[    2.646795] ip (276) used greatest stack depth: 12320 bytes left
[   21.657030] ip (2138) used greatest stack depth: 12272 bytes left
[  689.494123] blackhole_netdev_xmit(): Dropping skb.
[  689.494189] blackhole_netdev_xmit(): Dropping skb.
[  689.494221] blackhole_netdev_xmit(): Dropping skb.
[  689.494253] blackhole_netdev_xmit(): Dropping skb.
[  953.870062] ip (24596) used greatest stack depth: 12160 bytes left