new CNetworkBlockHeader for robust compat

src/main.cpp

@@ -6015,8 +6015,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 pindex = chainActive.Next(pindex);
         }
 
-        // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
-        vector<CBlockHeader> vHeaders;
+        // we must use CNetworkBlockHeader, as CBlockHeader won't include the 0x00 nTx count at the end for compatibility
+        vector<CNetworkBlockHeader> vHeaders;
         int nLimit = MAX_HEADERS_RESULTS;
         LogPrint("net", "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString(), pfrom->id);
         //if ( pfrom->lasthdrsreq >= chainActive.Height()-MAX_HEADERS_RESULTS || pfrom->lasthdrsreq != (int32_t)(pindex ? pindex->nHeight : -1) )// no need to ever suppress this
@@ -6170,8 +6170,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 Misbehaving(pfrom->GetId(), nDoS);
         }
     }
-    
-    
+
     else if (strCommand == "headers" && !fImporting && !fReindex) // Ignore headers received while importing
     {
         std::vector<CBlockHeader> headers;
@@ -6185,7 +6184,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         headers.resize(nCount);
         for (unsigned int n = 0; n < nCount; n++) {
             vRecv >> headers[n];
-            //ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
+            ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
         }
         
         LOCK(cs_main);

src/primitives/block.h

@@ -129,6 +129,42 @@ public:
     }
 };
 
+// this class is used to address the type mismatch that existed between nodes, where block headers
+// were being serialized by senders as CBlock and deserialized as CBlockHeader + an assumed extra
+// compact value. although it was working, I made this because it did break, and makes the connection
+// between CBlock and CBlockHeader more brittle.
+// by using this intentionally specified class instead, we remove an instability in the code that could break
+// due to unrelated changes, but stay compatible with the old method.
+class CNetworkBlockHeader : public CBlockHeader
+{
+    public:
+        std::vector<CTransaction> compatVec;
+
+    CNetworkBlockHeader() : CBlockHeader()
+    {
+        SetNull();
+    }
+
+    CNetworkBlockHeader(const CBlockHeader &header)
+    {
+        SetNull();
+        *((CBlockHeader*)this) = header;
+    }
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
+        READWRITE(*(CBlockHeader*)this);
+        READWRITE(compatVec);
+    }
+
+    void SetNull()
+    {
+        CBlockHeader::SetNull();
+        compatVec.clear();    
+    }
+};
 
 class CBlock : public CBlockHeader
 {
@@ -147,6 +183,7 @@ public:
     CBlock(const CBlockHeader &header)
     {
         SetNull();
+        *((CBlockHeader*)this) = header;
     }
 
     ADD_SERIALIZE_METHODS;