From e912f78814c3ccc1fda2aeda2f7773bc0991f7c4 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Tue, 16 Feb 2016 03:03:11 -0800
Subject: [PATCH] async chain.

---
 lib/bcoin/block.js   |  16 +-
 lib/bcoin/chain.js   | 377 +++++++++++++++++++++++++++++--------------
 lib/bcoin/chaindb.js |   4 +-
 lib/bcoin/node.js    |  12 ++
 lib/bcoin/pool.js    | 301 +++++++++++++++++++---------------
 lib/bcoin/utils.js   |   4 +-
 6 files changed, 457 insertions(+), 257 deletions(-)

diff --git a/lib/bcoin/block.js b/lib/bcoin/block.js
index bb7feb8f..b17b9d65 100644
--- a/lib/bcoin/block.js
+++ b/lib/bcoin/block.js
@@ -443,6 +443,8 @@ Block.prototype.verifyContext = function verifyContext() {
     }
 
     // BIP30 - Ensure there are no duplicate txids
+    // this.node.hasTX(tx.hash('hex'), function(err, has) {
+    //   if (has)
     if (this.chain[tx.hash('hex')]) {
       // Blocks 91842 and 91880 created duplicate
       // txids by using the same exact output script
@@ -465,19 +467,19 @@ Block.prototype.verifyContext = function verifyContext() {
         if (!input.output)
           continue;
 
-        assert(input.output);
+        // Ensure tx is not double spending an output
+        if (!input.output) {
+          utils.debug('Block is using spent inputs: %s (tx: %s, output: %s)',
+            this.rhash, tx.hash('hex'),
+            input.prevout.hash + '/' + input.prevout.index);
+          return false;
+        }
 
         // Verify the script
         if (!tx.verify(j, true, flags)) {
           utils.debug('Block has invalid inputs: %s', this.rhash);
           return false;
         }
-
-        // Ensure tx is not double spending an output
-        // if (this.chain.isSpent(input.prevout.hash, input.prevout.index)) {
-        //   utils.debug('Block is using spent inputs: %s', this.rhash);
-        //   return false;
-        // }
       }
     }
   }
diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index a47101cc..ea6ccfd2 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -259,50 +259,149 @@ Chain.prototype._preload = function _preload(callback) {
   });
 };
 
-Chain.prototype._addEntry = function _addEntry(entry) {
+Chain.prototype._saveBlock = function _saveBlock(block, callback) {
+  var node = bcoin.node.global;
+
+  if (!node)
+    return callback();
+
+  node.block.saveBlock(block, function(err) {
+    if (err)
+      return callback(err);
+
+    node.mempool.addBlock(block);
+
+    return callback();
+  });
+};
+
+Chain.prototype._fillCoins = function _fillCoin(block, callback) {
+  var node = bcoin.node.global;
+
+  if (!node)
+    return callback();
+
+  node.block.fillCoins(block, callback);
+};
+
+Chain.prototype._verifyContext = function _verifyContext(block, prev, callback) {
+  var node = bcoin.node.global;
+
+  if (!node)
+    return callback(null, block.verifyContext());
+
+  var height = prev.height + 1;
+  var scriptChecks = true;
+
+  node.block.fillCoins(block, function(err) {
+    var pending;
+
+    if (err)
+      return callback(err);
+
+    pending = block.txs.length;
+
+    // If we are an ancestor of a checkpoint, we can
+    // skip the input verification.
+    if (height < network.checkpoints.lastHeight && !network.checkpoints[height])
+      scriptChecks = false;
+
+    if (!block.verifyContext())
+      return callback(null, false);
+
+    if (!pending)
+      return callback(null, true);
+
+    // Check all transactions
+    block.txs.forEach(function(tx) {
+      var i;
+      for (i = 0; j < tx.inputs.length; i++) {
+        input = tx.inputs[i];
+        // Ensure tx is not double spending an output
+        if (!input.output) {
+          utils.debug('Block is using spent inputs: %s (tx: %s, output: %s)',
+            this.rhash, tx.hash('hex'),
+            input.prevout.hash + '/' + input.prevout.index);
+          return callback(null, false);
+        }
+      }
+      // BIP30 - Ensure there are no duplicate txids
+      node.block.hasTX(tx.hash('hex'), function(err, has) {
+        // Blocks 91842 and 91880 created duplicate
+        // txids by using the same exact output script
+        // and extraNonce.
+        if (has) {
+          utils.debug('Block is overwriting txids: %s', this.rhash);
+          if (!(network.type === 'main' && (height === 91842 || height === 91880)))
+            return callback(null, false);
+        }
+        return callback(null, true);
+      });
+    });
+  });
+};
+
+
+Chain.prototype._removeBlock = function _removeBlock(tip, callback) {
+  var node = bcoin.node.global;
+
+  if (!node)
+    return callback();
+
+  node.block.removeBlock(tip, function(err, block) {
+    if (err)
+      return callback(err);
+
+    if (!block)
+      return;
+
+    node.mempool.removeBlock(block);
+  });
+};
+
+Chain.prototype._addEntry = function _addEntry(entry, block, callback) {
   var self = this;
   var existing;
 
