req.url and req.nextUrl Show Docker Container IP/Port Instead of Real Host

[muradsofi]

Link to the code that reproduces this issue

https://github.com/muradsofi/next-13.5.5-req-issue-demo

To Reproduce

1. Clone the demo repository.

   git clone https://github.com/muradsofi/next-13.5.5-req-issue-demo

2. Build and run the Docker container using the provided Dockerfile.

   a) Build the Docker image

   docker build -t monorepo-demo -f apps/demo/Dockerfile .

   b) Run the Docker container:

   docker run -p 3002:3000 monorepo-demo

3. Access the application in your browser at http://localhost:3002.

4. Log req.url and req.nextUrl in any API route or middleware.

   export default function handler(req, res) { console.log('req.url:', req.url); console.log('req.nextUrl:', req.nextUrl); res.status(200).json({ message: 'Check logs for req.url and req.nextUrl values' }); }

5. Observe the logs to see that req.url and req.nextUrl display the Docker container's IP address and port. (Observation: Even if you run the app on port 3002, you will get port 3000 in req.url.)

6. In the deployed environment, the hostname is displayed as localhost with port docker port 3002.

Current vs. Expected behavior

Current Behavior: req.url and req.nextUrl display the Docker container’s IP address and port.
Expected Behavior: req.url and req.nextUrl should display the actual host URL.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.1.0: Mon Oct  9 21:28:45 PDT 2023; root:xnu-10002.41.9~6/RELEASE_ARM64_T6020
Binaries:
  Node: 18.17.0
  npm: 9.6.7
  Yarn: 1.22.22
  pnpm: 8.14.3
Relevant Packages:
  next: 13.5.6
  eslint-config-next: 13.4.12
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.1.6
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Middleware, Pages Router, Runtime

Which stage(s) are affected? (Select all that apply)

next start (local), Other (Deployed)

Additional context

Deployment Platform: Docker
Issue Started After: Updating to Next.js ^13.5.5