Re: [PATCH v3 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.

On 1/22/21 9:02 PM, Maciej Żenczykowski wrote:

Why can't we get rid of the special case for 0 and simply make 1024 the
default value?

That would work too.

As for making it an RA option: it's not clear how that would work, the
use case I see for this is for example two connections to the internet,
of which one is clearly better (higher throughput, lower latency, lower
packet loss, etc) then the other.

The upstream routers would have to somehow coordinate with each other
the metric values... that seems impossible to achieve in practice -
unless they do something like report expected down/up
bandwidth, latency, etc...  While some sort of policy on the machine
itself seems much more feasible (for example wired interface > wireless
interface > cell interface or something like that)

I was thinking the admin of the network controls the RAs and knows which
paths are preferred over the admin of the node receiving the RA (not
practical for a mobile setup with cell vs wifi, but is for a DC which is
the driving use case).

But it takes an extension to IPv6/ndisc to add metric as an RA option,
so not realistic in a reasonable time frame.