+  callback = utils.asyncify(callback);
+
   // Already added
   if (this.heightLookup[entry.hash] != null) {
     assert(this.heightLookup[entry.hash] === entry.height);
-    return Chain.codes.unchanged;
+    return callback(null, Chain.codes.unchanged);
   }
 
   // Duplicate height
   existing = this.db.get(entry.height);
   if (existing && existing.hash === entry.hash)
-    return Chain.codes.unchanged;
+    return callback(null, Chain.codes.unchanged);
 
-  // Fork at checkpoint
-  checkpoint = network.checkpoints[entry.height];
-  if (checkpoint) {
-    this.emit('checkpoint', entry.height, entry.hash, checkpoint);
-    if (hash !== checkpoint) {
-      // Resetting to the last checkpoint _really_ isn't
-      // necessary (even bitcoind doesn't do it), but it
-      // could be used if you want to be on the overly
-      // safe (see: paranoid) side.
-      // this.resetLastCheckpoint(entry.height);
-      return Chain.codes.badCheckpoint;
-    }
-  }
+  this._saveBlock(block, function(err) {
+    if (err)
+      return callback(err);
 
-  this._saveEntry(entry, true);
+    self._saveEntry(entry, function(err) {
+      if (err)
+        return callback(err);
 
-  return Chain.codes.okay;
+      return callback(null, Chain.codes.okay);
+    });
+  });
 };
 
-Chain.prototype._saveEntry = function _saveEntry(entry, save) {
-  if (save)
-    this.db.save(entry);
-
+Chain.prototype._saveEntry = function _saveEntry(entry, callback) {
   this.heightLookup[entry.hash] = entry.height;
 
   if (!this.tip || entry.height > this.tip.height) {
     this.tip = entry;
     this.emit('tip', this.tip);
   }
+
+  if (callback) {
+    if (typeof callback !== 'function')
+      callback = null;
+    this.db.save(entry, callback);
+  }
 };
 
 Chain.prototype.resetLastCheckpoint = function resetLastCheckpoint(height) {
@@ -355,18 +454,19 @@ Chain.prototype.resetTime = function resetTime(ts) {
   return this.resetHeight(entry.height);
 };
 
-Chain.prototype.add = function add(block, peer) {
+Chain.prototype.add = function add(block, peer, callback) {
+  var self = this;
   var initial = block;
   var code = Chain.codes.unchanged;
-  var hash, prevHash, prevHeight, entry, tip, existing;
+  var hash, prevHash, prevHeight, entry, tip, existing, checkpoint;
   var total = 0;
 
-  for (;;) {
+  (function next() {
     hash = block.hash('hex');
     prevHash = block.prevBlock;
 
     // Find the previous block height/index.
-    prevHeight = this.heightLookup[prevHash];
+    prevHeight = self.heightLookup[prevHash];
 
     // Validate the block we want to add.
     // This is only necessary for new
@@ -374,50 +474,50 @@ Chain.prototype.add = function add(block, peer) {
     // orphans.
     if (block === initial && !block.verify()) {
       code = Chain.codes.invalid;
-      this.emit('invalid', {
+      self.emit('invalid', {
         height: prevHeight + 1,
         hash: hash
       }, peer);
-      break;
+      return done(null, code);
     }
 
