Drop ipc server headers filters

packages/next/src/server/lib/router-utils/resolve-routes.ts

@@ -9,7 +9,6 @@ import url from 'url'
 import { Redirect } from '../../../../types'
 import setupDebug from 'next/dist/compiled/debug'
 import { getCloneableBody } from '../../body-streams'
-import { filterReqHeaders, ipcForbiddenHeaders } from '../server-ipc/utils'
 import { Header } from '../../../lib/load-custom-routes'
 import { stringifyQuery } from '../../server-route-utils'
 import { formatHostname } from '../format-hostname'
@@ -457,7 +456,7 @@ export function getResolveRoutes(
               const { res: mockedRes } = await createRequestResponseMocks({
                 url: req.url || '/',
                 method: req.method || 'GET',
-                headers: filterReqHeaders(invokeHeaders, ipcForbiddenHeaders),
+                headers: invokeHeaders,
                 resWriter(chunk) {
                   readableController.enqueue(Buffer.from(chunk))
                   return true
@@ -560,7 +559,7 @@ export function getResolveRoutes(
             delete middlewareHeaders['x-middleware-next']
 
             for (const [key, value] of Object.entries({
-              ...filterReqHeaders(middlewareHeaders, ipcForbiddenHeaders),
+              ...middlewareHeaders,
             })) {
               if (
                 [

packages/next/src/server/lib/server-ipc/invoke-request.ts

@@ -1,6 +1,5 @@
 import type { IncomingMessage } from 'http'
 import type { Readable } from 'stream'
-import { filterReqHeaders, ipcForbiddenHeaders } from './utils'
 
 export const invokeRequest = async (
   targetUrl: string,
@@ -11,13 +10,10 @@ export const invokeRequest = async (
   },
   readableBody?: Readable | ReadableStream
 ) => {
-  const invokeHeaders = filterReqHeaders(
-    {
-      'cache-control': '',
-      ...requestInit.headers,
-    },
-    ipcForbiddenHeaders
-  ) as IncomingMessage['headers']
+  const invokeHeaders = {
+    'cache-control': '',
+    ...requestInit.headers,
+  }
 
   return await fetch(targetUrl, {
     headers: invokeHeaders as any as Headers,

packages/next/src/server/lib/server-ipc/utils.ts

@@ -1,4 +1,4 @@
-export const ipcForbiddenHeaders = [
+export const actionsForbiddenHeaders = [
   'accept-encoding',
   'keepalive',
   'keep-alive',
@@ -8,10 +8,7 @@ export const ipcForbiddenHeaders = [
   'connection',
   // marked as unsupported by undici: https://github.com/nodejs/undici/blob/c83b084879fa0bb8e0469d31ec61428ac68160d5/lib/core/request.js#L354
   'expect',
-]
-
-export const actionsForbiddenHeaders = [
-  ...ipcForbiddenHeaders,
+  // action specific
   'content-length',
 ]
 

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

@@ -93,7 +93,6 @@ import { nodeFs } from './lib/node-fs-methods'
 import { getRouteRegex } from '../shared/lib/router/utils/route-regex'
 import { invokeRequest } from './lib/server-ipc/invoke-request'
 import { pipeReadable } from './pipe-readable'
-import { filterReqHeaders, ipcForbiddenHeaders } from './lib/server-ipc/utils'
 import { createRequestResponseMocks } from './lib/mock-request'
 import { NEXT_RSC_UNION_QUERY } from '../client/components/app-router-headers'
 import { signalFromNodeResponse } from './web/spec-extension/adapters/next-request'
@@ -539,13 +538,12 @@ export default class NextNodeServer extends BaseServer {
               signal: signalFromNodeResponse(res.originalResponse),
             }
           )
-          const filteredResHeaders = filterReqHeaders(
-            toNodeOutgoingHttpHeaders(invokeRes.headers),
-            ipcForbiddenHeaders
+          const nodeOutgoingHttpHeaders = toNodeOutgoingHttpHeaders(
+            invokeRes.headers
           )
 
-          for (const key of Object.keys(filteredResHeaders)) {
-            newRes.setHeader(key, filteredResHeaders[key] || '')
+          for (const key of Object.keys(nodeOutgoingHttpHeaders)) {
+            newRes.setHeader(key, nodeOutgoingHttpHeaders[key] || '')
           }
           newRes.statusCode = invokeRes.status || 200