Fix issue #848 : broken mining on testnet

src/bitcoinrpc.cpp

@@ -1816,7 +1816,7 @@ Value getwork(const Array& params, bool fHelp)
         }
 
         // Update nTime
-        pblock->nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+        pblock->UpdateTime(pindexPrev);
         pblock->nNonce = 0;
 
         // Update nExtraNonce
@@ -1916,7 +1916,7 @@ Value getmemorypool(const Array& params, bool fHelp)
         }
 
         // Update nTime
-        pblock->nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+        pblock->UpdateTime(pindexPrev);
         pblock->nNonce = 0;
 
         Array transactions;

src/main.cpp

@@ -922,6 +922,15 @@ void static InvalidChainFound(CBlockIndex* pindexNew)
         printf("InvalidChainFound: WARNING: Displayed transactions may not be correct!  You may need to upgrade, or other nodes may need to upgrade.\n");
 }
 
+void CBlock::UpdateTime(const CBlockIndex* pindexPrev)
+{
+    nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+
+    // Updating time can change work required on testnet:
+    if (fTestNet)
+        nBits = GetNextWorkRequired(pindexPrev, this);
+}
+
 
 
 
@@ -3168,7 +3177,7 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
     // Fill in header
     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
     pblock->hashMerkleRoot = pblock->BuildMerkleTree();
-    pblock->nTime          = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+    pblock->UpdateTime(pindexPrev);
     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock.get());
     pblock->nNonce         = 0;
 
@@ -3326,6 +3335,7 @@ void static BitcoinMiner(CWallet *pwallet)
         FormatHashBuffers(pblock.get(), pmidstate, pdata, phash1);
 
         unsigned int& nBlockTime = *(unsigned int*)(pdata + 64 + 4);
+        unsigned int& nBlockBits = *(unsigned int*)(pdata + 64 + 8);
         unsigned int& nBlockNonce = *(unsigned int*)(pdata + 64 + 12);
 
 
@@ -3413,8 +3423,14 @@ void static BitcoinMiner(CWallet *pwallet)
                 break;
 
             // Update nTime every few seconds
-            pblock->nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+            pblock->UpdateTime(pindexPrev);
             nBlockTime = ByteReverse(pblock->nTime);
+            if (fTestNet)
+            {
+                // Changing pblock->nTime can change work required on testnet:
+                nBlockBits = ByteReverse(pblock->nBits);
+                hashTarget = CBigNum().SetCompact(pblock->nBits).getuint256();
+            }
         }
     }
 }

src/main.h

@@ -913,6 +913,7 @@ public:
         return (int64)nTime;
     }
 
+    void UpdateTime(const CBlockIndex* pindexPrev);
 
 
     uint256 BuildMerkleTree() const