Re: pskb change in dst->output

[James Morris <jmorris@xxxxxxxxxx>]

On Thu, 8 Jul 2004, Herbert Xu wrote:

> I'm just a bit unsure whether the pskb change is needed in dst_output().

Ok, dst_output() iterates over the skb->dst stack:

        for (;;) {
                err = skb->dst->output(&skb);

                if (likely(err == 0))
                        return err;
                if (unlikely(err != NET_XMIT_BYPASS))
                        return err;
        }

We need to pass a pointer to skb to skb->dst->output() because the skb can
be changed by skb_checksum_help() in one of these output paths.  Further
iteration would otherwise pass an incorrect (freed) skb.

The change to dst->output() which implements a double skb pointer is then
propagated throughout the code, e.g.  ah_output() has to change because it
becomes an output function via xfrm->type->output().


- James
-- 
James Morris
<jmorris@xxxxxxxxxx>