On Mon, Jun 13, 2005 at 02:48:10PM +1000, Herbert Xu wrote: > On Sun, Jun 12, 2005 at 04:24:01PM +0200, Willy Tarreau wrote: > > > > 1) no firewall in front of A > > - C spoofs A and sends a fake SYN to B > > - B responds to A with a SYN-ACK > > - A sends an RST to B, which clears the session > > - A wants to connect and sends its SYN to B which accepts it. > > Well the attacker simply has to keep sending the same SYN packet > over and over again until A runs out of SYN retries. > > What I really don't like about your patch is the fact that it is > trying to impose a policy decision (that of forbidding all > simultaneous connection initiations) inside the TCP stack. It's the same for ECN or SYN cookies. > A much better place to do that is netfilter. If you do it there > then not only will your protect all Linux machines from this attack, > but you'll also protect all the other BSD-derived TCP stacks. Netfilter already blocks simultaneous connection. A SYN in return to a SYN produces an INVALID state. Cheers, Willy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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