Re: Documentation question

[Duncan Roe <duncan_roe@optusnet.com.au>]

On Sat, Dec 21, 2019 at 09:43:45PM +1100, Duncan Roe wrote:
> On Fri, Dec 20, 2019 at 01:29:53AM +0100, Pablo Neira Ayuso wrote:
> > On Sun, Dec 15, 2019 at 01:02:20PM +1100, Duncan Roe wrote:
> > > Hi Pablo,
> > >
> > > In pktbuff.c, the doc for pktb_mangle states that "It is appropriate to use
> > > pktb_mangle to change the MAC header".
> > >
> > > This is not true. pktb_mangle always mangles from the network header onwards.
> > >
> > > I can either:
> > >
> > > Whithdraw the offending doc items
> > >
> > > OR:
> > >
> > > Adjust pktb_mangle to make the doc correct. This involves changing pktb_mangle,
> > > nfq_ip_mangle and (soon) nfq_ip6_mangle. The changes would be a no-op for
> > > AF_INET and AF_INET6 packet buffers.
> > >
> > > What do you think?
> >
> > You could fix it through signed int dataoff. So the users could
> > specify a negative offset to mangle the MAC address.
> >
> > This function was made to update layer 7 payload information to
> > implement the helpers. So dataoff usually contains the transport
> > header size.
> >
> > Let me know, thanks.
> >
> -ve offsets? There has to be a better way.
>
> When I added documentation for pktb_mangle, I assumed it mangled from
> pktb->data, rather than checking the source.
>
> That is the function I documented, and I think we need a function like that.
>
> Rather than change the behaviour of pktb_mangle when a MAC header is present, I
> propose a new function pktb_mangle2 which mangles from pktb->data onwards.
>
> pktb_mangle would call this new function, with dataoff incremented by
> pktb->network_header - pktb->data (only nonzero for AF_BRIDGE)
>
> Ok?
>
> Cheers ... Duncan.
>
On second thoughts, I'll just do the signed offset thing and have done with it.
Hope you can accept it quickly: I'll base it on master so you can apply it
before considering the pktb_usebuf() patch.