protocol: add checks for top block hard fork version

We won't even talk to a peer which claims a wrong version
for its top block. This will avoid syncing to known bad
peers in the first place.
Also add IP fails when failing to verify a block.

src/cryptonote_core/blockchain.h

@@ -745,6 +745,15 @@ namespace cryptonote
      */
     uint8_t get_ideal_hard_fork_version(uint64_t height) const { return m_hardfork->get_ideal_version(height); }
 
+    /**
+     * @brief returns the actual hardfork version for a given block height
+     *
+     * @param height the height for which to check version info
+     *
+     * @return the version
+     */
+    uint8_t get_hard_fork_version(uint64_t height) const { return m_hardfork->get(height); }
+
     /**
      * @brief get information about hardfork voting for a version
      *

src/cryptonote_protocol/cryptonote_protocol_defs.h

@@ -195,10 +195,12 @@ namespace cryptonote
   {
     uint64_t current_height;
     crypto::hash  top_id;
+    uint8_t top_version;
 
     BEGIN_KV_SERIALIZE_MAP()
       KV_SERIALIZE(current_height)
       KV_SERIALIZE_VAL_POD_AS_BLOB(top_id)
+      KV_SERIALIZE_OPT(top_version, (uint8_t)0)
     END_KV_SERIALIZE_MAP()
   };
 

src/cryptonote_protocol/cryptonote_protocol_handler.inl

@@ -256,6 +256,14 @@ namespace cryptonote
     if(context.m_state == cryptonote_connection_context::state_synchronizing)
       return true;
 
+    // from v6, if the peer advertises a top block version, reject if it's not what it should be (will only work if no voting)
+    const uint8_t version = m_core.get_blockchain_storage().get_ideal_hard_fork_version(hshd.current_height - 1);
+    if (version >= 6 && version != hshd.top_version)
+    {
+      LOG_DEBUG_CC(context, "Ignoring due to wrong top version (" << hshd.top_version << ", expected " << version);
+      return false;
+    }
+
     uint64_t target = m_core.get_target_blockchain_height();
     if (target == 0)
       target = m_core.get_current_blockchain_height();
@@ -297,6 +305,7 @@ namespace cryptonote
   bool t_cryptonote_protocol_handler<t_core>::get_payload_sync_data(CORE_SYNC_DATA& hshd)
   {
     m_core.get_blockchain_top(hshd.current_height, hshd.top_id);
+    hshd.top_version = m_core.get_blockchain_storage().get_hard_fork_version(hshd.current_height);
     hshd.current_height +=1;
     return true;
   }
@@ -348,6 +357,7 @@ namespace cryptonote
     {
       LOG_PRINT_CCONTEXT_L0("Block verification failed, dropping connection");
       m_p2p->drop_connection(context);
+      m_p2p->add_host_fail(context.m_remote_address);
       m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
@@ -616,6 +626,7 @@ namespace cryptonote
         {
           LOG_PRINT_CCONTEXT_L0("Block verification failed, dropping connection");
           m_p2p->drop_connection(context);
+          m_p2p->add_host_fail(context.m_remote_address);
           m_block_queue.flush_spans(context.m_connection_id);
           return 1;
         }