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A simple HTTP proxy by Golang
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package main | |
import ( | |
"flag" | |
"io" | |
"log" | |
"net" | |
"net/http" | |
"strings" | |
) | |
// Hop-by-hop headers. These are removed when sent to the backend. | |
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html | |
var hopHeaders = []string{ | |
"Connection", | |
"Keep-Alive", | |
"Proxy-Authenticate", | |
"Proxy-Authorization", | |
"Te", // canonicalized version of "TE" | |
"Trailers", | |
"Transfer-Encoding", | |
"Upgrade", | |
} | |
func copyHeader(dst, src http.Header) { | |
for k, vv := range src { | |
for _, v := range vv { | |
dst.Add(k, v) | |
} | |
} | |
} | |
func delHopHeaders(header http.Header) { | |
for _, h := range hopHeaders { | |
header.Del(h) | |
} | |
} | |
func appendHostToXForwardHeader(header http.Header, host string) { | |
// If we aren't the first proxy retain prior | |
// X-Forwarded-For information as a comma+space | |
// separated list and fold multiple headers into one. | |
if prior, ok := header["X-Forwarded-For"]; ok { | |
host = strings.Join(prior, ", ") + ", " + host | |
} | |
header.Set("X-Forwarded-For", host) | |
} | |
type proxy struct { | |
} | |
func (p *proxy) ServeHTTP(wr http.ResponseWriter, req *http.Request) { | |
log.Println(req.RemoteAddr, " ", req.Method, " ", req.URL) | |
if req.URL.Scheme != "http" && req.URL.Scheme != "https" { | |
msg := "unsupported protocal scheme "+req.URL.Scheme | |
http.Error(wr, msg, http.StatusBadRequest) | |
log.Println(msg) | |
return | |
} | |
client := &http.Client{} | |
//http: Request.RequestURI can't be set in client requests. | |
//http://golang.org/src/pkg/net/http/client.go | |
req.RequestURI = "" | |
delHopHeaders(req.Header) | |
if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil { | |
appendHostToXForwardHeader(req.Header, clientIP) | |
} | |
resp, err := client.Do(req) | |
if err != nil { | |
http.Error(wr, "Server Error", http.StatusInternalServerError) | |
log.Fatal("ServeHTTP:", err) | |
} | |
defer resp.Body.Close() | |
log.Println(req.RemoteAddr, " ", resp.Status) | |
delHopHeaders(resp.Header) | |
copyHeader(wr.Header(), resp.Header) | |
wr.WriteHeader(resp.StatusCode) | |
io.Copy(wr, resp.Body) | |
} | |
func main() { | |
var addr = flag.String("addr", "127.0.0.1:8080", "The addr of the application.") | |
flag.Parse() | |
handler := &proxy{} | |
log.Println("Starting proxy server on", *addr) | |
if err := http.ListenAndServe(*addr, handler); err != nil { | |
log.Fatal("ListenAndServe:", err) | |
} | |
} |
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