From: Duncan Roe <duncan_roe@optusnet.com.au>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Netfilter Development <netfilter-devel@vger.kernel.org>
Subject: Re: Documentation question
Date: Sat, 21 Dec 2019 21:43:45 +1100 [thread overview]
Message-ID: <20191221104345.GA10475@dimstar.local.net> (raw)
In-Reply-To: <20191220002953.gv25rcn7kvv43zk4@salvia>
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.
next prev parent reply other threads:[~2019-12-21 10:44 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-15 2:02 Documentation question Duncan Roe
2019-12-20 0:29 ` Pablo Neira Ayuso
2019-12-21 10:43 ` Duncan Roe [this message]
2019-12-22 2:23 ` Duncan Roe
2019-12-22 3:36 ` [PATCH libnetfilter_queue] src: pktb_mangle has signed offset arg so can mangle MAC header with -ve one Duncan Roe
2019-12-30 11:38 ` Pablo Neira Ayuso
-- strict thread matches above, loose matches on Subject: below --
2021-07-04 23:45 Documentation question Duncan Roe
2021-07-05 8:56 ` Pablo Neira Ayuso
2021-07-05 13:13 ` Duncan Roe
2021-07-05 14:42 ` Pablo Neira Ayuso
2019-11-20 23:09 Duncan Roe
2019-11-20 23:26 ` Florian Westphal
2019-11-21 5:33 ` Duncan Roe
2019-10-30 9:07 Duncan Roe
2019-10-30 9:15 ` Pablo Neira Ayuso
2019-10-30 9:38 ` Duncan Roe
2019-10-30 9:47 ` Pablo Neira Ayuso
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