fix: add x-forwarded-* headers (#56797)

### What?

Adding back `x-forwarded-*` headers.


### Why?

Starting with #52492, these headers were lost.

### How?

We can populate these headers before executing a request.

Closes NEXT-1663
Fixes #55942

packages/next/src/server/lib/router-server.ts

@@ -33,6 +33,7 @@ import {
   PERMANENT_REDIRECT_STATUS,
 } from '../../shared/lib/constants'
 import { DevBundlerService } from './dev-bundler-service'
+import type { TLSSocket } from 'tls'
 
 const debug = setupDebug('next:router-server:main')
 
@@ -222,6 +223,17 @@ export async function initialize(opts: {
         'x-middleware-invoke': '',
         'x-invoke-path': invokePath,
         'x-invoke-query': encodeURIComponent(JSON.stringify(parsedUrl.query)),
+        'x-forwarded-host':
+          req.headers['x-forwarded-host'] ?? req.headers.host ?? opts.hostname,
+        'x-forwarded-port':
+          req.headers['x-forwarded-port'] ?? opts.port.toString(),
+        'x-forwarded-proto':
+          req.headers['x-forwarded-proto'] ??
+          (req.socket as TLSSocket).encrypted
+            ? 'https'
+            : 'http',
+        'x-forwarded-for':
+          req.headers['x-forwarded-for'] ?? req.socket.remoteAddress,
         ...(additionalInvokeHeaders || {}),
       }
       Object.assign(req.headers, invokeHeaders)

test/e2e/app-dir/x-forwarded-headers/app/route.tsx

@@ -0,0 +1,3 @@
+export function GET(req: Request) {
+  return Response.json(Object.fromEntries(req.headers))
+}

test/e2e/app-dir/x-forwarded-headers/x-forwarded-headers.test.ts

@@ -0,0 +1,13 @@
+import { createNextDescribe } from 'e2e-utils'
+
+createNextDescribe('x-forwarded-headers', { files: __dirname }, ({ next }) => {
+  it('should include x-forwarded-* headers', async () => {
+    const res = await next.fetch('/')
+    const headers = await res.json()
+    const url = new URL(next.url)
+    expect(headers['x-forwarded-host']).toBe(url.host)
+    expect(headers['x-forwarded-port']).toBe(url.port)
+    expect(headers['x-forwarded-proto']).toBe(url.protocol.replace(':', ''))
+    console.log(headers)
+  })
+})