From f52e924cda59173ef63dd2635034fd954d09ce7e Mon Sep 17 00:00:00 2001
From: kilpatty <seanpkilgarriff@gmail.com>
Date: Sat, 6 Jul 2019 13:43:11 -0500
Subject: [PATCH] net-pool: Check outbound peers for same group before
 connecting

This commit checks the outbound peers to see which group their network
addresses lives in before connecting. By doing this, we prevent a node
from connecting to all outbound addresses in a very close network group
bunch. This helps prevent someone spinning up multiple nodes on a
similar network e.g. AWS, GCP and using those to fill other nodes'
outbounds.

This commit just adds 2 operations in both addOutbound and addLoader. It
first checks if the new address pull from hostlist belongs in the same
group as an already connected peer. If it does not, it precedes as
usual, and if the connection succeeds then it adds that new outbound
group to the list of groups currently connected to.

Co-authored-by: Nodari Chkuaselidze <nodar.chkuaselidze@gmail.com>
---
 lib/net/pool.js             | 12 +++++++++++-
 test/net-netaddress-test.js |  9 +++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/net/pool.js b/lib/net/pool.js
index 90bb6270..2c4d2f32 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -10,7 +10,6 @@ const assert = require('bsert');
 const EventEmitter = require('events');
 const {Lock} = require('bmutex');
 const IP = require('binet');
-const dns = require('bdns');
 const tcp = require('btcp');
 const UPNP = require('bupnp');
 const socks = require('bsocks');
@@ -85,6 +84,7 @@ class Pool extends EventEmitter {
     this.pendingFilter = null;
     this.refillTimer = null;
     this.discoverTimer = null;
+    this.connectedGroups = new Set();
 
     this.checkpoints = false;
     this.headerChain = new List();
@@ -663,6 +663,7 @@ class Pool extends EventEmitter {
     this.logger.info('Adding loader peer (%s).', peer.hostname());
 
     this.peers.add(peer);
+    this.connectedGroups.add(addr.getGroup());
 
     this.setLoader(peer);
   }
@@ -3367,6 +3368,7 @@ class Pool extends EventEmitter {
 
       if (!entry)
         break;
+
       const addr = entry.addr;
 
       if (this.peers.has(addr.hostname))
@@ -3390,6 +3392,10 @@ class Pool extends EventEmitter {
       if (this.options.brontideOnly && !addr.hasKey())
         continue;
 
+      // Don't connect to outbound peers in the same group.
+      if (this.connectedGroups.has(addr.getGroup()))
+        continue;
+
       if (i < pc30 && now - entry.lastAttempt < 600)
         continue;
 
@@ -3428,6 +3434,7 @@ class Pool extends EventEmitter {
     const peer = this.createOutbound(addr);
 
     this.peers.add(peer);
+    this.connectedGroups.add(addr.getGroup());
 
     this.emit('peer', peer);
   }
@@ -3482,6 +3489,9 @@ class Pool extends EventEmitter {
   removePeer(peer) {
     this.peers.remove(peer);
 
+    if (peer.outbound)
+      this.connectedGroups.delete(peer.address.getGroup());
+
     for (const hash of peer.blockMap.keys())
       this.resolveBlock(peer, hash);
 
diff --git a/test/net-netaddress-test.js b/test/net-netaddress-test.js
index 222d2087..fa4a275b 100644
--- a/test/net-netaddress-test.js
+++ b/test/net-netaddress-test.js
@@ -1,5 +1,14 @@
 'use strict';
 
+/* Parts of this software are based on bitcoin/bitcoin:
+ *   Copyright (c) 2009-2019, The Bitcoin Core Developers (MIT License).
+ *   Copyright (c) 2009-2019, The Bitcoin Developers (MIT License).
+ *   https://github.com/bitcoin/bitcoin
+ *
+ * Resources:
+ *   https://github.com/bitcoin/bitcoin/blob/46fc4d1a24c88e797d6080336e3828e45e39c3fd/src/test/netbase_tests.cpp
+ */
+
 const assert = require('bsert');
 const NetAddress = require('../lib/net/netaddress');
 const Network = require('../lib/protocol/network');