Fix FS drops connection if download is too slow

Only happens in HTTPS because seemingly somewhere in the stack up to
50mb of data is being buffered potentially triggering a timeout at a
higher level if not drained fast enough.

This commit also includes other streams related improvements.

lib/cwmp.ts

@@ -48,7 +48,7 @@ import {
   CpeFault,
 } from "./types";
 import { IncomingMessage, ServerResponse } from "http";
-import { Readable } from "stream";
+import { pipeline, Readable } from "stream";
 import { promisify } from "util";
 import { decode, encodingExists } from "iconv-lite";
 import { parseXmlDeclaration } from "./xml-parser";
@@ -1451,10 +1451,14 @@ async function listenerAsync(
   if (httpRequest.headers["content-encoding"]) {
     switch (httpRequest.headers["content-encoding"]) {
       case "gzip":
-        stream = httpRequest.pipe(zlib.createGunzip());
+        stream = pipeline(stream, zlib.createGunzip(), () => {
+          // Errors are also raised by the async iterator
+        });
         break;
       case "deflate":
-        stream = httpRequest.pipe(zlib.createInflate());
+        stream = pipeline(stream, zlib.createInflate(), () => {
+          // Errors are also raised by the async iterator
+        });
         break;
       default:
         httpResponse.writeHead(415, { Connection: "close" });
@@ -1463,34 +1467,17 @@ async function listenerAsync(
     }
   }
 
-  const body = await new Promise<Buffer>((resolve, reject) => {
-    const chunks: Buffer[] = [];
-    let bytes = 0;
+  const chunks: Buffer[] = [];
+  try {
+    for await (const chunk of stream) chunks.push(chunk);
+    // In Node versions prior to 15, the stream will not emit an error if the
+    // connection is closed before the stream is finished.
+    if (!stream.readableEnded) throw new Error("Connection closed");
+  } catch (err) {
+    return;
+  }
 
-    stream.on("data", (chunk) => {
-      chunks.push(chunk);
-      bytes += chunk.length;
-    });
-
-    stream.on("end", () => {
-      const _body = Buffer.allocUnsafe(bytes);
-      let offset = 0;
-      for (const chunk of chunks) {
-        chunk.copy(_body, offset, 0, chunk.length);
-        offset += chunk.length;
-      }
-      resolve(_body);
-    });
-
-    stream.on("error", reject);
-
-    httpRequest.on("aborted", () => {
-      resolve(null);
-    });
-  });
-
-  // Request aborted
-  if (!body) return;
+  const body = Buffer.concat(chunks);
 
   let sessionContext = currentSessions.get(httpRequest.socket);