Re: pskb change in dst->output

["David S. Miller" <davem@xxxxxxxxxx>]

On Thu, 8 Jul 2004 07:28:05 +1000
Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

> OK.  Can you please tell me which caller of dst_output() passes
> a cloned skb to it?
> 
> I need to know this because if this is the case, we need fix the various
> IPsec output functions to copy the skb.

They do already, via skb_cow().

The case James's patch tries to deal with is when multicast
loops back packets to localhost, see ip_mc_output().
Since the SKB is a clone, if we do anything with the checksum
state of the clone, this messes up the hw checksumming state
of the original SKB and we get output packets with corrupt
checksums.