fetch and rely on parallel download instead. + if (!chainActive.Contains(pindexWalk)) { + LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n", + pindexLast->GetBlockHash().ToString(), + pindexLast->nHeight); + } else { + std::vector<CInv> vGetData; + // Download as much as possible, from earliest to latest. + for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) { + if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) { + // Can't download any more from this peer + break; + } + uint32_t nFetchFlags = GetFetchFlags(pfrom); + vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash())); + MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex); + LogPrint(BCLog::NET, "Requesting block %s from peer=%d\n", + pindex->GetBlockHash().ToString(), pfrom->GetId()); + } + if (vGetData.size() > 1) { + LogPrint(BCLog::NET, "Downloading blocks toward %s (%d) via headers direct fetch\n", + pindexLast->GetBlockHash().ToString(), pindexLast->nHeight); + } + if (vGetData.size() > 0) { + if (nodestate->fSupportsDesiredCmpctVersion && vGetData.size() == 1 && mapBlocksInFlight.size() == 1 && pindexLast->pprev->IsValid(BLOCK_VALID_CHAIN)) { + // In any case, we want to download using a compact block, not a regular one + vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash); + } + connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData)); + } + } + } + // If we're in IBD, we want outbound peers that will serve us a useful + // chain. Disconnect peers that are on chains with insufficient work. + if (IsInitialBlockDownload() && nCount != MAX_HEADERS_RESULTS) { + // When nCount < MAX_HEADERS_RESULTS, we know we have no more + // headers to fetch from this peer. + if (nodestate->pindexBestKnownBlock && nodestate->pindexBestKnownBlock->nChainWork < nMinimumChainWork) { + // This peer has too little work on their headers chain to help + // us sync -- disconnect if using an outbound slot (unless + // whitelisted or addnode). + // Note: We compare their tip to nMinimumChainWork (rather than + // chainActive.Tip()) because we won't start block download + // until we have a headers chain that has at least + // nMinimumChainWork, even if a peer has a chain past our tip, + // as an anti-DoS measure. + if (IsOutboundDisconnectionCandidate(pfrom)) { + LogPrintf("Disconnecting outbound peer %d -- headers chain has insufficient work\n", pfrom->GetId()); + pfrom->fDisconnect = true; + } + } + } + + if (!pfrom->fDisconnect && IsOutboundDisconnectionCandidate(pfrom) && nodestate->pindexBestKnownBlock != nullptr) { + // If this is an outbound peer, check to see if we should protect + // it from the bad/lagging chain logic. + if (g_outbound_peers_with_protect_from_disconnect < MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT && nodestate->pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork && !nodestate->m_chain_sync.m_protect) { + nodestate->m_chain_sync.m_protect = true; + ++g_outbound_peers_with_protect_from_disconnect; + } + } + } + + return true; +} + bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStream& vRecv, int64_t nTimeReceived, const CChainParams& chainparams, CConnman* connman, const std::atomic<bool>& interruptMsgProc) { LogPrint(BCLog::NET, "received: %s (%u bytes) peer=%d\n", SanitizeString(strCommand), vRecv.size(), pfrom->GetId()); @@ -2006,7 +2254,6 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr // If we end up treating this as a plain headers message, call that as well // without cs_main. bool fRevertToHeaderProcessing = false; - CDataStream vHeadersMsg(SER_NETWORK, PROTOCOL_VERSION); // Keep a CBlock for "optimistic" compactblock reconstructions (see // below) @@ -2123,10 +2370,6 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr return true; } else { // If this was an announce-cmpctblock, we want the same treatment as a header message - // Dirty hack to process as if it were just a headers message (TODO: move message handling into their own functions) - std::vector<CBlock> headers; - headers.push_back(cmpctblock.header); - vHeadersMsg << headers; fRevertToHeaderProcessing = true; } } @@ -2135,8 +2378,14 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr if (fProcessBLOCKTXN) return ProcessMessage(pfrom, NetMsgType::BLOCKTXN, blockTxnMsg, nTimeReceived, chainparams, connman, interruptMsgProc); - if (fRevertToHeaderProcessing) - return ProcessMessage(pfrom, NetMsgType::HEADERS, vHeadersMsg, nTimeReceived, chainparams, connman, interruptMsgProc); + if (fRevertToHeaderProcessing) { + // Headers received from HB compact block peers are permitted to be + // relayed before full validation (see BIP 152), so we don't want to disconnect + // the peer if the header turns out to be for an invalid block. + // Note that if a peer tries to build on an invalid chain, that + // will be detected and the peer will be banned. + return ProcessHeadersMessage(pfrom, connman, {cmpctblock.header}, chainparams, /*punish_duplicate_invalid=*/false); + } if (fBlockReconstructed) { // If we got here, we were able to optimistically reconstruct a @@ -2146,7 +2395,16 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr mapBlockSource.emplace(pblock->GetHash(), std::make_pair(pfrom->GetId(), false)); } bool fNewBlock = false; - ProcessNewBlock(chainparams, pblock, true, &fNewBlock); + // Setting fForceProcessing to true means that we bypass some of + // our anti-DoS protections in AcceptBlock, which filters + // unrequested blocks that might be trying to waste our resources + // (eg disk space). Because we only try to reconstruct blocks when + // we're close to caught up (via the CanDirectFetch() requirement + // above, combined with the behavior of not requesting blocks until + // we have a chain with at least nMinimumChainWork), and we ignore + // compact blocks with less work than our tip, it is safe to treat + // reconstructed compact blocks as having been requested. + ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock); if (fNewBlock) { pfrom->nLastBlockTime = GetTime(); } else { @@ -2226,7 +2484,11 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr bool fNewBlock = false; // Since we requested this block (it was in mapBlocksInFlight), force it to be processed, // even if it would not be a candidate for new tip (missing previous block, chain not long enough, etc) - ProcessNewBlock(chainparams, pblock, true, &fNewBlock); + // This bypasses some anti-DoS logic in AcceptBlock (eg to prevent + // disk-space attacks), but this should be safe due to the + // protections in the compact block handler -- see related comment + // in compact block optimistic reconstruction handling. + ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock); if (fNewBlock) { pfrom->nLastBlockTime = GetTime(); } else { @@ -2254,136 +2516,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr ReadCompactSize(vRecv); // ignore tx count; assume it is 0. } - if (nCount == 0) { - // Nothing interesting. Stop asking this peers for more headers. - return true; - } - - const CBlockIndex *pindexLast = nullptr; - { - LOCK(cs_main); - 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++; - connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256())); - LogPrint(BCLog::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->GetId(), 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; - } - - uint256 hashLastBlock; - for (const CBlockHeader& header : headers) { - if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) { - Misbehaving(pfrom->GetId(), 20); - return error("non-continuous headers sequence"); - } - hashLastBlock = header.GetHash(); - } - } - - CValidationState state; - if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast)) { - int nDoS; - if (state.IsInvalid(nDoS)) { - if (nDoS > 0) { - LOCK(cs_main); - Misbehaving(pfrom->GetId(), nDoS); - } - return error("invalid header received"); - } - } - - { - LOCK(cs_main); - CNodeState *nodestate = State(pfrom->GetId()); - if (nodestate->nUnconnectingHeaders > 0) { - LogPrint(BCLog::NET, "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->GetId(), nodestate->nUnconnectingHeaders); - } - nodestate->nUnconnectingHeaders = 0; - - assert(pindexLast); - UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash()); - - if (nCount == MAX_HEADERS_RESULTS) { - // Headers message had its maximum size; the peer may have more headers. - // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue - // from there instead. - LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->GetId(), pfrom->nStartingHeight); - connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256())); - } - - bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus()); - // 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) { - std::vector<const CBlockIndex*> vToFetch; - const CBlockIndex *pindexWalk = pindexLast; - // Calculate all the blocks we'd need to switch to pindexLast, up to a limit. - while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) { - if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) && - !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) && - (!IsWitnessEnabled(pindexWalk->pprev, chainparams.GetConsensus()) || State(pfrom->GetId())->fHaveWitness)) { - // We don't have this block, and it's not yet in flight. - vToFetch.push_back(pindexWalk); - } - pindexWalk = pindexWalk->pprev; - } - // If pindexWalk still isn't on our main chain, we're looking at a - // very large reorg at a time we think we're close to caught up to - // the main chain -- this shouldn't really happen. Bail out on the - // direct fetch and rely on parallel download instead. - if (!chainActive.Contains(pindexWalk)) { - LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n", - pindexLast->GetBlockHash().ToString(), - pindexLast->nHeight); - } else { - std::vector<CInv> vGetData; - // Download as much as possible, from earliest to latest. - for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) { - if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) { - // Can't