Re: [tcpm] TCP Long Options - Why not as payload in SYNs?

["Caitlin Bestler" <[e-mail]>]

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf
Of
> Michael Scharf
> Sent: Monday, July 14, 2008 5:14 AM
> To: [e-mail]
> Subject: [tcpm] TCP Long Options - Why not as payload in SYNs?
> 
> Hi all,
> 
> I wonder whether "modern" TCP stacks indeed process application
> payload data in SYN segments.
> 
> Even though RFC 793 explicitly allows payload in SYN segments, there
> are TCP stacks that just seem to ignore it. Couldn't this offer an
> opportunity to transport long TCP options in the payload of SYN
> segments, instead of expanding the header option space?
> 
> Sorry if this question has already been answered elsewhere.
> 
> Michael

Any stack that uses SYN Cookies, or wants the option to, will reject
any SYN that has payload.

If a stack were to decide to accept SYNs with Payload as part of an
optional enhancement then it would need a new method of defending from
SYN floods. Generally, any stack that obligates itself to retain state
in its memory on the basis of a single received SYN is a sitting duck
for a Denial of Service attack.

_______________________________________________
tcpm mailing list
[e-mail]
https://www.ietf.org/mailman/listinfo/tcpm