Caddy: Add support for Forwarded header (RFC 7239)

[0az]

RFC 7239 specifies a Forwarded header, which is intended to replace X-Forwarded-*.

It would be great if Caddy supported this.

Ref:

• https://tools.ietf.org/html/rfc7239
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded

[mholt]

Thanks for the request.

What is your use case for this?

The Go team tried to drill down on this a few years ago but the answers were either missing or unsatisfactory: https://github.com/golang/go/issues/20526

[0az]

Thanks for the quick response.

Honestly, it's more of a "nice to have", with a use case of replacing the quasi-standardized X-Forwarded-For/-Host/-Proto/-Scheme. I can afford to do this in my environment (Caddy in front of a small collection of services).

---

Some research on the topic:

I found @c960657's more comprehensive https://c960657.github.io/forwarded.html immediately after I finished making the list below. 😅

Relevant issues/tickets:

• https://bz.apache.org/bugzilla/show_bug.cgi?id=58001
  
  
  
  • ❌ Implemented, not merged
  
  
• https://www.nginx.com/resources/wiki/start/topics/examples/forwarded/
  
  
  
  • ❌ Not implemented, no issue
  
  
• https://github.com/golang/go/issues/20526
  
  
  
  • ❌ Not implemented, issue closed
  
  
• https://github.com/containous/traefik/issues/4099
  
  
  
  • ❌ Implemented, not merged
  
  
• https://github.com/vulcand/oxy/issues/173
  
  
  
  • ❌ Not implemented
  
  
• HAProxy
  
  
  
  • ❌ Not implemented, no issue
  
  
• https://github.com/symfony/symfony/pull/11379
  
  
  
  • ✅ Merged
  
  

[francislavoie]

There's a couple go libs that do the parsing:

• https://github.com/theckman/httpforwarded
• https://github.com/stanvit/go-forwarded

They're both over 4 years old though.

[mholt]

Now _this_ is an excellent feature request. :+1: Not because it's a high priority, but because it's well-researched!