From 8977e99906e81aa59db1bb986a366ef53a62bc3e Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Wed, 1 Mar 2017 15:12:35 -0800
Subject: [PATCH] mempool: extra sanity checking for mining.

---
 lib/mempool/mempool.js | 9 +++++++++
 lib/mining/miner.js    | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index e9e48f2e..f952059b 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -88,6 +88,7 @@ function Mempool(options) {
   this.freeCount = 0;
   this.lastTime = 0;
   this.lastFlush = 0;
+  this.tip = this.network.genesis.hash;
 
   this.waiting = {};
   this.orphans = {};
@@ -150,6 +151,8 @@ Mempool.prototype._open = co(function* open() {
     }
   }
 
+  this.tip = this.chain.tip.hash;
+
   this.logger.info('Mempool loaded (maxsize=%dkb).', size);
 });
 
@@ -227,6 +230,8 @@ Mempool.prototype._addBlock = co(function* addBlock(block, txs) {
 
   yield this.cache.flush();
 
+  this.tip = block.hash;
+
   if (entries.length === 0)
     return;
 
@@ -291,6 +296,8 @@ Mempool.prototype._removeBlock = co(function* removeBlock(block, txs) {
 
   yield this.cache.flush();
 
+  this.tip = block.prevBlock;
+
   if (total === 0)
     return;
 
@@ -345,6 +352,8 @@ Mempool.prototype._reset = co(function* reset() {
     yield this.cache.wipe();
     this.cache.clear();
   }
+
+  this.tip = this.chain.tip.hash;
 });
 
 /**
diff --git a/lib/mining/miner.js b/lib/mining/miner.js
index bb5db248..cfd633da 100644
--- a/lib/mining/miner.js
+++ b/lib/mining/miner.js
@@ -389,6 +389,9 @@ Miner.prototype.build = function build(attempt) {
   if (!this.mempool)
     return [];
 
+  assert(this.mempool.tip === this.chain.tip.hash,
+    'Mempool/chain tip mismatch! Unsafe to create block.');
+
   hashes = this.mempool.getSnapshot();
 
   for (i = 0; i < hashes.length; i++) {