     // If the block is already known to be
     // an orphan, ignore it.
-    if (this.orphan.map[prevHash]) {
+    if (self.orphan.map[prevHash]) {
       // If the orphan chain forked, simply
       // reset the orphans and find a new peer.
-      if (this.orphan.map[prevHash].hash('hex') !== hash) {
-        this.orphan.map = {};
-        this.orphan.bmap = {};
-        this.orphan.count = 0;
-        this.orphan.size = 0;
-        this.emit('fork', {
+      if (self.orphan.map[prevHash].hash('hex') !== hash) {
+        self.orphan.map = {};
+        self.orphan.bmap = {};
+        self.orphan.count = 0;
+        self.orphan.size = 0;
+        self.emit('fork', {
           height: -1,
-          expected: this.orphan.map[prevHash].hash('hex'),
+          expected: self.orphan.map[prevHash].hash('hex'),
           received: hash,
           checkpoint: false
         }, peer);
         code = Chain.codes.forked;
-        break;
+        return done(null, code);
       }
       code = Chain.codes.knownOrphan;
-      break;
+      return done(null, code);
     }
 
     // If previous block wasn't ever seen,
     // add it current to orphans and break.
     if (prevHeight == null) {
-      this.orphan.count++;
-      this.orphan.size += block.getSize();
-      this.orphan.map[prevHash] = block;
-      this.orphan.bmap[hash] = block;
+      self.orphan.count++;
+      self.orphan.size += block.getSize();
+      self.orphan.map[prevHash] = block;
+      self.orphan.bmap[hash] = block;
       code = Chain.codes.newOrphan;
       total++;
-      break;
+      return done(null, code);
     }
 
     // Create a new chain entry.
-    entry = new bcoin.chainblock(this, {
+    entry = new bcoin.chainblock(self, {
       hash: hash,
       version: block.version,
       prevBlock: prevHash,
@@ -430,9 +530,9 @@ Chain.prototype.add = function add(block, peer) {
 
     // Add entry if we do not have it (or if
     // there is another entry at its height)
-    existing = this.db.get(entry.height);
+    existing = self.db.get(entry.height);
     if (!existing || existing.hash !== hash) {
-      assert(this.heightLookup[entry.hash] == null);
+      assert(self.heightLookup[entry.hash] == null);
 
       // A valid block with an already existing
       // height came in, that spells fork. We
@@ -443,9 +543,9 @@ Chain.prototype.add = function add(block, peer) {
         // The tip has more chainwork, it is a
         // higher height than the entry. This is
         // not an alternate tip. Ignore it.
-        if (this.tip.chainwork.cmp(entry.chainwork) > 0) {
+        if (self.tip.chainwork.cmp(entry.chainwork) > 0) {
           code = Chain.codes.unchanged;
-          break;
+          return done(null, code);
         }
         // Get _our_ tip as opposed to
         // the attempted alternate tip.
@@ -453,57 +553,63 @@ Chain.prototype.add = function add(block, peer) {
         // The block has equal chainwork (an
         // alternate tip). Reset the chain, find
         // a new peer, and wait to see who wins.
-        this.resetHeight(entry.height - 1);
-        this.emit('fork', {
+        self.resetHeight(entry.height - 1);
+        self.emit('fork', {
           height: prevHeight + 1,
           expected: tip.hash,
           received: hash,
           checkpoint: false
         }, peer);
         code = Chain.codes.forked;
-        break;
+        return self._removeBlock(tip.hash, function(err) {
+          if (err)
+            return done(err);
+          return done(null, code);
+        });
       }
 
-      // Do "contextual" verification on our block
-      // now that we're certain its previous
-      // block is in the chain.
-      if (!block.verifyContext()) {
-        code = Chain.codes.invalid;
-        this.emit('invalid', {
-          height: prevHeight + 1,
-          hash: hash
-        }, peer);
-        break;
-      }
-
-      // Attempt to add block to the chain index.
-      code = this._addEntry(entry);
-
-      // Result should never be `unchanged` since
-      // we already verified there were no
-      // duplicate heights, etc.
-      assert(code !== Chain.codes.unchanged);
-
+      // Fork at checkpoint
       // Block did not match the checkpoint. The
       // chain could be reset to the last sane
       // checkpoint, but it really isn't necessary,
       // so we don't do it. The misbehaving peer has
       // been killed and hopefully we find a peer
       // who isn't trying to fool us.
-      if (code === Chain.codes.badCheckpoint) {
-        this.emit('fork', {
-          height: entry.height,
-          expected: network.checkpoints[entry.height],
-          received: entry.hash,
-          checkpoint: true
-        });
-        break;
+      checkpoint = network.checkpoints[entry.height];
+      if (checkpoint) {
+        self.emit('checkpoint', entry.height, entry.hash, checkpoint);
+        if (hash !== checkpoint) {
+          // Resetting to the last checkpoint _really_ isn't
+          // necessary (even bitcoind doesn't do it), but it
+          // could be used if you want to be on the overly
+          // safe (see: paranoid) side.
+          // this.resetLastCheckpoint(entry.height);
+          code = Chain.codes.badCheckpoint;
+          self.emit('fork', {
+            height: entry.height,
+            expected: network.checkpoints[entry.height],
+            received: entry.hash,
+            checkpoint: true
+          });
+          return done(null, code);
+        }
       }
 
