Subject: Re: [PATCH net-next v3] Add Common Applications Kept Enhanced (cake) qdisc

From: Eric Dumazet <[email-masked]>
Date: Wed, 25 Apr 2018 09:00:30 -0700

On 04/25/2018 08:22 AM, Toke Høiland-Jørgensen wrote:
> Eric Dumazet <[email-masked]> writes:

>> Lack of any pskb_may_pull() is really concerning.
> 
> By this you mean "check that the packet is long enough to contain the
> header we are looking for before trying to do ACK filtering", right?

skb->len is not enough, you also have skb->data_len that matters.

A qdisc can be fed with skbs that are not linear, or pretend to be TCP, but they be truncated by malicious sender.

skb might have headers or payload in the page fragments, thus we generally have to call pskb_may_pull()
to bring headers in skb->head

Quite frankly , an ack-filter does not belong to a packet scheduler.

It might be added to tcp conntrack module _if_ someone really cares.