From fd2f15816964fb587aedfbce99918072ca15d753 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Sat, 14 Jan 2017 06:43:49 -0800
Subject: [PATCH] net: avoid requesting duplicate blocks. avoid reconnecting to
 banned peers.

---
 lib/blockchain/chain.js | 25 ++++++++++++++++++++++++-
 lib/net/pool.js         | 28 ++++++++++++++++++----------
 2 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index 5652eca8..d3a57f00 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -1583,7 +1583,8 @@ Chain.prototype.removeInvalid = function removeInvalid(hash) {
 };
 
 /**
- * Test the chain to see if it has a block, orphan, or pending block.
+ * Test the chain to see if it contains
+ * a block, or has recently seen a block.
  * @param {Hash} hash
  * @returns {Promise} - Returns Boolean.
  */
@@ -1595,9 +1596,31 @@ Chain.prototype.has = co(function* has(hash) {
   if (this.locker.has(hash))
     return true;
 
+  if (this.invalid.has(hash))
+    return true;
+
   return yield this.hasEntry(hash);
 });
 
+/**
+ * Test the chain to see if it has recently seen a block.
+ * @param {Hash} hash
+ * @returns {Boolean}
+ */
+
+Chain.prototype.seen = function seen(hash) {
+  if (this.hasOrphan(hash))
+    return true;
+
+  if (this.locker.has(hash))
+    return true;
+
+  if (this.invalid.has(hash))
+    return true;
+
+  return this.db.hasCache(hash);
+};
+
 /**
  * Find a block entry by timestamp.
  * @param {Number} ts - Timestamp.
diff --git a/lib/net/pool.js b/lib/net/pool.js
index 70fd2968..359da4d0 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -879,17 +879,15 @@ Pool.prototype.handleOpen = function handleOpen(peer) {
  */
 
 Pool.prototype.handleClose = co(function* handleClose(peer, connected) {
-  var loader = peer.isLoader();
+  var outbound = peer.outbound;
 
   this.removePeer(peer);
 
   if (!this.loaded)
     return;
 
-  if (!loader) {
-    this.refill();
+  if (!outbound)
     return;
-  }
 
   this.refill();
 });
@@ -1427,10 +1425,13 @@ Pool.prototype.getHost = function getHost(unique) {
     if (!addr.hasServices(this.reqServices))
       continue;
 
-    if (now - entry.lastAttempt < 600 && i < 30)
+    if (i < 30 && now - entry.lastAttempt < 600)
       continue;
 
-    if (addr.port !== this.network.port && i < 50)
+    if (i < 50 && addr.port !== this.network.port)
+      continue;
+
+    if (i < 95 && this.hosts.isBanned(addr.host))
       continue;
 
     return entry.addr;
@@ -1820,22 +1821,29 @@ Pool.prototype.sendBlockRequests = function sendBlockRequests(peer) {
   for (i = 0; i < queue.length; i++) {
     hash = queue[i];
 
+    if (hashes.length === size)
+      break;
+
     assert(this.queueMap.has(hash));
 
     this.queueMap.remove(hash);
 
     assert(!this.requestMap.has(hash));
 
+    // Do a second check to make sure
+    // we don't have this in the chain.
+    // Avoids a potential race condition
+    // with the `chain.has()` call.
+    if (this.chain.seen(hash))
+      continue;
+
     this.requestMap.insert(hash);
     peer.requestMap.insert(hash);
 
     hashes.push(hash);
-
-    if (hashes.length === size)
-      break;
   }
 
-  peer.blockQueue = queue.slice(hashes.length);
+  peer.blockQueue = queue.slice(i);
 
   this.logger.debug(
     'Requesting %d/%d blocks from peer with getdata (%s).',