-      // Should never happen, but... something
-      // went wrong. Ignore this block.
-      if (code !== Chain.codes.okay)
-        break;
+      // Could fill here for contextual verification.
+      // Also check isSpent here!
+      // self._fillCoins(block, function(err) {
+
+      // Do "contextual" verification on our block
+      // now that we're certain its previous
+      // block is in the chain.
+      if (!block.verifyContext()) {
+        code = Chain.codes.invalid;
+        self.emit('invalid', {
+          height: prevHeight + 1,
+          hash: hash
+        }, peer);
+        return done(null, code);
+      }
 
       // Update the block height
       block.height = entry.height;
@@ -511,50 +617,79 @@ Chain.prototype.add = function add(block, peer) {
         tx.height = entry.height;
       });
 
-      // Keep track of the number of blocks we
-      // added and the number of orphans resolved.
-      total++;
+      // Attempt to add block to the chain index.
+      self._addEntry(entry, block, function(err, code_) {
+        if (err)
+          return done(err);
 
-      // Emit our block (and potentially resolved
-      // orphan) so the programmer can save it.
-      this.emit('block', block, peer);
-      this.emit('entry', entry);
-      if (block !== initial)
-        this.emit('resolved', block, peer);
+        code = code_;
 
-      // Fullfill request
-      this.request.fullfill(hash, block);
+        // Result should never be `unchanged` since
+        // we already verified there were no
+        // duplicate heights, etc.
+        assert(code !== Chain.codes.unchanged);
+
+        // Should always be okay.
+        assert(code === Chain.codes.okay);
+
+        // Keep track of the number of blocks we
+        // added and the number of orphans resolved.
+        total++;
+
+        // Emit our block (and potentially resolved
+        // orphan) so the programmer can save it.
+        self.emit('block', block, peer);
+        self.emit('entry', entry);
+        if (block !== initial)
+          self.emit('resolved', block, peer);
+
+        // Fullfill request
+        self.request.fullfill(hash, block);
+
+        handleOrphans();
+      });
+    } else {
+      handleOrphans();
     }
 
-    if (!this.orphan.map[hash])
-      break;
+    function handleOrphans() {
+      if (!self.orphan.map[hash])
+        return done(null, code);
 
-    // An orphan chain was found, start resolving.
-    block = this.orphan.map[hash];
-    delete this.orphan.bmap[block.hash('hex')];
-    delete this.orphan.map[hash];
-    this.orphan.count--;
-    this.orphan.size -= block.getSize();
+      // An orphan chain was found, start resolving.
+      block = self.orphan.map[hash];
+      delete self.orphan.bmap[block.hash('hex')];
+      delete self.orphan.map[hash];
+      self.orphan.count--;
+      self.orphan.size -= block.getSize();
+
+      next();
+    }
+  })();
+
+  function done(err, code) {
+    // Failsafe for large orphan chains. Do not
+    // allow more than 20mb stored in memory.
+    if (self.orphan.size > 20971520) {
+      Object.keys(self.orphan.bmap).forEach(function(hash) {
+        self.emit('unresolved', self.orphan.bmap[hash], peer);
+      });
+      self.orphan.map = {};
+      self.orphan.bmap = {};
+      self.orphan.count = 0;
+      self.orphan.size = 0;
+    }
+
+    if (code !== Chain.codes.okay) {
+      if (!(self.options.multiplePeers && code === Chain.codes.newOrphan))
+        utils.debug('Chain Error: %s', Chain.msg(code));
+    }
+
+    if (err)
+      return callback(err);
+
+    return callback(null, total);
   }
-
-  // Failsafe for large orphan chains. Do not
-  // allow more than 20mb stored in memory.
-  if (this.orphan.size > 20971520) {
-    Object.keys(this.orphan.bmap).forEach(function(hash) {
-      this.emit('unresolved', this.orphan.bmap[hash], peer);
-    }, this);
-    this.orphan.map = {};
-    this.orphan.bmap = {};
-    this.orphan.count = 0;
-    this.orphan.size = 0;
-  }
-
-  if (code !== Chain.codes.okay) {
-    if (!(this.options.multiplePeers && code === Chain.codes.newOrphan))
-      utils.debug('Chain Error: %s', Chain.msg(code));
-  }
-
-  return total;
 };
 
