Re: [PATCH net-next v3 1/2] ipv6: report why a route was deleted in RTM_DELROUTE

[Yuyang Huang]

On Tue, Jul 28, 2026 at 7:13 PM Ido Schimmel <idosch@xxxxxxxxxx> wrote:

> There are too many changes in this patch. The meaningful changes are
> mixed in with a lot of churn. I suggest splitting it as follows:
>
> 1. Add the rta_del_reason enum and ip6_del_rt_reason(). Call it from
> ip6_del_rt() with RTA_DEL_REASON_UNSPEC. No functional changes.
>
> 2. Propagate the deletion reason argument from ip6_del_rt_reason() all
> the way to fib6_del_route(). Purely a mechanical change with a lot of
> churn.
>
> 3. Change the relevant callers to specify the deletion reason instead of
> RTA_DEL_REASON_UNSPEC. This is the meaningful change.
>
> Now the only thing that is left is to expose the deletion reason to user
> space.
>
> 4. Add a deletion reason argument to rt6_fill_node() and pass UNSPEC.
> Purely a mechanical change with a lot of churn.
>
> 5. Change rt6_fill_node() (and rt6_nlmsg_size()) to expose the reason to
> user space assuming it is not UNSPEC. At this point it is still not
> visible to user space since all the callers pass UNSPEC.
>
> 6. Add inet6_rt_del_notify() (see more below) and call it from
> fib6_del_route() with the deletion reason. The inet6_rt_notify() callers
> do not need to change.
>
> 7. Add the multicast groups and the notifications to rt-route.yaml (see
> more below).
>
> 8. Add the deletion reason to rt-route.yaml.
>
> 9. Add the selftest.

> At least sport and dport are only used in RTM_GETROUTE, but it does seem
> like they won't be rejected if encoded in an RTM_NEWROUTE request, so I
> guess it's OK to put them here.

> This hunk (adding the mcast groups and notifications) is not related to
> the deletion reason. Please split it to a separate patch. There are too
> many changes in this patch as-is.

> Why not use enum rta_del_reason like we do with kfree_skb_reason()?
>
> Also, only one caller calls it from the deletion path, the rest pass
> RTM_NEWROUTE and it's weird to see something like:
>
> inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags, RTA_DEL_REASON_UNSPEC);
>
> Maybe create inet6_rt_del_notify(rt, info, del_reason) and have it call
> __inet6_rt_notify()? Then we don't need any changes in the addition
> path.

> Please use the enum throughout the patch instead of a plain u32.

Thank you very much for all the detailed reviews!

Will adjust all the items properly in patchset v4.

Yuyang