addressing final nits

docs/intro/arch_overview/http_routing.rst

@@ -23,8 +23,8 @@ request. The router filter supports the following features:
 * :ref:`Path <config_http_conn_man_route_table_route_path_redirect>`/:ref:`host
   <config_http_conn_man_route_table_route_host_redirect>` redirection at the route level.
 * :ref:`Explicit host rewriting <config_http_conn_man_route_table_route_host_rewrite>`.
-* :ref:`Automatic host rewriting <config_http_conn_man_route_table_route_auto_host_rewrite>` based on DNS name of
-  the selected upstream host.
+* :ref:`Automatic host rewriting <config_http_conn_man_route_table_route_auto_host_rewrite>` based on
+  the DNS name of the selected upstream host.
 * :ref:`Prefix rewriting <config_http_conn_man_route_table_route_prefix_rewrite>`.
 * :ref:`Request retries <arch_overview_http_routing_retry>` specified either via HTTP header or via
   route configuration.

test/common/router/router_test.cc

@@ -964,6 +964,8 @@ TEST_F(RouterTest, AutoHostRewriteEnabled) {
   HttpTestUtility::addDefaultHeaders(outgoing_headers);
   outgoing_headers.Host()->value(dns_host);
 
+  ON_CALL(*cm_.conn_pool_.host_, hostname()).WillByDefault(ReturnRef(dns_host));
+
   EXPECT_CALL(callbacks_.route_->route_entry_, timeout())
       .WillOnce(Return(std::chrono::milliseconds(0)));
 
@@ -974,6 +976,8 @@ TEST_F(RouterTest, AutoHostRewriteEnabled) {
                              return nullptr;
                            }));
 
+  // :authority header in the outgoing request should match the DNS name of
+  // the selected upstream host
   EXPECT_CALL(encoder, encodeHeaders(HeaderMapEqualRef(&outgoing_headers), true))
       .WillOnce(Invoke([&](const Http::HeaderMap&, bool) -> void {
         encoder.stream_.resetStream(Http::StreamResetReason::RemoteReset);
@@ -983,18 +987,20 @@ TEST_F(RouterTest, AutoHostRewriteEnabled) {
       .WillOnce(Invoke([&](const Upstream::HostDescriptionPtr host)
                            -> void { EXPECT_EQ(host_address_, host->address()); }));
   EXPECT_CALL(callbacks_.route_->route_entry_, autoHostRewrite()).WillOnce(Return(true));
-  EXPECT_CALL(*cm_.conn_pool_.host_, hostname()).WillRepeatedly(ReturnRef(dns_host));
   router_.decodeHeaders(incoming_headers, true);
 }
 
 TEST_F(RouterTest, AutoHostRewriteDisabled) {
   NiceMock<Http::MockStreamEncoder> encoder;
+  std::string dns_host{"scooby.doo"};
   std::string req_host{"foo.bar.com"};
 
   Http::TestHeaderMapImpl incoming_headers;
   HttpTestUtility::addDefaultHeaders(incoming_headers);
   incoming_headers.Host()->value(req_host);
 
+  ON_CALL(*cm_.conn_pool_.host_, hostname()).WillByDefault(ReturnRef(dns_host));
+
   EXPECT_CALL(callbacks_.route_->route_entry_, timeout())
       .WillOnce(Return(std::chrono::milliseconds(0)));
 
@@ -1005,6 +1011,8 @@ TEST_F(RouterTest, AutoHostRewriteDisabled) {
                              return nullptr;
                            }));
 
+  // :authority header in the outgoing request should match the :authority header of
+  // the incoming request
   EXPECT_CALL(encoder, encodeHeaders(HeaderMapEqualRef(&incoming_headers), true))
       .WillOnce(Invoke([&](const Http::HeaderMap&, bool) -> void {
         encoder.stream_.resetStream(Http::StreamResetReason::RemoteReset);

test/mocks/upstream/host.h

@@ -61,6 +61,7 @@ class MockHostDescription : public HostDescription {
   MOCK_CONST_METHOD0(stats, HostStats&());
   MOCK_CONST_METHOD0(zone, const std::string&());
 
+  std::string hostname_{};
   Network::Address::InstancePtr address_;
   testing::NiceMock<Outlier::MockDetectorHostSink> outlier_detector_;
   testing::NiceMock<MockClusterInfo> cluster_;