download any more from this peer - break; - } - uint32_t nFetchFlags = GetFetchFlags(pfrom); - vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash())); - MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex); - LogPrint(BCLog::NET, "Requesting block %s from peer=%d\n", - pindex->GetBlockHash().ToString(), pfrom->GetId()); - } - if (vGetData.size() > 1) { - LogPrint(BCLog::NET, "Downloading blocks toward %s (%d) via headers direct fetch\n", - pindexLast->GetBlockHash().ToString(), pindexLast->nHeight); - } - if (vGetData.size() > 0) { - if (nodestate->fSupportsDesiredCmpctVersion && vGetData.size() == 1 && mapBlocksInFlight.size() == 1 && pindexLast->pprev->IsValid(BLOCK_VALID_CHAIN)) { - // In any case, we want to download using a compact block, not a regular one - vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash); - } - connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData)); - } - } - } - } + // Headers received via a HEADERS message should be valid, and reflect + // the chain the peer is on. If we receive a known-invalid header, + // disconnect the peer if it is using one of our outbound connection + // slots. + bool should_punish = !pfrom->fInbound && !pfrom->m_manual_connection; + return ProcessHeadersMessage(pfrom, connman, headers, chainparams, should_punish); } else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing @@ -2781,6 +2919,58 @@ bool PeerLogicValidation::ProcessMessages(CNode* pfrom, std::atomic<bool>& inter return fMoreWork; } +void PeerLogicValidation::ConsiderEviction(CNode *pto, int64_t time_in_seconds) +{ + AssertLockHeld(cs_main); + + CNodeState &state = *State(pto->GetId()); + const CNetMsgMaker msgMaker(pto->GetSendVersion()); + + if (!state.m_chain_sync.m_protect && IsOutboundDisconnectionCandidate(pto) && state.fSyncStarted) { + // This is an outbound peer subject to disconnection if they don't + // announce a block with as much work as the current tip within + // CHAIN_SYNC_TIMEOUT + HEADERS_RESPONSE_TIME seconds (note: if + // their chain has more work than ours, we should sync to it, + // unless it's invalid, in which case we should find that out and + // disconnect from them elsewhere). + if (state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork) { + if (state.m_chain_sync.m_timeout != 0) { + state.m_chain_sync.m_timeout = 0; + state.m_chain_sync.m_work_header = nullptr; + state.m_chain_sync.m_sent_getheaders = false; + } + } else if (state.m_chain_sync.m_timeout == 0 || (state.m_chain_sync.m_work_header != nullptr && state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= state.m_chain_sync.m_work_header->nChainWork)) { + // Our best block known by this peer is behind our tip, and we're either noticing + // that for the first time, OR this peer was able to catch up to some earlier point + // where we checked against our tip. + // Either way, set a new timeout based on current tip. + state.m_chain_sync.m_timeout = time_in_seconds + CHAIN_SYNC_TIMEOUT; + state.m_chain_sync.m_work_header = chainActive.Tip(); + state.m_chain_sync.m_sent_getheaders = false; + } else if (state.m_chain_sync.m_timeout > 0 && time_in_seconds > state.m_chain_sync.m_timeout) { + // No evidence yet that our peer has synced to a chain with work equal to that + // of our tip, when we first detected it was behind. Send a single getheaders + // message to give the peer a chance to update us. + if (state.m_chain_sync.m_sent_getheaders) { + // They've run out of time to catch up! + LogPrintf("Disconnecting outbound peer %d for old chain, best known block = %s\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>"); + pto->fDisconnect = true; + } else { + LogPrint(BCLog::NET, "sending getheaders to outbound peer=%d to verify chain work (current best known block:%s, benchmark blockhash: %s)\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>", state.m_chain_sync.m_work_header->GetBlockHash().ToString()); + connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(state.m_chain_sync.m_work_header->pprev), uint256())); + state.m_chain_sync.m_sent_getheaders = true; + constexpr int64_t HEADERS_RESPONSE_TIME = 120; // 2 minutes + // Bump the timeout to allow a response, which could clear the timeout + // (if the response shows the peer has synced), reset the timeout (if + // the peer syncs to the required work but not to our tip), or result + // in disconnect (if we advance to the timeout and pindexBestKnownBlock + // has not sufficiently progressed) + state.m_chain_sync.m_timeout = time_in_seconds + HEADERS_RESPONSE_TIME; + } + } + } +} + class CompareInvMempoolOrder { CTxMemPool *mp; @@ -3247,6 +3437,9 @@ bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptM } } + // Check that outbound peers have reasonable chains + // GetTime() is used by this anti-DoS logic so we can test this using mocktime + ConsiderEviction(pto, GetTime()); // // Message: getdata (blocks) |