net/http/httputil: permit ReverseProxy to change Host header

[linquize]

net/http/httputil: ReverseProxy
Currently it preserves HTTP request Host header.
However, this may cause problem for some servers complaining Host not match.
I suggest to have a option to change Host header

For example: A reverse proxy
http://a.com/* -> http://192.168.1.123/*
The client sends HTTP request with header Host: a.com
After forwarding, the server expects HTTP request header Host: 192.168.1.123, so we need to change it.

In https://github.com/golang/go/blob/master/src/net/http/httputil/reverseproxy.go

func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
    ......
    req.URL.Host = target.Host
    req.Host = target.Host // Add this line to change Host header
    ......
}

[danp]

Do you have an example that shows the target receives a different Host header? As the docs say, Request.URL.Host is the server to connect to, Request.Host is the value used for the Host header.

[danp]

I believe this is also specifically tested for in this test. Note the checking of req.Host in the backend server to verify it stays the same as what was in the original request sent to the proxy.

[danp]

Sorry, I misread. If you want to modify the Host header in this way you'll probably need to define your own ReverseProxy with a custom Director.

[bradfitz]

Closing due to lack of reply. I think this is probably already sufficiently configurable.