 Chain.prototype.has = function has(hash) {
diff --git a/lib/bcoin/chaindb.js b/lib/bcoin/chaindb.js
index c3b6b702..9be887f4 100644
--- a/lib/bcoin/chaindb.js
+++ b/lib/bcoin/chaindb.js
@@ -222,8 +222,8 @@ ChainDB.prototype.getAsync = function getAsync(height, callback) {
   });
 };
 
-ChainDB.prototype.save = function save(entry) {
-  return this.saveAsync(entry);
+ChainDB.prototype.save = function save(entry, callback) {
+  return this.saveAsync(entry, callback);
 };
 
 ChainDB.prototype.saveSync = function saveSync(entry) {
diff --git a/lib/bcoin/node.js b/lib/bcoin/node.js
index a4ea2542..dc52df8e 100644
--- a/lib/bcoin/node.js
+++ b/lib/bcoin/node.js
@@ -60,6 +60,12 @@ Node.prototype._init = function _init() {
   this.pool = new bcoin.pool(this.options.pool);
   this.chain = this.pool.chain;
 
+  if (0)
+  this.pool.on('block', function(block, peer) {
+    self.mempool.addBlock(block);
+  });
+
+  if (0)
   this.pool.on('block', function(block, peer) {
     self.block.saveBlock(block, function(err) {
       if (err)
@@ -93,6 +99,12 @@ Node.prototype._init = function _init() {
     self.emit('error', err);
   });
 
+  this.pool.on('fork', function(data) {
+    if (data.block)
+      self.mempool.removeBlock(block);
+  });
+
+  if (0)
   this.pool.on('fork', function(a, b) {
     [a, b].forEach(function(hash) {
       self.block.removeBlock(hash, function(err, block) {
diff --git a/lib/bcoin/pool.js b/lib/bcoin/pool.js
index c330648a..26bc0df1 100644
--- a/lib/bcoin/pool.js
+++ b/lib/bcoin/pool.js
@@ -380,10 +380,15 @@ Pool.prototype._addLoader = function _addLoader() {
       return;
     // If the peer sent us a block that was added
     // to the chain (not orphans), reset the timeout.
-    if (self._handleBlock(block, peer)) {
-      self._startInterval();
-      self._startTimer();
-    }
+    self._handleBlock(block, peer, function(err, added) {
+      if (err)
+        self.emit('error', err);
+
+      if (added) {
+        self._startInterval();
+        self._startTimer();
+      }
+    });
   });
 
   peer.on('block', function(block) {
@@ -391,10 +396,15 @@ Pool.prototype._addLoader = function _addLoader() {
       return;
     // If the peer sent us a block that was added
     // to the chain (not orphans), reset the timeout.
-    if (self._handleBlock(block, peer)) {
-      self._startInterval();
-      self._startTimer();
-    }
+    self._handleBlock(block, peer, function(err, added) {
+      if (err)
+        self.emit('error', err);
+
+      if (added) {
+        self._startInterval();
+        self._startTimer();
+      }
+    });
   });
 
   if (self.options.headers) {
@@ -590,126 +600,152 @@ Pool.prototype._prehandleBlock = function _prehandleBlock(block, peer, callback)
   return callback(null, block);
 };
 
-Pool.prototype._handleBlock = function _handleBlock(block, peer) {
+Pool.prototype._handleBlock = function _handleBlock(block, peer, callback) {
   var self = this;
-  var requested;
 
-  // Fulfill our request.
-  requested = this._response(block);
+  callback = utils.asyncify(callback);
 
