ReferenceGrant

ReferenceGrant identifies kinds of resources in other namespaces that are trusted to reference the specified kinds of resources in the same namespace as the policy. Each ReferenceGrant can be used to represent a unique trust relationship. Additional Reference Grants can be used to add to the set of trusted sources of inbound references for the namespace they are defined within. A ReferenceGrant is required for all cross-namespace references in Gateway API (with the exception of cross-namespace Route-Gateway attachment, which is governed by the AllowedRoutes configuration on the Gateway, and cross-namespace Service ParentRefs on a "consumer" mesh Route, which defines routing rules applicable only to workloads in the Route namespace). ReferenceGrants allowing a reference from a Route to a Service are only applicable to BackendRefs. ReferenceGrant is a form of runtime verification allowing users to assert which cross-namespace object references are permitted. Implementations that support ReferenceGrant MUST NOT permit cross-namespace references which have no grant, and MUST respond to the removal of a grant by revoking the access that the grant allowed.