Re: [v6ops] IPv6 link-local traffic questions

[Toerless Eckert <[e-mail]>]

On Thu, Mar 12, 2020 at 12:18:32PM +1100, Mark Smith wrote:
> RFC4007  allows packets with link-local destinations to be forwarded
> by a router, but only back onto the same link:

Oh, my favourite coffin nail RFC.

> "Thus, if a
>    router receives a packet with a link-local destination address that
>    is not one of the router's own link-local addresses on the arrival
>    link, the router is expected to try to forward the packet to the
>    destination on that link (subject to successful determination of the
>    destination's link-layer address via the Neighbor Discovery protocol
>    [9]).  The forwarded packet may be transmitted back through the
>    arrival interface, or through any other interface attached to the
>    same link."
>
> 
> I think in theory that could also mean forwarded to another router on
> the link that then forwards back again onto the link etc., so it is
> valid for a packet with a link-local destination address to have an
> initial Hop Count value that allows it to be forwarded by multiple
> routers, all limited to being forwarded within the same link.

So this behavior breaks both TTL=1 and RFC5082 packets.

Nice. This RFC is getting better every time i learn more of it.

> This draft might be useful, as it collects together and summarises
> information about using Link-Local Addresses (and is something I've
> been meaning to get back to updating, suggestions welcome):
> 
> How to use IPv6 Link-Local Addresses in Applications
> https://tools.ietf.org/html/draft-smith-ipv6-link-locals-apps-00

Nice.

Let me split that off.

cheers
    Toerless