From 4e4265a4d7439ae615b21aaa5176565afb3a40fc Mon Sep 17 00:00:00 2001
From: Daniel Kraft <d@domob.eu>
Date: Sat, 22 Nov 2014 16:06:34 +0100
Subject: [PATCH] Enforce that auxpow parent blocks have no auxpow block
 version.

This is for compatibility with namecoind.  See also
https://github.com/namecoin/namecoin/pull/199.
---
 TODO         |  4 +++-
 src/auxpow.h | 12 ++++++++++++
 src/main.cpp |  7 +++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/TODO b/TODO
index 5b37c6bd0b..766e88c6d5 100644
--- a/TODO
+++ b/TODO
@@ -1,9 +1,9 @@
 * soft fork in namecoind:
   + prevent "name_new stealing" in memory pool
   + enforce nametx-version also for name *outputs*
+  + disallow auxpow parent blocks with auxpow
   - limit DB locks / unique tx
   - disallow greedy names
-  - disallow auxpow parent blocks with auxpow
   - update fee logic?
 
 * handle seed nodes / DNS seeds
@@ -15,6 +15,8 @@
   - P2SH as enforced soft fork (BIP16)
   - strict BIP30 as enforced soft fork
   - allow larger blocks (DB locks)
+  - no need to disallow auxpow parent blocks with auxpow-flag in the version
+    any more; instead, the auxpow is simply never loaded for them
   - name_new format change?
   - more differences???
 
diff --git a/src/auxpow.h b/src/auxpow.h
index 2ab32eb9a2..1dc60dfb02 100644
--- a/src/auxpow.h
+++ b/src/auxpow.h
@@ -151,6 +151,18 @@ class CAuxPow : public CMerkleTx
     return parentBlock.GetHash ();
   }
 
+  /**
+   * Return parent block.  This is only used for the temporary parentblock
+   * auxpow version check.
+   * @return The parent block.
+   */
+  /* FIXME: Remove after the hardfork.  */
+  inline const CPureBlockHeader&
+  getParentBlock () const
+  {
+    return parentBlock;
+  }
+
   /**
    * Calculate the expected index in the merkle tree.  This is also used
    * for the test-suite.
diff --git a/src/main.cpp b/src/main.cpp
index 06d0f993c6..b033872f93 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1194,9 +1194,16 @@ bool CheckProofOfWork(const CBlockHeader& block)
     }
 
     /* We have auxpow.  Check it.  */
+
     if (!block.nVersion.IsAuxpow())
         return error("%s : auxpow on block with non-auxpow version", __func__);
 
+    /* Temporary check:  Disallow parent blocks with auxpow version.  This is
+       for compatibility with the old client.  */
+    /* FIXME: Remove this check with a hardfork later on.  */
+    if (block.auxpow->getParentBlock().nVersion.IsAuxpow())
+        return error("%s : auxpow parent block has auxpow version", __func__);
+
     if (!block.auxpow->check(block.GetHash(), block.nVersion.GetChainId()))
         return error("%s : AUX POW is not valid", __func__);
     if (!CheckProofOfWork(block.auxpow->getParentBlockHash(), block.nBits))