On Thu, Nov 20, 2025 at 01:18:06PM +0100, Michael Saxl via Bird-users wrote:
Hello,
I'm doing some experiments using radv and bird3. as expected it bird3 automatically sends prefix informations if not somehow disabled.
when I dynamically add a prefix to an interface (ip a a address/64 dev eno1) it immediatly blasts out that prefix with the default parameters (hardcoded in radv.c as radv_prefix_config default_prefix).
Now if that prefix is removed, this prefix is sent as valid_lifetime and preferred_lifetime = 0, but at least linux (NetworkManager) seems to ignore this deprecation, mainly because onlink and autonomous are not set.
Hello Yes, this seems to be a bug. RFC 4861 section 6.3.4 says: Prefix Information options that have the "on-link" (L) flag set indicate a prefix identifying a range of addresses that should be considered on-link. Note, however, that a Prefix Information option with the on-link flag set to zero conveys no information concerning on-link determination and MUST NOT be interpreted to mean that addresses covered by the prefix are off-link. The only way to cancel a previous on-link indication is to advertise that prefix with the L-bit set and the Lifetime set to zero. While RFC 4862 section 4 says: One Prefix Information option field, the "autonomous address-configuration flag", indicates whether or not the option even applies to stateless autoconfiguration. and section 5.5.3 says: a) If the Autonomous flag is not set, silently ignore the Prefix Information option. That seems like a solid case that prefix withdraw should use the same combination of flags like previous announcement. Will check it. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org) "To err is human -- to blame it on a computer is even more so."