Re: [PATCH net] ipv6: tcp: drop silly ICMPv6 packet too big messages

Hi Eric,

On Wed, Jul 07, 2021 at 08:46:30AM -0700, Eric Dumazet wrote:

From: Eric Dumazet <edumazet@google.com>

While TCP stack scales reasonably well, there is still one part that
can be used to DDOS it.

IPv6 Packet too big messages have to lookup/insert a new route,
and if abused by attackers, can easily put hosts under high stress,
with many cpus contending on a spinlock while one is stuck in fib6_run_gc()

Just thinking loud, wouldn't it make sense to support randomly dropping
such packets on input (or even better rate-limit them) ? After all, if
a host on the net feels like it will need to send one, it will surely
need to send a few more until one is taken into account so it's not
dramatic. And this could help significantly reduce their processing cost.

Willy