On 10/21/19 12:47 PM, Taehee Yoo wrote:
> Current code doesn't limit the number of nested devices.
> Nested devices would be handled recursively and this needs huge stack
> memory. So, unlimited nested devices could make stack overflow.
>
> This patch adds upper_level and lower_level, they are common variables
> and represent maximum lower/upper depth.
> When upper/lower device is attached or dettached,
> {lower/upper}_level are updated. and if maximum depth is bigger than 8,
> attach routine fails and returns -EMLINK.
>
> In addition, this patch converts recursive routine of
> netdev_walk_all_{lower/upper} to iterator routine.
They were made recursive because of a particular setup. Did you verify
your changes did not break it? See commits starting with
5bb61cb5fd115bed1814f6b97417e0f397da3c79
>
> Test commands:
> ip link add dummy0 type dummy
> ip link add link dummy0 name vlan1 type vlan id 1
> ip link set vlan1 up
>
> for i in {2..55}
> do
> let A=$i-1
>
> ip link add vlan$i link vlan$A type vlan id $i
> done
> ip link del dummy0
8 levels of nested vlan seems like complete nonsense. Why not just limit
that stacking and not mess with the rest which can affect real use cases?
