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|
package handlers
import (
"io"
"net"
"net/http"
"net/http/httputil"
"net/url"
"strings"
)
// NewServiceProxy returns an http.Handler that reverse-proxies requests to
// targetURL, stripping pathPrefix from the request path before forwarding.
// WebSocket upgrade requests are handled via raw TCP hijacking to support
// long-lived connections.
func NewServiceProxy(targetURL, allowedOrigin, pathPrefix string) http.Handler {
target, err := url.Parse(targetURL)
if err != nil {
panic("service proxy: invalid target URL: " + err.Error())
}
stripPrefix := func(p string) string {
s := strings.TrimPrefix(p, pathPrefix)
if s == "" {
s = "/"
}
return s
}
rp := &httputil.ReverseProxy{
Director: func(req *http.Request) {
req.URL.Scheme = target.Scheme
req.URL.Host = target.Host
req.URL.Path = stripPrefix(req.URL.Path)
if req.URL.RawPath != "" {
req.URL.RawPath = stripPrefix(req.URL.RawPath)
}
},
ModifyResponse: func(resp *http.Response) error {
if swa := resp.Header.Get("Service-Worker-Allowed"); swa != "" {
resp.Header.Set("Service-Worker-Allowed", swa)
}
return nil
},
}
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if strings.EqualFold(r.Header.Get("Upgrade"), "websocket") {
if allowedOrigin != "" && r.Header.Get("Origin") != allowedOrigin {
http.Error(w, "forbidden", http.StatusForbidden)
return
}
proxyWebSocket(w, r, target, pathPrefix)
return
}
rp.ServeHTTP(w, r)
})
}
// proxyWebSocket handles WebSocket upgrade via raw TCP hijacking.
func proxyWebSocket(w http.ResponseWriter, r *http.Request, target *url.URL, pathPrefix string) {
host := target.Host
if target.Port() == "" {
switch target.Scheme {
case "https":
host += ":443"
default:
host += ":80"
}
}
upstream, err := net.Dial("tcp", host)
if err != nil {
http.Error(w, "bad gateway", http.StatusBadGateway)
return
}
defer upstream.Close()
r.URL.Scheme = target.Scheme
r.URL.Host = target.Host
stripped := strings.TrimPrefix(r.URL.Path, pathPrefix)
if stripped == "" {
stripped = "/"
}
r.URL.Path = stripped
if r.URL.RawPath != "" {
rawStripped := strings.TrimPrefix(r.URL.RawPath, pathPrefix)
if rawStripped == "" {
rawStripped = "/"
}
r.URL.RawPath = rawStripped
}
r.RequestURI = r.URL.RequestURI()
if err := r.Write(upstream); err != nil {
http.Error(w, "bad gateway", http.StatusBadGateway)
return
}
hijacker, ok := w.(http.Hijacker)
if !ok {
http.Error(w, "websocket not supported", http.StatusInternalServerError)
return
}
clientConn, _, err := hijacker.Hijack()
if err != nil {
return
}
defer clientConn.Close()
done := make(chan struct{}, 2)
go func() {
_, _ = io.Copy(upstream, clientConn)
done <- struct{}{}
}()
go func() {
_, _ = io.Copy(clientConn, upstream)
done <- struct{}{}
}()
<-done
}
|