-  // Emulate BIP37: emit all the filtered transactions.
-  if (this.options.fullNode && this.listeners('watched').length > 0) {
-    block.txs.forEach(function(tx) {
-      if (self.isWatched(tx))
-        self.emit('watched', tx, peer);
+  this._prehandleBlock(block, peer, function(err) {
+    var requested;
+
+    if (err)
+      return callback(err);
+
+    // Fulfill our request.
+    requested = self._response(block);
+
+    // Emulate BIP37: emit all the filtered transactions.
+    if (self.options.fullNode && self.listeners('watched').length > 0) {
+      block.txs.forEach(function(tx) {
+        if (self.isWatched(tx))
+          self.emit('watched', tx, peer);
+      });
+    }
+
+    // Ensure the block was not invalid last time.
+    // Someone might be sending us bad blocks to DoS us.
+    if (self.block.invalid[block.hash('hex')]) {
+      utils.debug('Peer is sending an invalid chain (%s)', peer.host);
+      self.setMisbehavior(peer, 100);
+      return callback(null, false);
+    }
+
+    // Ensure this is not a continuation
+    // of an invalid chain.
+    if (self.block.invalid[block.prevBlock]) {
+      utils.debug(
+        'Peer is sending an invalid continuation chain (%s)',
+        peer.host);
+      self.setMisbehavior(peer, 100);
+      return callback(null, false);
+    }
+
+    // Ignore if we already have.
+    if (self.chain.has(block)) {
+      utils.debug('Already have block %s (%s)', block.height, peer.host);
+      self.setMisbehavior(peer, 1);
+      return callback(null, false);
+    }
+
+    // Make sure the block is valid.
+    if (!block.verify()) {
+      utils.debug(
+        'Block verification failed for %s (%s)',
+        block.rhash, peer.host);
+      self.block.invalid[block.hash('hex')] = true;
+      self.setMisbehavior(peer, 100);
+      return callback(null, false);
+    }
+
+    // Someone is sending us blocks without
+    // us requesting them.
+    if (!requested) {
+      utils.debug(
+        'Recieved unrequested block: %s (%s)',
+        block.rhash, peer.host);
+    }
+
+    // Resolve orphan chain
+    if (!self.options.headers) {
+      if (!self.chain.hasBlock(block.prevBlock)) {
+        // Special case for genesis block.
+        if (block.isGenesis())
+          return callback(null, false);
+
+        // Make sure the peer doesn't send us
+        // more than 200 orphans every 3 minutes.
+        if (self.isOrphaning(peer)) {
+          utils.debug('Peer is orphaning (%s)', peer.host);
+          self.setMisbehavior(peer, 100);
+          return callback(null, false);
+        }
+
+        // NOTE: If we were to emit new orphans here, we
+        // would not need to store full blocks as orphans.
+        // However, the listener would not be able to see
+        // the height until later.
+        self._addIndex(block, peer, function(err, added) {
+          if (err)
+            return callback(err);
+
+          if (added)
+            self.emit('pool block', block, peer);
+
+          // Resolve orphan chain.
+          self.peers.load.loadBlocks(
+            self.chain.getLocator(),
+            self.chain.getOrphanRoot(block)
+          );
+
+          utils.debug('Handled orphan %s (%s)', block.rhash, peer.host);
+
+          return callback(null, false);
+        });
+
+        return;
+      }
+    } else {
+      if (!self.chain.hasBlock(block.prevBlock)) {
+        // Special case for genesis block.
+        if (block.isGenesis())
+          return callback(null, false);
+
+        // Increase banscore by 10 if we're using getheaders.
+        if (!self.options.multiplePeers) {
+          if (self.setMisbehavior(peer, 10))
+            return callback(null, false);
+        }
+      }
+    }
+
+    // Add to index and emit/save
+    self._addIndex(block, peer, function(err, added) {
+      if (err)
+        return callback(err);
+
+      if (added) {
+        self.emit('pool block', block, peer);
+        return callback(null, true);
+      }
+
+      return callback(null, false);
     });
-  }
-
-  // Ensure the block was not invalid last time.
-  // Someone might be sending us bad blocks to DoS us.
-  if (this.block.invalid[block.hash('hex')]) {
-    utils.debug('Peer is sending an invalid chain (%s)', peer.host);
-    this.setMisbehavior(peer, 100);
-    return false;
-  }
-
-  // Ensure this is not a continuation
-  // of an invalid chain.
-  if (this.block.invalid[block.prevBlock]) {
-    utils.debug(
-      'Peer is sending an invalid continuation chain (%s)',
-      peer.host);
-    this.setMisbehavior(peer, 100);
-    return false;
-  }
-
-  // Ignore if we already have.
-  if (this.chain.has(block)) {
-    utils.debug('Already have block %s (%s)', block.height, peer.host);
-    this.setMisbehavior(peer, 1);
-    return false;
-  }
-
-  // Make sure the block is valid.
-  if (!block.verify()) {
-    utils.debug(
-      'Block verification failed for %s (%s)',
-      block.rhash, peer.host);
-    this.block.invalid[block.hash('hex')] = true;
-    this.setMisbehavior(peer, 100);
-    return false;
-  }
-
-  // Someone is sending us blocks without
-  // us requesting them.
-  if (!requested) {
-    utils.debug(
-      'Recieved unrequested block: %s (%s)',
-      block.rhash, peer.host);
-  }
-
-  // Resolve orphan chain
-  if (!this.options.headers) {
-    if (!this.chain.hasBlock(block.prevBlock)) {
-      // Special case for genesis block.
-      if (block.isGenesis())
-        return false;
-
-      // Make sure the peer doesn't send us
-      // more than 200 orphans every 3 minutes.
-      if (this.isOrphaning(peer)) {
-        utils.debug('Peer is orphaning (%s)', peer.host);
-        this.setMisbehavior(peer, 100);
-        return false;
-      }
-
-      // NOTE: If we were to emit new orphans here, we
-      // would not need to store full blocks as orphans.
-      // However, the listener would not be able to see
-      // the height until later.
-      if (this._addIndex(block, peer))
-        this.emit('pool block', block, peer);
-
-      // Resolve orphan chain.
-      this.peers.load.loadBlocks(
-        this.chain.getLocator(),
-        this.chain.getOrphanRoot(block)
-      );
-
-      utils.debug('Handled orphan %s (%s)', block.rhash, peer.host);
-
-      return false;
-    }
-  } else {
-    if (!this.chain.hasBlock(block.prevBlock)) {
-      // Special case for genesis block.
-      if (block.isGenesis())
-        return false;
-
-      // Increase banscore by 10 if we're using getheaders.
-      if (!this.options.multiplePeers) {
-        if (this.setMisbehavior(peer, 10))
-          return false;
-      }
-    }
-  }
-
-  // Add to index and emit/save
-  if (this._addIndex(block, peer)) {
-    this.emit('pool block', block, peer);
-    return true;
-  }
+  });
 };
 
