adaptor ResponseWriter - adding Hijack method and pass proper fields (#1525)

* adding hijack method and pass proper fields

* adding hijack method and pass proper fields - adding tests

* improve hijack handling, use proper test for hijacking

* extend hijackhandler propogation to NewFastHTTPHandlerFunc

* align hijacking of fasthttp adaptor net request with fasthttp request, safe conn handling for proper release of resources and custom hijack handler for more controlled by hijacking implementation

* Implement actual behaviour of net/http Hijacker

---------

Co-authored-by: Erik Dubbelboer <erik@dubbelboer.com>

fasthttpadaptor/adaptor.go

@@ -3,8 +3,11 @@
 package fasthttpadaptor
 
 import (
+	"bufio"
 	"io"
+	"net"
 	"net/http"
+	"sync"
 
 	"github.com/valyala/fasthttp"
 )
@@ -53,8 +56,10 @@ func NewFastHTTPHandler(h http.Handler) fasthttp.RequestHandler {
 			ctx.Error("Internal Server Error", fasthttp.StatusInternalServerError)
 			return
 		}
-
-		w := netHTTPResponseWriter{w: ctx.Response.BodyWriter()}
+		w := netHTTPResponseWriter{
+			w:   ctx.Response.BodyWriter(),
+			ctx: ctx,
+		}
 		h.ServeHTTP(&w, r.WithContext(ctx))
 
 		ctx.SetStatusCode(w.StatusCode())
@@ -86,6 +91,7 @@ type netHTTPResponseWriter struct {
 	statusCode int
 	h          http.Header
 	w          io.Writer
+	ctx        *fasthttp.RequestCtx
 }
 
 func (w *netHTTPResponseWriter) StatusCode() int {
@@ -111,3 +117,43 @@ func (w *netHTTPResponseWriter) Write(p []byte) (int, error) {
 }
 
 func (w *netHTTPResponseWriter) Flush() {}
+
+type wrappedConn struct {
+	net.Conn
+
+	wg   sync.WaitGroup
+	once sync.Once
+}
+
+func (c *wrappedConn) Close() (err error) {
+	c.once.Do(func() {
+		err = c.Conn.Close()
+		c.wg.Done()
+	})
+	return
+}
+
+func (w *netHTTPResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	// Hijack assumes control of the connection, so we need to prevent fasthttp from closing it or
+	// doing anything else with it.
+	w.ctx.HijackSetNoResponse(true)
+
+	conn := &wrappedConn{Conn: w.ctx.Conn()}
+	conn.wg.Add(1)
+	w.ctx.Hijack(func(net.Conn) {
+		conn.wg.Wait()
+	})
+
+	bufW := bufio.NewWriter(conn)
+
+	// Write any unflushed body to the hijacked connection buffer.
+	unflushedBody := w.ctx.Response.Body()
+	if len(unflushedBody) > 0 {
+		if _, err := bufW.Write(unflushedBody); err != nil {
+			conn.Close()
+			return nil, nil, err
+		}
+	}
+
+	return conn, &bufio.ReadWriter{Reader: bufio.NewReader(conn), Writer: bufW}, nil
+}

fasthttpadaptor/adaptor_test.go

@@ -7,8 +7,10 @@ import (
 	"net/url"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/valyala/fasthttp"
+	"github.com/valyala/fasthttp/fasthttputil"
 )
 
 func TestNewFastHTTPHandler(t *testing.T) {
@@ -143,3 +145,74 @@ func setContextValueMiddleware(next fasthttp.RequestHandler, key string, value a
 		next(ctx)
 	}
 }
+
+func TestHijack(t *testing.T) {
+	t.Parallel()
+
+	nethttpH := func(w http.ResponseWriter, r *http.Request) {
+		if f, ok := w.(http.Hijacker); !ok {
+			t.Errorf("expected http.ResponseWriter to implement http.Hijacker")
+		} else {
+			if _, err := w.Write([]byte("foo")); err != nil {
+				t.Error(err)
+			}
+
+			if c, rw, err := f.Hijack(); err != nil {
+				t.Error(err)
+			} else {
+				if _, err := rw.Write([]byte("bar")); err != nil {
+					t.Error(err)
+				}
+
+				if err := rw.Flush(); err != nil {
+					t.Error(err)
+				}
+
+				if err := c.Close(); err != nil {
+					t.Error(err)
+				}
+			}
+		}
+	}
+
+	s := &fasthttp.Server{
+		Handler: NewFastHTTPHandler(http.HandlerFunc(nethttpH)),
+	}
+
+	ln := fasthttputil.NewInmemoryListener()
+
+	go func() {
+		if err := s.Serve(ln); err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+	}()
+
+	clientCh := make(chan struct{})
+	go func() {
+		c, err := ln.Dial()
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+
+		if _, err = c.Write([]byte("GET / HTTP/1.1\r\nHost: aa\r\n\r\n")); err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+
+		buf, err := io.ReadAll(c)
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+
+		if string(buf) != "foobar" {
+			t.Errorf("unexpected response: %q. Expecting %q", buf, "foobar")
+		}
+
+		close(clientCh)
+	}()
+
+	select {
+	case <-clientCh:
+	case <-time.After(time.Second):
+		t.Fatal("timeout")
+	}
+}