Re: zero-copy TCP

From: Andi Kleen (
Date: Sun Sep 03 2000 - 12:56:39 EST

On Sun, Sep 03, 2000 at 07:42:53PM +0200, Ingo Molnar wrote:
> On Sun, 3 Sep 2000, Andi Kleen wrote:
> > You can already cause incorrect checksums on the wire just by passing
> > a partly unmapped address (the zero-the-rest exception handler in
> > csum_copy_generic in i386 forgets to add in the carry)
> >
> > I do not believe it is a big deal, packets with bad checksum are not
> > really a problem (you can usually do other better DoS that do not need
> > it)
> i think it's a quality of implementation issue. The csum_copy_generic
> thing is a bug. Allowing incorrect checksums to be sent out would be a

>From brief inspection at least arm, mips, m68k have similar problems.

[haven't checked the others]

> design bug. I think some RFCs do even forbid the sending of incorrect
> packets?

I do not know any that do. Of course you shouldn't, but the receiver
has to handle it anyways.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
Please read the FAQ at

This archive was generated by hypermail 2b29 : Thu Sep 07 2000 - 21:00:15 EST