add allowNode that can filter which nodes are added automatically (#46)

* add allowNode that can filter which nodes are added automatically

* Add test and rename option

Co-authored-by: Kasper Isager Dalsgarð <kasperisager@hey.com>

index.js

@@ -56,6 +56,7 @@ class DHT extends EventEmitter {
     this._tickInterval = setInterval(this._ontick.bind(this), TICK_INTERVAL)
     this._lastTick = Date.now()
     this._lastHost = null
+    this._shouldAddNode = opts.addNode || null
     this._onrow = (row) => row.on('full', (node) => this._onfullrow(node, row))
     this._nonePersistentSamples = []
     this._bootstrapping = this._bootstrap()
@@ -241,6 +242,10 @@ class DHT extends EventEmitter {
   }
 
   _addNodeFromNetwork (sample, from, to) {
+    if (this._shouldAddNode !== null && !this._shouldAddNode(from)) {
+      return
+    }
+
     if (from.id === null) {
       this._sampleBootstrapMaybe(from, to)
       return

test.js

@@ -311,6 +311,25 @@ test('relay', async function (t) {
   t.is(res.to.port, a.address().port)
 })
 
+test('filter nodes from routing table', async function (t) {
+  const [a, b, c] = await makeSwarm(3, t)
+
+  const node = new DHT({
+    ephemeral: false,
+    bootstrap: [a],
+    addNode (from) {
+      return from.port !== b.port
+    }
+  })
+
+  t.teardown(() => node.destroy())
+
+  const q = node.findNode(c.id)
+  await q.finished()
+
+  t.absent(node.table.has(b.id), 'should not have b')
+})
+
 function freePort () {
   return new Promise(resolve => {
     const socket = dgram.createSocket('udp4')