From 0ffcb47f0ece2bf5355dd76c0362447eb528d32f Mon Sep 17 00:00:00 2001
From: Rohit Agrawal <rohit.agrawal@databricks.com>
Date: Sun, 5 Jan 2025 19:42:51 +0100
Subject: [PATCH] lua: add new function to get the name of the matched route

Signed-off-by: Rohit Agrawal <rohit.agrawal@databricks.com>
---
 changelogs/current.yaml                       |  4 ++
 .../http/http_filters/lua_filter.rst          | 20 +++++++++
 .../extensions/filters/http/lua/wrappers.cc   |  6 +++
 source/extensions/filters/http/lua/wrappers.h |  9 +++-
 .../filters/http/lua/wrappers_test.cc         | 44 +++++++++++++++++++
 5 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/changelogs/current.yaml b/changelogs/current.yaml
index 909c0053f23d..cd14d76862cd 100644
--- a/changelogs/current.yaml
+++ b/changelogs/current.yaml
@@ -407,6 +407,10 @@ new_features:
   change: |
     Add the option to reduce the rate limit budget based on request/response contexts on stream done.
     See :ref:`apply_on_stream_done <envoy_v3_api_field_config.route.v3.RateLimit.apply_on_stream_done>` for more details.
+- area: lua
+  change: |
+    Added :ref:`routeName() <config_http_filters_lua_stream_info_route_name>` API to the Stream Info Object to get the
+    name of the route matched by the filter chain.
 
 deprecated:
 - area: rbac
diff --git a/docs/root/configuration/http/http_filters/lua_filter.rst b/docs/root/configuration/http/http_filters/lua_filter.rst
index 02483d8dae9f..5eee43fb9d22 100644
--- a/docs/root/configuration/http/http_filters/lua_filter.rst
+++ b/docs/root/configuration/http/http_filters/lua_filter.rst
@@ -823,6 +823,26 @@ Stream info object API
 Returns the string representation of :repo:`HTTP protocol <envoy/http/protocol.h>`
 used by the current request. The possible values are: ``HTTP/1.0``, ``HTTP/1.1``, ``HTTP/2`` and ``HTTP/3*``.
 
+.. _config_http_filters_lua_stream_info_route_name:
+
+``routeName()``
+^^^^^^^^^^^^^^^
+
+.. code-block:: lua
+
+  streamInfo:routeName()
+
+Returns the name of the route matched by the filter chain. Returns an empty string if no route was matched.
+
+Example usage:
+
+.. code-block:: lua
+
+  function envoy_on_request(request_handle)
+    local route_name = request_handle:streamInfo():routeName()
+    request_handle:logInfo("Matched route: " .. route_name)
+  end
+
 .. _config_http_filters_lua_stream_info_downstream_direct_local_address:
 
 ``downstreamDirectLocalAddress()``
diff --git a/source/extensions/filters/http/lua/wrappers.cc b/source/extensions/filters/http/lua/wrappers.cc
index dc3cd331ec1d..1463636ac609 100644
--- a/source/extensions/filters/http/lua/wrappers.cc
+++ b/source/extensions/filters/http/lua/wrappers.cc
@@ -230,6 +230,12 @@ int StreamInfoWrapper::luaRequestedServerName(lua_State* state) {
   return 1;
 }
 
+int StreamInfoWrapper::luaRouteName(lua_State* state) {
+  const std::string& route_name = stream_info_.getRouteName();
+  lua_pushlstring(state, route_name.data(), route_name.length());
+  return 1;
+}
+
 DynamicMetadataMapIterator::DynamicMetadataMapIterator(DynamicMetadataMapWrapper& parent)
     : parent_{parent}, current_{parent_.streamInfo().dynamicMetadata().filter_metadata().begin()} {}
 
diff --git a/source/extensions/filters/http/lua/wrappers.h b/source/extensions/filters/http/lua/wrappers.h
index 0e2ca9abbadb..868230c9eeab 100644
--- a/source/extensions/filters/http/lua/wrappers.h
+++ b/source/extensions/filters/http/lua/wrappers.h
@@ -274,7 +274,8 @@ class StreamInfoWrapper : public Filters::Common::Lua::BaseLuaObject<StreamInfoW
             {"downstreamDirectRemoteAddress", static_luaDownstreamDirectRemoteAddress},
             {"downstreamRemoteAddress", static_luaDownstreamRemoteAddress},
             {"downstreamSslConnection", static_luaDownstreamSslConnection},
-            {"requestedServerName", static_luaRequestedServerName}};
+            {"requestedServerName", static_luaRequestedServerName},
+            {"routeName", static_luaRouteName}};
   }
 
 private:
@@ -328,6 +329,12 @@ class StreamInfoWrapper : public Filters::Common::Lua::BaseLuaObject<StreamInfoW
    */
   DECLARE_LUA_FUNCTION(StreamInfoWrapper, luaRequestedServerName);
 
+  /**
+   * Get the name of the route matched by the filter chain
+   * @return matched route name or an empty string if no route was matched
+   */
+  DECLARE_LUA_FUNCTION(StreamInfoWrapper, luaRouteName);
+
   // Envoy::Lua::BaseLuaObject
   void onMarkDead() override {
     dynamic_metadata_wrapper_.reset();
diff --git a/test/extensions/filters/http/lua/wrappers_test.cc b/test/extensions/filters/http/lua/wrappers_test.cc
index b77a5412bc26..7b7bd658472e 100644
--- a/test/extensions/filters/http/lua/wrappers_test.cc
+++ b/test/extensions/filters/http/lua/wrappers_test.cc
@@ -652,6 +652,50 @@ TEST_F(LuaStreamInfoWrapperTest, DontFinishIterationForDynamicMetadata) {
       "[string \"...\"]:6: cannot create a second iterator before completing the first");
 }
 
+// Test for getting the route name
+TEST_F(LuaStreamInfoWrapperTest, GetRouteName) {
+  const std::string SCRIPT{R"EOF(
+    function callMe(object)
+      testPrint(object:routeName())
+    end
+  )EOF"};
+
+  InSequence s;
+  setup(SCRIPT);
+
+  NiceMock<Envoy::StreamInfo::MockStreamInfo> stream_info;
+  std::string route_name = "test_route";
+  ON_CALL(stream_info, getRouteName()).WillByDefault(testing::ReturnRef(route_name));
+
+  Filters::Common::Lua::LuaDeathRef<StreamInfoWrapper> wrapper(
+      StreamInfoWrapper::create(coroutine_->luaState(), stream_info), true);
+  EXPECT_CALL(printer_, testPrint("test_route"));
+  start("callMe");
+  wrapper.reset();
+}
+
+// Test for empty route name
+TEST_F(LuaStreamInfoWrapperTest, GetEmptyRouteName) {
+  const std::string SCRIPT{R"EOF(
+    function callMe(object)
+      testPrint(object:routeName())
+    end
+  )EOF"};
+
+  InSequence s;
+  setup(SCRIPT);
+
+  NiceMock<Envoy::StreamInfo::MockStreamInfo> stream_info;
+  std::string empty_route;
+  ON_CALL(stream_info, getRouteName()).WillByDefault(testing::ReturnRef(empty_route));
+
+  Filters::Common::Lua::LuaDeathRef<StreamInfoWrapper> wrapper(
+      StreamInfoWrapper::create(coroutine_->luaState(), stream_info), true);
+  EXPECT_CALL(printer_, testPrint(""));
+  start("callMe");
+  wrapper.reset();
+}
+
 } // namespace
 } // namespace Lua
 } // namespace HttpFilters