-Pool.prototype._addIndex = function _addIndex(block, peer) {
-  var added = this.chain.add(block, peer);
+Pool.prototype._addIndex = function _addIndex(block, peer, callback) {
+  var self = this;
+  this.chain.add(block, peer, function(err, added) {
+    if (err)
+      return callback(err);
 
-  if (added === 0)
-    return false;
+    if (added === 0)
+      return callback(null, false);
 
-  this.emit('chain-progress', this.chain.fillPercent(), peer);
+    self.emit('chain-progress', self.chain.fillPercent(), peer);
 
-  return true;
+    return callback(null, true);
+  });
 };
 
 Pool.prototype.isFull = function isFull() {
@@ -816,15 +852,28 @@ Pool.prototype._createPeer = function _createPeer(options) {
   return peer;
 };
 
-Pool.prototype._handleTX = function _handleTX(tx, peer) {
-  var requested = this._response(tx);
-  var added = this._addTX(tx, 1);
+Pool.prototype._handleTX = function _handleTX(tx, peer, callback) {
+  var self = this;
 
-  if (added || tx.block)
-    this.emit('tx', tx, peer);
+  callback = utils.asyncify(callback);
 
-  if (!this.options.fullNode && tx.block)
-    this.emit('watched', tx, peer);
+  this._prehandleTX(tx, peer, function(err) {
+    var requested, added;
+
+    if (err)
+      return callback(err);
+
+    requested = self._response(tx);
+    added = self._addTX(tx, 1);
+
+    if (added || tx.block)
+      self.emit('tx', tx, peer);
+
+    if (!self.options.fullNode && tx.block)
+      self.emit('watched', tx, peer);
+
+    return callback();
+  });
 };
 
 Pool.prototype._addLeech = function _addLeech(socket) {
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index e64574f6..e818a678 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -419,7 +419,9 @@ RequestCache.prototype.fullfill = function fullfill(id, err, data) {
 utils.RequestCache = RequestCache;
 
 utils.asyncify = function asyncify(fn) {
-  return function _asynicifedFn(err, data1, data2) {
+  if (fn && fn.name === '_asyncifiedFn')
+    return fn;
+  return function _asyncifiedFn(err, data1, data2) {
     if (!fn)
       return err || data1;
     utils.nextTick(function() {