Re: [PATCH net-next] net: vrf: don't down netif when add slave

[Menglong Dong]

On Thu, Jul 31, 2025 at 8:08 PM Ido Schimmel <idosch@xxxxxxxxxx> wrote:
>
> On Thu, Jul 31, 2025 at 07:22:19PM +0800, Menglong Dong wrote:
> > For now, cycle_netdev() will be called to flush the neighbor cache when
> > add slave by downing and upping the slave netdev. When the slave has
> > vlan devices, the data transmission can interrupted.
> >
> > Optimize it by notifying the NETDEV_CHANGEADDR instead, which will also
> > flush the neighbor cache. It's a little ugly, and maybe we can introduce
> > a new event to do such flush :/
>
> Cycling the netdev is not only about neighbors, but also about moving
> routes to the correct table (see the comment above the function):
>
> ip link add name dummy1 up type dummy
> sysctl -wq net.ipv6.conf.dummy1.keep_addr_on_down=1
> ip address add 192.0.2.1/24 dev dummy1
> ip address add 2001:db8:1::1/64 dev dummy1
> ip link add name vrf1 up type vrf table 100
> ip link set dev dummy1 master vrf1
> ip -4 route show table 100
> 192.0.2.0/24 dev dummy1 proto kernel scope link src 192.0.2.1
> local 192.0.2.1 dev dummy1 proto kernel scope host src 192.0.2.1
> broadcast 192.0.2.255 dev dummy1 proto kernel scope link src 192.0.2.1
> ip -6 route show table 100
> local 2001:db8:1::1 dev dummy1 proto kernel metric 0 pref medium
> 2001:db8:1::/64 dev dummy1 proto kernel metric 256 pref medium
> local fe80::f877:f7ff:fecb:bfb dev dummy1 proto kernel metric 0 pref medium
> fe80::/64 dev dummy1 proto kernel metric 256 pref medium
> multicast ff00::/8 dev dummy1 proto kernel metric 256 pref medium
>
> And it doesn't happen with your patch:
>
> ip link add name dummy1 up type dummy
> sysctl -wq net.ipv6.conf.dummy1.keep_addr_on_down=1
> ip address add 192.0.2.1/24 dev dummy1
> ip address add 2001:db8:1::1/64 dev dummy1
> ip link add name vrf1 up type vrf table 100
> ip link set dev dummy1 master vrf1
> ip -4 route show table 100
> ip -6 route show table 100

You are right, something is missing in this patch :/

>
> You can try configuring the VLAN devices with "loose_binding on".

Great! I'll have a try on this param.

Thanks!
Menglong Dong