Subject: Re: [PATCH net] netlink: fix netlink_ack with large messages

From: Jamal Hadi Salim <[email-masked]>
Date: Sat, 09 Nov 2013 08:43:51 -0500

On 11/09/13 00:00, David Miller wrote:

> The user has the message, they gave it to us in the sendmsg()
> we are responding to.  We absolutely do not need to give it
> to them again.
>
> If they care about referring to the contents of that message, they can
> refer to it in their own copy and make sure they are really looking at
> the same thing by comparing the sequence number in the netlink ACK to
> the one they used in the netlink header they gave to the kernel in the
> sendmsg() call.
>
> What happens now is pure duplication, and for such huge netlink
> messages it's really not smart at all.
>

for errors, we need to give the user something back. This has been the
behavior for 80 years now. Giving them a HUGE message
back is rediculuos(tm). Ive had enough of SCTP doing that.
We need to cap it - sort of what ICMP does.
ICMP caps at 64B; something like 128B is reasonable.

cheers,
jamal