fix: Problems with ignored headers removed

Author: codefionn

msgtausch-srv/proxy/http_interceptor.go

@@ -1004,14 +1004,12 @@ func removeHopByHopHeaders(header http.Header) {
 	// Check if this is a WebSocket upgrade request
 	isWebSocketUpgrade := strings.ToLower(header.Get("Upgrade")) == "websocket"
 
-	// List of hop-by-hop headers from RFC 2616
+	// According to RFC 7230, only proxy-specific headers should be removed
+	// We preserve Transfer-Encoding, TE, Trailer, and Keep-Alive for proper HTTP semantics
 	hopByHopHeaders := []string{
-		"Keep-Alive",
 		"Proxy-Authenticate",
 		"Proxy-Authorization",
-		"TE",
-		"Trailers",
-		"Transfer-Encoding",
+		// Note: Keep-Alive, TE, Trailers, and Transfer-Encoding are preserved
 	}
 
 	// For WebSocket upgrades, preserve Connection and Upgrade headers

msgtausch-srv/proxy/proxy.go

@@ -971,14 +971,14 @@ func (p *Server) forwardRequest(w http.ResponseWriter, r *http.Request, client *
 		logger.DebugCtx(ctx, "Detected proxied WebSocket request to %s", targetURL)
 	}
 
+	// According to RFC 7230, proxy-specific headers should be removed,
+	// but we preserve Transfer-Encoding, TE, Trailer, and Keep-Alive for proper HTTP semantics
 	skip := map[string]struct{}{
 		"Proxy-Connection":    {},
-		"Keep-Alive":          {},
 		"Proxy-Authenticate":  {},
 		"Proxy-Authorization": {},
-		"Te":                  {},
-		"Trailer":             {},
-		"Transfer-Encoding":   {},
+		// Note: Keep-Alive, TE, Trailer, and Transfer-Encoding are preserved
+		// to maintain proper HTTP/1.1 connection and transfer semantics
 	}
 
 	isWebSocketConnection := isWebSocketRequest || isProxiedWebSocket

msgtausch-srv/proxy/proxy_basic_test.go

@@ -409,16 +409,15 @@ func TestHTTP2ViaConnect(t *testing.T) {
 // TestForwardRequestHeaderSkipping verifies that hop-by-hop and proxy-specific headers
 // are correctly skipped when forwarding requests.
 func TestForwardRequestHeaderSkipping(t *testing.T) {
+	// Only proxy-specific headers should be skipped, per RFC 7230
+	// Transfer-Encoding, TE, Trailer, and Keep-Alive are preserved for proper HTTP semantics
 	skippedHeaders := map[string]struct{}{
 		"Proxy-Connection":    {},
 		"Connection":          {},
-		"Keep-Alive":          {},
 		"Proxy-Authenticate":  {},
 		"Proxy-Authorization": {},
-		"Te":                  {},
-		"Trailer":             {},
-		"Transfer-Encoding":   {},
 		"Upgrade":             {},
+		// Note: Keep-Alive, TE, Trailer, and Transfer-Encoding are no longer skipped
 	}
 
 	// Create a test HTTP server that echoes received headers