From: CryptoManiac <balthazar@yandex.ru>
Date: Mon, 28 Jul 2014 18:57:22 +0000 (+0400)
Subject: Make sure we always have a node to do IBD from
X-Git-Tag: v0.4.4.6-nvc-update7~5^2~1
X-Git-Url: https://git.novaco.in/?p=novacoin.git;a=commitdiff_plain;h=28f9882707d389250e307ebf58dcf981340f1381

Make sure we always have a node to do IBD from

This introduces the concept of the 'sync node', which is the one we
asked for missing blocks. In case the sync node goes away, a new one
will be selected.
---

diff --git a/src/main.cpp b/src/main.cpp
index fa8f993..9a521fe 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3985,6 +3985,12 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
                 pto->PushMessage("ping");
         }
 
+        // Start block sync
+        if (pto->fStartSync) {
+            pto->fStartSync = false;
+            pto->PushGetBlocks(pindexBest, uint256(0));
+        }
+
         // Resend wallet transactions that haven't gotten in a block yet
         ResendWalletTransactions();
 
diff --git a/src/net.cpp b/src/net.cpp
index 16439a7..cd826d6 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -55,6 +55,7 @@ static map<CNetAddr, LocalServiceInfo> mapLocalHost;
 static bool vfReachable[NET_MAX] = {};
 static bool vfLimited[NET_MAX] = {};
 static CNode* pnodeLocalHost = NULL;
+static CNode* pnodeSync = NULL;
 CAddress addrSeenByPeer(CService("0.0.0.0", 0), nLocalServices);
 uint64 nLocalHostNonce = 0;
 array<int, THREAD_MAX> vnThreadsRunning;
@@ -539,6 +540,15 @@ void CNode::CloseSocketDisconnect()
         hSocket = INVALID_SOCKET;
         vRecv.clear();
     }
+
+    // in case this fails, we'll empty the recv buffer when the CNode is deleted
+    TRY_LOCK(cs_vRecv, lockRecv);
+    if (lockRecv)
+        vRecv.clear();
+
+    // if this was the sync node, we'll need a new one
+    if (this == pnodeSync)
+        pnodeSync = NULL;
 }
 
 void CNode::Cleanup()
@@ -1572,12 +1582,37 @@ bool OpenNetworkConnection(const CAddress& addrConnect, CSemaphoreGrant *grantOu
     return true;
 }
 
+// for now, use a very simple selection metric: the node from which we received
+// most recently
+double static NodeSyncScore(const CNode *pnode) {
+    return -pnode->nLastRecv;
+}
 
-
-
-
-
-
+void static StartSync(const vector<CNode*> &vNodes) {
+    CNode *pnodeNewSync = NULL;
+    double dBestScore = 0;
+
+    // Iterate over all nodes
+    BOOST_FOREACH(CNode* pnode, vNodes) {
+        // check preconditions for allowing a sync
+        if (!pnode->fClient && !pnode->fOneShot &&
+            !pnode->fDisconnect && pnode->fSuccessfullyConnected &&
+            (pnode->nStartingHeight > (nBestHeight - 144)) &&
+            (pnode->nVersion < NOBLKS_VERSION_START || pnode->nVersion >= NOBLKS_VERSION_END)) {
+            // if ok, compare node's score with the best so far
+            double dScore = NodeSyncScore(pnode);
+            if (pnodeNewSync == NULL || dScore > dBestScore) {
+                pnodeNewSync = pnode;
+                dBestScore = dScore;
+            }
+        }
+    }
+    // if a new sync candidate was found, start sync!
+    if (pnodeNewSync) {
+        pnodeNewSync->fStartSync = true;
+        pnodeSync = pnodeNewSync;
+    }
+}
 
 void ThreadMessageHandler(void* parg)
 {
@@ -1606,14 +1641,21 @@ void ThreadMessageHandler2(void* parg)
     SetThreadPriority(THREAD_PRIORITY_BELOW_NORMAL);
     while (!fShutdown)
     {
+        bool fHaveSyncNode = false;
         vector<CNode*> vNodesCopy;
         {
             LOCK(cs_vNodes);
             vNodesCopy = vNodes;
-            BOOST_FOREACH(CNode* pnode, vNodesCopy)
+            BOOST_FOREACH(CNode* pnode, vNodesCopy) {
                 pnode->AddRef();
+                if (pnode == pnodeSync)
+                    fHaveSyncNode = true;
+            }
         }
 
+        if (!fHaveSyncNode)
+            StartSync(vNodesCopy);
+
         // Poll the connected nodes for messages
         CNode* pnodeTrickle = NULL;
         if (!vNodesCopy.empty())
diff --git a/src/net.h b/src/net.h
index 0d51bff..c1d478a 100644
--- a/src/net.h
+++ b/src/net.h
@@ -197,6 +197,7 @@ public:
     CBlockIndex* pindexLastGetBlocksBegin;
     uint256 hashLastGetBlocksEnd;
     int nStartingHeight;
+    bool fStartSync;
 
     // flood relay
     std::vector<CAddress> vAddrToSend;
@@ -237,6 +238,7 @@ public:
         pindexLastGetBlocksBegin = 0;
         hashLastGetBlocksEnd = 0;
         nStartingHeight = -1;
+        fStartSync = false;
         fGetAddr = false;
         nMisbehavior = 0;
         hashCheckpointKnown = 0;