On 07/15/2018 09:35 AM, dsah...@kernel.org wrote:
> From: David Ahern <dsah...@gmail.com>
>
> Eric reported that reverting the patch that fixed and simplified IPv6
> multipath routes means reverting back to invalid userspace notifications.
> eg.,
> $ ip -6 route add 2001:db8:1::/64 nexthop dev eth0 nexthop dev eth1
>
> only generates a single notification:
> 2001:db8:1::/64 dev eth0 metric 1024 pref medium
>
> While working on a fix for this problem I found another case that is just
> broken completely - a multipath route with a gateway followed by device
> followed by gateway:
> $ ip -6 ro add 2001:db8:103::/64
> nexthop via 2001:db8:1::64
> nexthop dev dummy2
> nexthop via 2001:db8:3::64
>
> In this case the device only route is dropped completely - no notification
> to userpsace but no addition to the FIB either:
>
> $ ip -6 ro ls
> 2001:db8:1::/64 dev dummy1 proto kernel metric 256 pref medium
> 2001:db8:2::/64 dev dummy2 proto kernel metric 256 pref medium
> 2001:db8:3::/64 dev dummy3 proto kernel metric 256 pref medium
> 2001:db8:103::/64 metric 1024
> nexthop via 2001:db8:1::64 dev dummy1 weight 1
> nexthop via 2001:db8:3::64 dev dummy3 weight 1 pref medium
> fe80::/64 dev dummy1 proto kernel metric 256 pref medium
> fe80::/64 dev dummy2 proto kernel metric 256 pref medium
> fe80::/64 dev dummy3 proto kernel metric 256 pref medium
>
> Really, IPv6 multipath is just FUBAR'ed beyond repair when it comes to
> device only routes, so do not allow it all.
>
> This change will break any scripts relying on the mpath api for insert,
> but I don't see any other way to handle the permutations. Besides, since
> the routes are added to the FIB as standalone (non-multipath) routes the
> kernel is not doing what the user requested, so it might as well tell the
> user that.
Yes, I guess we have no real choice for the moment.
Thanks David
Reviewed-by: Eric Dumazet <eduma...@google.com>
