xdsclient/xdsresource: add AutoHostRewrite and Endpoint Hostname support #8728

Pranjali-2501 · 2025-11-26T16:25:09Z

This PR implements the validation logic and extracting per endpoint Hostname attributes from xDS resources for gRFC A81

Key Changes:

RDS Resource Validation :
- The boolean value of RouteAction.auto_host_rewrite is extracted from the RDS resource and stored in route struct
- This field is only set to true in the parsed route struct if the trusted_xds_server option is present in the ServerConfig and the global environment variable for authority overriding is enabled.
EDS Resource Validation:
- The Endpoint.hostname field is extracted from the EDS resource and will be stored as a hostname string in parsed endpoint struct. It will be changed to be an per-endpoint resolver attribute in a follow-up PR.

RELEASE NOTES: None

codecov · 2025-11-26T16:28:25Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.22%. Comparing base (a764d3f) to head (8f184b4).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8728      +/-   ##
==========================================
+ Coverage   83.21%   83.22%   +0.01%     
==========================================
  Files         419      419              
  Lines       32443    32454      +11     
==========================================
+ Hits        26997    27011      +14     
- Misses       4056     4058       +2     
+ Partials     1390     1385       -5

Files with missing lines	Coverage Δ
internal/envconfig/envconfig.go	`100.00% <ø> (ø)`
internal/xds/xdsclient/xdsresource/filter_chain.go	`93.92% <100.00%> (+0.55%)`	⬆️
...ds/xdsclient/xdsresource/listener_resource_type.go	`96.15% <100.00%> (ø)`
...dsclient/xdsresource/route_config_resource_type.go	`93.33% <100.00%> (ø)`
...nternal/xds/xdsclient/xdsresource/unmarshal_eds.go	`94.32% <100.00%> (+0.04%)`	⬆️
...nternal/xds/xdsclient/xdsresource/unmarshal_lds.go	`88.46% <100.00%> (ø)`
...nternal/xds/xdsclient/xdsresource/unmarshal_rds.go	`87.74% <100.00%> (+0.14%)`	⬆️

... and 24 files with indirect coverage changes

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easwars

The PR description says:

This string value is included as a per-endpoint resolver attribute (hostname) in the parsed resource struct.

But the PR only stores it as a string, and not as a resolver attribute. The per-endpoint resolver attribute is defined here:

grpc-go/resolver/resolver.go

Line 191 in 69769dc

Attributes *attributes.Attributes

This means that the parsed Endpoint struct defined here:

grpc-go/internal/xds/xdsclient/xdsresource/type_eds.go

Line 51 in 69769dc

type Endpoint struct {

needs to be changed to contain a resolver.Endpoint instead of a slice of address strings, and the newly added HostName field and some of the other existing things like Weight and HashKey also need to move into the endpoint attributes. This is probably big enough to be made as a separate PR though. Let's discuss this offline.

But for now, maybe the PR description need to be modified though to state that we are only storing it as a string for now and that in a follow-up PR we will change it to be an endpoint attribute.

easwars · 2025-11-26T19:08:32Z

internal/envconfig/envconfig.go

+	// XDSAuthorityRewrite is set if xDS authority rewriting is enabled,
+	// according to gRFC A81. It can be enabled by setting
+	// GRPC_EXPERIMENTAL_XDS_AUTHORITY_REWRITE to true.


Nit: Maybe something like:

// XDSAuthorityRewrite indicates whether xDS authority rewriting is enabled. // This feature is defined in gRFC A81 and is enabled by setting the // environment variable GRPC_EXPERIMENTAL_XDS_AUTHORITY_REWRITE to "true".

easwars · 2025-11-26T19:19:01Z

internal/xds/xdsclient/xdsresource/unmarshal_lds.go

 		update.RouteConfigName = name
 	case *v3httppb.HttpConnectionManager_RouteConfig:
-		routeU, err := generateRDSUpdateFromRouteConfiguration(apiLis.GetRouteConfig())
+		routeU, err := generateRDSUpdateFromRouteConfiguration(nil, apiLis.GetRouteConfig())


Why are we passing nil here? This is an inline route configuration in the listener resource and needs to be handled exactly the same way as the non-inlined version is. So, you would have to plumb the DecodeOptions all the way from listenerResourceDecoder.Decode to unmarshalListenerResource to here (just like you are currently doing for the RDS decoding pipeline).

