net/http/httputil: extract duplicate code as removeConnectionHeaders

Change-Id: I50389752dcbf5d058ce11256a414be7955cdb77f
Reviewed-on: https://go-review.googlesource.com/71070
Run-TryBot: Tom Bergan <tombergan@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tom Bergan <tombergan@google.com>

src/net/http/httputil/reverseproxy.go

@@ -169,15 +169,7 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	p.Director(outreq)
 	outreq.Close = false
 
-	// Remove hop-by-hop headers listed in the "Connection" header.
-	// See RFC 2616, section 14.10.
-	if c := outreq.Header.Get("Connection"); c != "" {
-		for _, f := range strings.Split(c, ",") {
-			if f = strings.TrimSpace(f); f != "" {
-				outreq.Header.Del(f)
-			}
-		}
-	}
+	removeConnectionHeaders(outreq.Header)
 
 	// Remove hop-by-hop headers to the backend. Especially
 	// important is "Connection" because we want a persistent
@@ -205,15 +197,7 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	// Remove hop-by-hop headers listed in the
-	// "Connection" header of the response.
-	if c := res.Header.Get("Connection"); c != "" {
-		for _, f := range strings.Split(c, ",") {
-			if f = strings.TrimSpace(f); f != "" {
-				res.Header.Del(f)
-			}
-		}
-	}
+	removeConnectionHeaders(res.Header)
 
 	for _, h := range hopHeaders {
 		res.Header.Del(h)
@@ -265,6 +249,18 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	}
 }
 
+// removeConnectionHeaders removes hop-by-hop headers listed in the "Connection" header of h.
+// See RFC 2616, section 14.10.
+func removeConnectionHeaders(h http.Header) {
+	if c := h.Get("Connection"); c != "" {
+		for _, f := range strings.Split(c, ",") {
+			if f = strings.TrimSpace(f); f != "" {
+				h.Del(f)
+			}
+		}
+	}
+}
+
 func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader) {
 	if p.FlushInterval != 0 {
 		if wf, ok := dst.(writeFlusher); ok {