This patch is a follow up of [1]. "get_subnet" is a read-only operation; it should be possible for network readers to retrieve the subnet too. NOTE: the release note refers to this patch and [1]. Because [1] has been backported up to 2023.2, this patch should be backported too. [1]https://review.opendev.org/q/Iae2e3a31eb65d68dc0d3d0f9dd9fc8cf83260769 Related-Bug: #2038646 Change-Id: I05aeebe1db8ea7cadb292e60b5b322069a557c16