golang反向代理无法访问

httputilmain

package main

import (
	"net/http"
	"net/http/httputil"
	"net/url"
)

func main() {
	u, _ := url.Parse("http://localhost:8888")
	http.Handle("/", httputil.NewSingleHostReverseProxy(u))
	http.ListenAndServe(":9999", nil)
}

:9999:8888:8888

404www.baidu.comNewSingleHostReverseProxy

type ReverseProxy struct {
	Director func(*http.Request)
	Transport http.RoundTripper
	FlushInterval time.Duration
	ErrorLog *log.Logger
	BufferPool BufferPool
	ModifyResponse func(*http.Response) error
	ErrorHandler func(http.ResponseWriter, *http.Request, error)
}

并无神奇之处，反向代理就是一个结构体！

ErrorHandler404

ModifyResponse

BufferPool

Errorlog

FlushInterval

Transport

Director

接下来就来看看我们是如何得到一个反向代理结构体的。

func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
	targetQuery := target.RawQuery
	director := func(req *http.Request) {
		req.URL.Scheme = target.Scheme
		req.URL.Host = target.Host
		req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
		if targetQuery == "" || req.URL.RawQuery == "" {
			req.URL.RawQuery = targetQuery + req.URL.RawQuery
		} else {
			req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
		}
		if _, ok := req.Header["User-Agent"]; !ok {
			req.Header.Set("User-Agent", "")
		}
	}
	return &ReverseProxy{Director: director}
}

NewSingleHostReverseProxyDirectorReverseProxydirectorHostPathreq.Host

NewSingleHostReverseProxy

func NewProxy(target *url.URL) *httputil.ReverseProxy {
	targetQuery := target.RawQuery
	director := func(req *http.Request) {
		req.Host = target.Host // -- 加入这句 --
		req.URL.Scheme = target.Scheme
		req.URL.Host = target.Host
		req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
		if targetQuery == "" || req.URL.RawQuery == "" {
			req.URL.RawQuery = targetQuery + req.URL.RawQuery
		} else {
			req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
		}
		if _, ok := req.Header["User-Agent"]; !ok {
			// explicitly disable User-Agent so it's not set to default value
			req.Header.Set("User-Agent", "")
		}
	}
	return &httputil.ReverseProxy{Director: director}
}

httputil.NewSingleHostReverseProxy(u)NewProxy(u)

DirectorNewSingleHostReverseProxyDirector

p := httputil.NewSingleHostReverseProxy(u)
d := p.Director
p.Director = func(r *http.Request) {
	d(r)
	r.Host = u.Host
}

最后附图一张。