Made the changes.

easwars · 2025-11-26T19:24:35Z

internal/xds/xdsclient/xdsresource/filter_chain.go

 					// Can specify v3 here, as will never get to this function
 					// if v2.
-					routeU, err := generateRDSUpdateFromRouteConfiguration(hcm.GetRouteConfig())
+					routeU, err := generateRDSUpdateFromRouteConfiguration(nil, hcm.GetRouteConfig())


It is fine to pass nil here since this is server side listener resource processing and here we don't have to worry about authority rewriting. We might have to plump the decode options to this at some point in the future if they are required for something else on the server-side, but for now, we are good.

easwars · 2025-11-26T19:27:31Z

internal/xds/xdsclient/xdsresource/route_config_resource_type.go

-func (d *routeConfigResourceDecoder) Decode(resource *xdsclient.AnyProto, _ xdsclient.DecodeOptions) (*xdsclient.DecodeResult, error) {
-	name, rc, err := unmarshalRouteConfigResource(resource.ToAny())
+func (d *routeConfigResourceDecoder) Decode(resource *xdsclient.AnyProto, opts xdsclient.DecodeOptions) (*xdsclient.DecodeResult, error) {
+	name, rc, err := unmarshalRouteConfigResource(&opts, resource.ToAny())


Nit: Why is the order of arguments being reversed here? It would be nicer if we can retain the same order of arguments for Decode and unmarshalRouteConfigResource and the whole chain down from there. For here, and for the LDS side as well (which you are going to have to add, see another comment for more details).

easwars · 2025-11-26T19:30:28Z

internal/xds/xdsclient/xdsresource/unmarshal_rds_test.go

+			}
+
+			got := update.VirtualHosts[0].Routes[0].AutoHostRewrite
+


Nit: delete newline

easwars · 2025-11-26T19:31:21Z

internal/xds/xdsclient/xdsresource/unmarshal_rds_test.go

+		ldsTarget   = "lds.target.good:1111"
+	)
+
+	buildRouteConfig := func() *v3routepb.RouteConfiguration {


Why is this a function? Can this be declared inside the test body instead?

easwars · 2025-11-26T19:32:03Z

internal/xds/xdsclient/xdsresource/unmarshal_rds_test.go

+					Action: &v3routepb.Route_Route{
+						Route: &v3routepb.RouteAction{
+							ClusterSpecifier:     &v3routepb.RouteAction_Cluster{Cluster: clusterName},
+							HostRewriteSpecifier: &v3routepb.RouteAction_AutoHostRewrite{AutoHostRewrite: &wrapperspb.BoolValue{Value: true}},


We probably also need test cases for when the AutoHostRewrite field in the proto is false.

Added a testcase for that.

easwars · 2025-11-26T19:35:46Z

internal/xds/xdsclient/xdsresource/unmarshal_eds_test.go

 			m: func() *v3endpointpb.ClusterLoadAssignment {
 				clab0 := newClaBuilder("test", nil)
-				clab0.addLocality("locality-1", 1, 1, []endpointOpts{{addrWithPort: "addr1:314"}}, &addLocalityOptions{
+				clab0.addLocality("locality-1", 1, 1, []endpointOpts{{addrWithPort: "addr1:314", hostname: "addr1"}}, &addLocalityOptions{


I know these callsites are existing art, but they are really hard to read. While you are here, could you please follow guidelines from here to make them more readable. See: go/go-style/decisions#func-formatting

Thanks.

Made the changes.

resource validation changes

c3355c8

Pranjali-2501 added this to the 1.78 Release milestone Nov 26, 2025

Pranjali-2501 added Type: Feature New features or improvements in behavior Area: xDS Includes everything xDS related, including LB policies used with xDS. labels Nov 26, 2025

Pranjali-2501 requested a review from easwars November 26, 2025 16:33

Pranjali-2501 assigned easwars Nov 26, 2025

easwars reviewed Nov 26, 2025

View reviewed changes

easwars assigned Pranjali-2501 and unassigned easwars Nov 26, 2025

resolving comments

8f184b4

Pranjali-2501 requested a review from easwars November 29, 2025 21:42

Pranjali-2501 assigned easwars and unassigned Pranjali-2501 Nov 29, 2025

xdsclient/xdsresource: add AutoHostRewrite and Endpoint Hostname support #8728

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xdsclient/xdsresource: add AutoHostRewrite and Endpoint Hostname support #8728

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Pranjali-2501 commented Nov 26, 2025 •

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