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proxy.go
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/
proxy.go
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.19
// HTTP proxy code
package main
import (
"context"
"io"
"net"
"net/http"
"net/http/httputil"
"strings"
)
// httpProxyHandler returns an HTTP proxy http.Handler using the
// provided backend dialer.
func httpProxyHandler(dialer func(ctx context.Context, netw, addr string) (net.Conn, error)) http.Handler {
rp := &httputil.ReverseProxy{
Director: func(r *http.Request) {}, // no change
Transport: &http.Transport{
DialContext: dialer,
},
}
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.Method != "CONNECT" {
backURL := r.RequestURI
if strings.HasPrefix(backURL, "/") || backURL == "*" {
http.Error(w, "bogus RequestURI; must be absolute URL or CONNECT", 400)
return
}
rp.ServeHTTP(w, r)
return
}
// CONNECT support:
dst := r.RequestURI
c, err := dialer(r.Context(), "tcp", dst)
if err != nil {
w.Header().Set("Tailscale-Connect-Error", err.Error())
http.Error(w, err.Error(), 500)
return
}
defer c.Close()
cc, ccbuf, err := w.(http.Hijacker).Hijack()
if err != nil {
http.Error(w, err.Error(), 500)
return
}
defer cc.Close()
io.WriteString(cc, "HTTP/1.1 200 OK\r\n\r\n")
var clientSrc io.Reader = ccbuf
if ccbuf.Reader.Buffered() == 0 {
// In the common case (with no
// buffered data), read directly from
// the underlying client connection to
// save some memory, letting the
// bufio.Reader/Writer get GC'ed.
clientSrc = cc
}
errc := make(chan error, 1)
go func() {
_, err := io.Copy(cc, c)
errc <- err
}()
go func() {
_, err := io.Copy(c, clientSrc)
errc <- err
}()
<-errc
})
}