Add gateway_selector field to VirtualService for label-based gateway selection

[prashanthjos]

Add Label Selector Support for VirtualService Gateway Selection

Overview

This PR introduces a new gateway_selector field to the VirtualService API that enables selecting gateways using Kubernetes-style label selectors instead of explicit gateway names.

Problem

Currently, VirtualServices require explicitly listing gateway names, which creates operational challenges when updating or replacing gateways across hundreds of VirtualServices.

Related Issue

Fixes: #58426

Solution

Add a new gateway_selector field with Kubernetes-style label selectors.

API Changes

New Message

message GatewayReference {
  string name = 1;
  map<string, string> selector = 2;
}

Updated VirtualService

message VirtualService {
  repeated string hosts = 1;
  repeated string gateways = 2;
  repeated GatewayReference gateway_selector = 7;  // NEW
  repeated HTTPRoute http = 3;
  // ...
}

Examples

Select by labels

gateway_selector:
- selector:
    env: prod
    version: v1

Mix names and selectors

gateway_selector:
- name: "mesh"
- selector:
    env: prod

Benefits

• Update gateways without modifying VirtualServices
• Enable blue-green deployments via relabeling
• Support multi-environment routing
• Reduce configuration drift

Backward Compatibility

• Existing gateways field unchanged
• No breaking changes
• gateway_selector takes precedence if both specified

Files Changed

• networking/v1alpha3/virtual_service.proto
• Generated Go code and CRDs

Related Work

Requires implementation PR in istio/istio repository.

[istio-testing]

Hi @prashanthjos. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[istio-policy-bot]

🤔 🐛 You appear to be fixing a bug in Go code, yet your PR doesn't include updates to any test files. Did you forget to add a test?

Courtesy of your friendly test nag.

[prashanthjos]

@keithmattix, could you please let me know if there’s a specific reason the PR is labeled as do-not-merge/hold?