fix: ensure uTP peer address is IPv4 (#2125)

lib/torrent.js

@@ -762,8 +762,9 @@ class Torrent extends EventEmitter {
     if (this.destroyed) throw new Error('torrent is destroyed')
     if (!this.infoHash) throw new Error('addPeer() must not be called before the `infoHash` event')
 
+    let host
+
     if (this.client.blocked) {
-      let host
       if (typeof peer === 'string') {
         let parts
         try {
@@ -787,7 +788,10 @@ class Torrent extends EventEmitter {
     }
 
     // if the utp connection fails to connect, then it is replaced with a tcp connection to the same ip:port
-    const wasAdded = !!this._addPeer(peer, this.client.utp ? 'utp' : 'tcp')
+
+    const type = (this.client.utp && this._isIPv4(host)) ? 'utp' : 'tcp'
+    const wasAdded = !!this._addPeer(peer, type)
+
     if (wasAdded) {
       this.emit('peer', peer)
     } else {
@@ -1800,7 +1804,9 @@ class Torrent extends EventEmitter {
 
       const reconnectTimeout = setTimeout(() => {
         if (this.destroyed) return
-        const newPeer = this._addPeer(peer.addr, this.client.utp ? 'utp' : 'tcp')
+        const host = addrToIPPort(peer.addr)[0]
+        const type = (this.client.utp && this._isIPv4(host)) ? 'utp' : 'tcp'
+        const newPeer = this._addPeer(peer.addr, type)
         if (newPeer) newPeer.retries = peer.retries + 1
       }, ms)
       if (reconnectTimeout.unref) reconnectTimeout.unref()
@@ -1824,6 +1830,16 @@ class Torrent extends EventEmitter {
     return port > 0 && port < 65535 &&
       !(host === '127.0.0.1' && port === this.client.torrentPort)
   }
+
+  /**
+   * Return `true` if string is a valid IPv4 address.
+   * @param {string} addr
+   * @return {boolean}
+   */
+  _isIPv4 (addr) {
+    const IPv4Pattern = /^((?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])[.]){3}(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$/
+    return IPv4Pattern.test(addr)
+  }
 }
 
 function getBlockPipelineLength (wire, duration) {

test/node/conn-pool.js

@@ -100,6 +100,54 @@ test('client.conn-pool: use uTP when uTP enabled', function (t) {
   })
 })
 
+test('client.conn-pool: adding IPv6 peer when uTP enabled should fallback to TCP', function (t) {
+  t.plan(6)
+
+  const client1 = new WebTorrent({ dht: false, tracker: false, lsd: false, utp: true })
+  const client2 = new WebTorrent({ dht: false, tracker: false, lsd: false, utp: true })
+
+  client1.on('error', function (err) { t.fail(err) })
+  client1.on('warning', function (err) { t.fail(err) })
+
+  client2.on('error', function (err) { t.fail(err) })
+  client2.on('warning', function (err) { t.fail(err) })
+
+  // Start seeding
+  client2.seed(fixtures.leaves.content, {
+    name: 'Leaves of Grass by Walt Whitman.epub',
+    announce: []
+  })
+
+  client2.on('listening', function () {
+    // Start downloading
+    const torrent = client1.add(fixtures.leaves.parsedTorrent.infoHash, { store: MemoryChunkStore })
+
+    // Manually connect peers
+    torrent.addPeer('[::1]:' + client2.address().port)
+
+    let order = 0
+
+    torrent.on('infoHash', function () {
+      t.equal(++order, 1)
+    })
+
+    torrent.on('metadata', function () {
+      t.equal(++order, 2)
+    })
+
+    torrent.on('ready', function () {
+      t.equal(++order, 3)
+    })
+
+    torrent.on('done', function () {
+      t.equal(++order, 4)
+
+      client1.destroy(function (err) { t.error(err, 'client 1 destroyed') })
+      client2.destroy(function (err) { t.error(err, 'client 2 destroyed') })
+    })
+  })
+})
+
 // Warning: slow test as we need to rely on connection timeouts
 test('client.conn-pool: fallback to TCP when uTP server failed', function (t) {
   t.plan(6)