Add custom header support for HTTP proxy

[PMExtra]

Background

I'm using Xray as a general network tool without pass GFW purpose.

In my case, I made all network traffic from the private subnet be forwarded to Xray with TPROXY.

Then Xray will do some sniffing to override the destination, then forward the request to a Squid service by HTTP Proxy protocol.

Then I need to take access controlling and auditing with Squid.

So I have to know what's the original source IP address.

Fortunately, Squid support solve source address from X-Forwarded-For header which send with CONNECT proxy request.

Changes

So I made this change to support append custom headers with HTTP PROXY:

I added a new optional setting headers in OutboundConfigurationObject of HTTP outbound.

It support text/template format.

For now, there are 2 properties can be accessed: Source net.Destination and target net.Destination.

There is an configuration example:

{
  "outbounds": [
    {
      "protocol": "http",
      "settings": {
        "servers": [
          {
            "address": "proxy.my.domain",
            "port": 8080
          },
          "headers": {
            "X-Forwarded-For": "{{.Source.Address}}",
            "X-Forwarded-Host": "my.domain",
            "X-Real-IP": "{{if .Source.Address.Family.IsIP}}{{.Source.Address}}{{end}}",
            "Forwarded": "by=4.3.2.1;for={{if .Source.Address.Family.IsIPv4}}{{.Source.Address}}{{else if .Source.Address.Family.IsIPv6}}\"{{.Source.Address}}\"{{end}};host=my.domain;proto=http"
          }
        ]
      }
    }
  ]
}

According to https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded , ipv6 should be quoted and enclosed in square brackets but ipv4 not.

Postscript

I'm sorry for that I'm a beginner of GoLang. Please let me know if there is any bad practice, thanks for your patiences.

I'm still learning to write unit tests with GoLang. So there is no unit test for now, but I've already checked that it works fine in my production workflow.

[yuhan6665]

Thanks for you work! Left a few comments.
I'm beginner in Golang as well. We can learn from each other :)

[yuhan6665]

Maybe, we can use
repeated xray.transport.internet.headers.http.Header header

[PMExtra]

xray.transport.internet.headers.http.Header is designed to pick a random value for a key.
I referenced from xray.transport.internet.websocket.Config to make the current solution.

[yuhan6665]

headers

[PMExtra]

According to xray.transport.internet.websocket.Config and xray.transport.internet.http.Config, the Header property is always in singular form. But in xray.infra.conf.* they are plural form. So I think it should be plural only in config file but singular in other codes.

[yuhan6665]

It seems not used in your examples. Is target needed? I feel the receiving end would have it anyway

[PMExtra]

Yes, it's not needed in my case. I just want to make it more extendable for other usages.

[yuhan6665]

感谢 pr！