feat: extract URL from X-Original-Path/Query headers

rpcserver/jsonrpc_server.go

@@ -277,8 +277,32 @@ func (h *JSONRPCHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 		ctx = context.WithValue(ctx, signerKey{}, signer)
 	}
-	// r.URL
-	ctx = context.WithValue(ctx, urlKey{}, r.URL)
+	// Extract URL from headers (Stage 2) or use r.URL directly (Stage 1)
+	// Proxyd may send X-Original-Path and X-Original-Query independently
+	reqURL := r.URL
+	originalPath := r.Header.Get("X-Original-Path")
+	originalQuery := r.Header.Get("X-Original-Query")
+
+	// Only create new URL if at least one header is present
+	if originalPath != "" || originalQuery != "" {
+		// Start with actual URL values
+		path := r.URL.Path
+		query := r.URL.RawQuery
+
+		// Replace with header values if present
+		if originalPath != "" {
+			path = originalPath
+		}
+		if originalQuery != "" {
+			query = originalQuery
+		}
+
+		reqURL = &url.URL{
+			Path:     path,
+			RawQuery: query,
+		}
+	}
+	ctx = context.WithValue(ctx, urlKey{}, reqURL)
 
 	// read request
 	var req jsonRPCRequest

rpcserver/jsonrpc_server_test.go

@@ -208,3 +208,77 @@ func TestJSONRPCServerReadyzError(t *testing.T) {
 	fmt.Println(rr.Body.String())
 	require.Equal(t, "not ready\n", rr.Body.String())
 }
+
+func TestURLExtraction(t *testing.T) {
+	// Handler that captures URL from context
+	var capturedURL string
+	handlerMethod := func(ctx context.Context) (string, error) {
+		url := GetURL(ctx)
+		capturedURL = url.Path + "?" + url.RawQuery
+		return capturedURL, nil
+	}
+
+	handler, err := NewJSONRPCHandler(map[string]interface{}{
+		"test": handlerMethod,
+	}, JSONRPCHandlerOpts{})
+	require.NoError(t, err)
+
+	t.Run("No headers: uses r.URL (backward compat)", func(t *testing.T) {
+		body := bytes.NewReader([]byte(`{"jsonrpc":"2.0","id":1,"method":"test","params":[]}`))
+		request, err := http.NewRequest(http.MethodPost, "/fast?hint=calldata", body)
+		require.NoError(t, err)
+		request.Header.Add("Content-Type", "application/json")
+
+		rr := httptest.NewRecorder()
+		handler.ServeHTTP(rr, request)
+
+		require.Equal(t, http.StatusOK, rr.Code)
+		require.Equal(t, "/fast?hint=calldata", capturedURL)
+	})
+
+	t.Run("Both headers: reconstructs URL (works with any path)", func(t *testing.T) {
+		// Test with /whatever instead of /fast to prove it's not hardcoded
+		body := bytes.NewReader([]byte(`{"jsonrpc":"2.0","id":1,"method":"test","params":[]}`))
+		request, err := http.NewRequest(http.MethodPost, "/", body)
+		require.NoError(t, err)
+		request.Header.Add("Content-Type", "application/json")
+		request.Header.Add("X-Original-Path", "/whatever")
+		request.Header.Add("X-Original-Query", "hint=hash&builder=flashbots")
+
+		rr := httptest.NewRecorder()
+		handler.ServeHTTP(rr, request)
+
+		require.Equal(t, http.StatusOK, rr.Code)
+		require.Equal(t, "/whatever?hint=hash&builder=flashbots", capturedURL)
+	})
+
+	t.Run("Only query header: uses r.URL.Path", func(t *testing.T) {
+		// Proxyd doesn't send X-Original-Path when path is "/"
+		body := bytes.NewReader([]byte(`{"jsonrpc":"2.0","id":1,"method":"test","params":[]}`))
+		request, err := http.NewRequest(http.MethodPost, "/", body)
+		require.NoError(t, err)
+		request.Header.Add("Content-Type", "application/json")
+		request.Header.Add("X-Original-Query", "hint=hash")
+
+		rr := httptest.NewRecorder()
+		handler.ServeHTTP(rr, request)
+
+		require.Equal(t, http.StatusOK, rr.Code)
+		require.Equal(t, "/?hint=hash", capturedURL)
+	})
+
+	t.Run("Only path header: uses r.URL.RawQuery", func(t *testing.T) {
+		// Proxyd doesn't send X-Original-Query when there's no query string
+		body := bytes.NewReader([]byte(`{"jsonrpc":"2.0","id":1,"method":"test","params":[]}`))
+		request, err := http.NewRequest(http.MethodPost, "/api", body)
+		require.NoError(t, err)
+		request.Header.Add("Content-Type", "application/json")
+		request.Header.Add("X-Original-Path", "/fast")
+
+		rr := httptest.NewRecorder()
+		handler.ServeHTTP(rr, request)
+
+		require.Equal(t, http.StatusOK, rr.Code)
+		require.Equal(t, "/fast?", capturedURL)
+	})
+}