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SubjectRe: T/TCP: Syn and RST Cookies
On Mon, Apr 13, 1998 at 06:56:16PM +0200, David S. Miller wrote:
> From: Andi Kleen <ak@muc.de>
> Date: 13 Apr 1998 17:49:52 +0200
>
> "David S. Miller" <davem@dm.cobaltmicro.com> writes:
>
> > We drop data in a SYN frame, relax pinhead.
>
> We could make it a sysctl. For all usual cases it would be no
> slowdown in the critical path, because that part is never hit
> anyways by SYNs without data.
>
> Nope, ain't gonna happen. Alan in his commentary was trying to hint
> that allowing this to happen can open you to certain DoS attacks.

I should have writen: a sysctl, with the default to off, for better
T/TCP interoperability for people in intranets where they don't care
too much about DOS attacks.

Another point: we could limit the maximal data sized queued with the SYN -
as long as sizeof(struct open_request) + maxpacketsize <= sizeof(struct sock)
the situation is not worse than with stock 2.0 without syncookies ;)

T/TCP is often nice for small transactions where only a few bytes need
to be reliably transfered. This check would allow that nicely.


-Andi


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