fix: improve resiliency of internals _send

package.json

@@ -30,10 +30,10 @@
   "homepage": "https://github.com/libp2p/js-libp2p-mplex#readme",
   "devDependencies": {
     "aegir": "^15.2.0",
-    "chai": "^4.1.2",
+    "chai": "^4.2.0",
     "dirty-chai": "^2.0.1",
     "interface-stream-muxer": "~0.5.9",
-    "libp2p-tcp": "~0.12.0",
+    "libp2p-tcp": "~0.13.0",
     "libp2p-websockets": "~0.12.0",
     "pull-pair": "^1.1.0"
   },
@@ -45,10 +45,10 @@
     "duplexify": "^3.6.0",
     "interface-connection": "~0.3.2",
     "pull-catch": "^1.0.0",
-    "pull-stream": "^3.6.8",
+    "pull-stream": "^3.6.9",
     "pull-stream-to-stream": "^1.3.4",
     "pump": "^3.0.0",
-    "readable-stream": "^2.3.6",
+    "readable-stream": "^3.0.3",
     "stream-to-pull-stream": "^1.7.2",
     "through2": "^2.0.3",
     "varint": "^5.0.0"

src/internals/index.js

@@ -148,7 +148,6 @@ class Multiplex extends stream.Duplex {
   _send (header/* : number */, data /* :: ?: Buffer */)/* : bool */ {
     const len = data ? data.length : 0
     const oldUsed = used
-    let drained = true
 
     this.log('_send', header, len)
 
@@ -157,18 +156,22 @@ class Multiplex extends stream.Duplex {
     varint.encode(len, pool, used)
     used += varint.encode.bytes
 
-    drained = this.push(pool.slice(oldUsed, used))
+    let buf = pool.slice(oldUsed, used)
 
     if (pool.length - used < 100) {
       pool = Buffer.alloc(10 * 1024)
       used = 0
     }
 
-    if (data && drained) {
-      drained = this.push(data)
+    if (data) {
+      buf = Buffer.concat([
+        buf,
+        data
+      ])
     }
 
-    return drained
+    // Push and return the results
+    return this.push(buf)
   }
 
   _addChannel (channel/* : Channel */, id/* : number */, list/* : Array<Channel|null> */)/* : Channel */ {