From eb3f661add15837434c286476a32e05f279a1919 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Sun, 18 Mar 2012 23:47:26 +0100 Subject: [PATCH 1/2] Prevent stuck block download in large reorganisations In cases of very large reorganisations (hundreds of blocks), a situation may appear where an 'inv' is sent as response to a 'getblocks', but the last block mentioned in the inv is already known to the receiver node. However, the supplying node uses a request for this last block as a trigger to send the rest of the inv blocks. If it never comes, the block chain download is stuck. This commit makes the receiver node always request the last inv'ed block, even if it is already known, to prevent this problem. --- src/main.cpp | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index 67d6638e0e5..167e2821c0a 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -2178,8 +2178,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv) return error("message inv size() = %d", vInv.size()); CTxDB txdb("r"); - BOOST_FOREACH(const CInv& inv, vInv) + for (int nInv = 0; nInv < vInv.size(); nInv++) { + const CInv &inv = vInv[nInv]; + if (fShutdown) return true; pfrom->AddInventoryKnown(inv); @@ -2188,9 +2190,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv) if (fDebug) printf(" got inventory: %s %s\n", inv.ToString().c_str(), fAlreadyHave ? "have" : "new"); - if (!fAlreadyHave) + // Always request the last block in an inv bundle (even if we already have it), as it is the + // trigger for the other side to send further invs. If we are stuck on a (very long) side chain, + // this is necessary to connect earlier received orphan blocks to the chain again. + if (!fAlreadyHave || (inv.type == MSG_BLOCK && nInv==vInv.size()-1)) pfrom->AskFor(inv); - else if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) + if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) pfrom->PushGetBlocks(pindexBest, GetOrphanRoot(mapOrphanBlocks[inv.hash])); // Track requests for our stuff From 2403bb79bc232ea3f9a78448d0fb4ffcf385d209 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Sat, 5 May 2012 04:04:38 +0200 Subject: [PATCH 2/2] Prevent stuck download: correct solution Pull request #948 introduced a fix for nodes stuck on a long side branch of the main chain. The fix was non-functional however, as the additional getdata request was created in a first step of processing, but dropped in a second step as it was considered redundant. This commits fixes it by sending the request directly. --- src/main.cpp | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index 167e2821c0a..a2fc7387fba 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -2177,6 +2177,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv) if (vInv.size() > 50000) return error("message inv size() = %d", vInv.size()); + // find last block in inv vector + unsigned int nLastBlock = (unsigned int)(-1); + for (unsigned int nInv = 0; nInv < vInv.size(); nInv++) { + if (vInv[vInv.size() - 1 - nInv].type == MSG_BLOCK) + nLastBlock = vInv.size() - 1 - nInv; + } CTxDB txdb("r"); for (int nInv = 0; nInv < vInv.size(); nInv++) { @@ -2193,9 +2199,15 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv) // Always request the last block in an inv bundle (even if we already have it), as it is the // trigger for the other side to send further invs. If we are stuck on a (very long) side chain, // this is necessary to connect earlier received orphan blocks to the chain again. - if (!fAlreadyHave || (inv.type == MSG_BLOCK && nInv==vInv.size()-1)) + if (fAlreadyHave && nInv == nLastBlock) { + // bypass mapAskFor, and send request directly; it must go through. + std::vector vGetData(1,inv); + pfrom->PushMessage("getdata", vGetData); + } + + if (!fAlreadyHave) pfrom->AskFor(inv); - if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) + else if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) pfrom->PushGetBlocks(pindexBest, GetOrphanRoot(mapOrphanBlocks[inv.hash])); // Track requests for our stuff