Re: [PATCH net v3] vxlan: reject dynamic fdb entries that reference a nexthop id

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski [off-list ref]:

On Thu,  3 Sep 2026 00:59:56 +0900 you wrote:

The commit cited in the Fixes tag allowed VXLAN FDB entries to point to
FDB nexthops so that overlay traffic could be load balanced across
multiple VTEPs. Such entries can only be configured from user space,
cannot be learned and cannot roam. They only make sense with a user space
control plane such as E-VPN where data plane learning is disabled.

Despite that, the VXLAN driver does not currently prevent such entries
from being configured with the "dynamic" flag. The per-nexthop FDB list
is only protected by the per-device hash lock, which is not sufficient
when two VXLAN devices point to the same FDB nexthop and therefore share
the list. Aging runs in softirq context without RTNL, so an entry deleted
by one device can race with an addition or deletion from the other,
leading to list corruption:

[...]

Here is the summary with links:
  - [net,v3] vxlan: reject dynamic fdb entries that reference a nexthop id
    https://git.kernel.org/netdev/net/c/98fc57d16744

You are awesome, thank you!
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