networking: add prefix_rewrite to HTTPRedirect

networking/v1alpha3/virtual_service.proto

@@ -1074,10 +1074,35 @@ message TLSMatchAttributes {
 //   ...
 // ```
 //
+// The following rule redirects requests with a path prefix of /foo to the
+// authority foo.example.com, stripping the /foo prefix from the path:
+//
+// ```yaml
+// apiVersion: networking.istio.io/v1
+// kind: VirtualService
+// metadata:
+//   name: foo-redirect
+// spec:
+//   hosts:
+//   - example.com
+//   http:
+//   - match:
+//     - uri:
+//         prefix: /foo/
+//     redirect:
+//       authority: foo.example.com
+//       prefix_rewrite: /
+// ```
+//
+// With this rule, a request to example.com/foo/bar is redirected to
+// foo.example.com/bar.
+//
 message HTTPRedirect {
   // On a redirect, overwrite the Path portion of the URL with this
   // value. Note that the entire path will be replaced, irrespective of the
   // request URI being matched as an exact path or prefix.
+  //
+  // Mutually exclusive with prefix_rewrite.
   string uri = 1;
 
   // On a redirect, overwrite the Authority/Host portion of the URL with
@@ -1106,6 +1131,17 @@ message HTTPRedirect {
   // On a redirect, Specifies the HTTP status code to use in the redirect
   // response. The default response code is MOVED_PERMANENTLY (301).
   uint32 redirect_code = 3;
+
+  // On a redirect, replace the matched prefix with this value. The route match
+  // must use a prefix match type. The matched prefix is stripped from the path
+  // and this value is prepended.
+  //
+  // Examples (route prefix match: /foo):
+  // - prefix_rewrite: /bar → /foo/baz becomes /bar/baz
+  // - prefix_rewrite: /   → /foo/baz becomes //baz (use /foo/ match to get /baz)
+  //
+  // Mutually exclusive with uri.
+  string prefix_rewrite = 7;
 }
 
 // HTTPDirectResponse can be used to send a fixed response to clients.

releasenotes/notes/redirect-prefix-rewrite.yaml

@@ -0,0 +1,13 @@
+apiVersion: release-notes/v2
+kind: feature
+area: traffic-management
+issue:
+  - 47500
+  - 47777
+  - 52521
+
+releaseNotes:
+  - |
+    **Added** `prefix_rewrite` field to `HTTPRedirect`, allowing redirects that preserve the path
+    suffix. The matched route prefix is stripped and replaced with the specified value (e.g.
+    `example.com/foo/bar` → `foo.example.com/bar`). Mutually exclusive with the existing `uri` field.