expr: Add upstream.locality attribute to obtain upstream host locality

docs/root/intro/arch_overview/advanced/attributes.rst

@@ -154,6 +154,7 @@ The following attributes are available once the upstream connection is establish
    upstream.transport_failure_reason, string, The upstream transport failure reason e.g. certificate validation failed
    upstream.request_attempt_count, uint, The count of upstream request attempts. A value of ‘0’ indicates that the request was never attempted upstream
    upstream.cx_pool_ready_duration, duration, Total duration from when the upstream request was created to when the upstream connection pool is ready
+   upstream.locality, :ref:`Locality<envoy_v3_api_msg_config.core.v3.locality>`, Locality information of upstream host
 
 Metadata and filter state
 -------------------------

source/extensions/filters/common/expr/context.cc

@@ -359,6 +359,18 @@ const UpstreamLookupValues& UpstreamLookupValues::get() {
              }
              return {};
            }},
+          {UpstreamLocality,
+           [](const UpstreamWrapper& wrapper) -> absl::optional<CelValue> {
+             if (!wrapper.info_.upstreamInfo().has_value()) {
+               return {};
+             }
+             auto upstream_host = wrapper.info_.upstreamInfo().value().get().upstreamHost();
+             if (upstream_host == nullptr) {
+               return {};
+             }
+             return CelProtoWrapper::CreateMessage(&upstream_host.get()->locality(),
+                                                   &wrapper.arena_);
+           }},
           {UpstreamTransportFailureReason,
            [](const UpstreamWrapper& wrapper) -> absl::optional<CelValue> {
              if (!wrapper.info_.upstreamInfo().has_value()) {

source/extensions/filters/common/expr/context.h

@@ -83,6 +83,7 @@ constexpr absl::string_view Destination = "destination";
 // Upstream properties
 constexpr absl::string_view Upstream = "upstream";
 constexpr absl::string_view UpstreamLocalAddress = "local_address";
+constexpr absl::string_view UpstreamLocality = "locality";
 constexpr absl::string_view UpstreamTransportFailureReason = "transport_failure_reason";
 constexpr absl::string_view UpstreamRequestAttemptCount = "request_attempt_count";
 constexpr absl::string_view UpstreamConnectionPoolReadyDuration = "cx_pool_ready_duration";

test/extensions/filters/common/expr/BUILD

@@ -23,6 +23,7 @@ envoy_extension_cc_test(
     tags = ["skip_on_windows"],
     deps = [
         "//source/common/network:filter_state_dst_address_lib",
+        "//source/common/protobuf:utility_lib",
         "//source/common/router:string_accessor_lib",
         "//source/common/stream_info:stream_info_lib",
         "//source/extensions/clusters/original_dst:original_dst_cluster_lib",
@@ -36,6 +37,7 @@ envoy_extension_cc_test(
         "//test/mocks/upstream:host_mocks",
         "//test/test_common:test_runtime_lib",
         "//test/test_common:utility_lib",
+        "@envoy_api//envoy/config/core/v3:pkg_cc_proto",
     ],
 )
 

test/extensions/filters/common/expr/context_test.cc

@@ -1,7 +1,10 @@
+#include "envoy/config/core/v3/base.pb.h"
+
 #include "source/common/network/address_impl.h"
 #include "source/common/network/filter_state_dst_address.h"
 #include "source/common/network/utility.h"
 #include "source/common/protobuf/protobuf.h"
+#include "source/common/protobuf/utility.h"
 #include "source/common/router/string_accessor_impl.h"
 #include "source/common/stream_info/filter_state_impl.h"
 #include "source/extensions/filters/common/expr/cel_state.h"
@@ -548,6 +551,10 @@ TEST(Context, ConnectionAttributes) {
       Network::Utility::parseInternetAddressNoThrow("10.1.2.3", 679, false);
   Network::Address::InstanceConstSharedPtr upstream_local_address =
       Network::Utility::parseInternetAddressNoThrow("10.1.2.3", 1000, false);
+  ::envoy::config::core::v3::Locality upstream_locality;
+  upstream_locality.set_region("upstream_locality_region");
+  upstream_locality.set_zone("upstream_locality_zone");
+  upstream_locality.set_sub_zone("upstream_locality_sub_zone");
   const std::string sni_name = "kittens.com";
   info.downstream_connection_info_provider_->setLocalAddress(local);
   info.downstream_connection_info_provider_->setRemoteAddress(remote);
@@ -570,6 +577,7 @@ TEST(Context, ConnectionAttributes) {
 
   EXPECT_CALL(*downstream_ssl_info, peerCertificatePresented()).WillRepeatedly(Return(true));
   EXPECT_CALL(*upstream_host, address()).WillRepeatedly(Return(upstream_address));
+  EXPECT_CALL(*upstream_host, locality()).WillRepeatedly(ReturnRef(upstream_locality));
 
   const std::string tls_version = "TLSv1";
   EXPECT_CALL(*downstream_ssl_info, tlsVersion()).WillRepeatedly(ReturnRef(tls_version));
@@ -832,6 +840,14 @@ TEST(Context, ConnectionAttributes) {
     ASSERT_TRUE(value.value().IsString());
     EXPECT_EQ(upstream_transport_failure_reason, value.value().StringOrDie().value());
   }
+
+  {
+    auto value = upstream[CelValue::CreateStringView(UpstreamLocality)];
+    ASSERT_TRUE(value.has_value());
+    ASSERT_TRUE(value.value().IsMessage());
+    EXPECT_TRUE(Protobuf::util::MessageDifferencer::Equals(*value.value().MessageOrDie(),
+                                                           upstream_locality));
+  }
 }
 
 TEST(Context, FilterStateAttributes) {
@@ -1187,6 +1203,11 @@ TEST(Context, UpstreamEdgeCases) {
     const auto value = upstream[CelValue::CreateStringView(UpstreamConnectionPoolReadyDuration)];
     EXPECT_FALSE(value.has_value());
   }
+
+  {
+    const auto value = upstream[CelValue::CreateStringView(UpstreamLocality)];
+    EXPECT_FALSE(value.has_value());
+  }
 }
 
 TEST(Context, ExtractSslInfoEmptyValues) {