Re: [PATCH nft 1/2] src: add dscp support

[Patrick McHardy <kaber@trash.net>]

On 25.11, Pablo Neira Ayuso wrote:
> On Wed, Nov 25, 2015 at 08:45:13PM +0000, Patrick McHardy wrote:
> > On 25.11, Pablo Neira Ayuso wrote:
> > > On Wed, Nov 25, 2015 at 08:01:25PM +0000, Patrick McHardy wrote:
> > > > On 25.11, Pablo Neira Ayuso wrote:
> > > > >  #define TYPE_MAX		(__TYPE_MAX - 1)
> > > > > diff --git a/include/proto.h b/include/proto.h
> > > > > index a43bf98..41af0c1 100644
> > > > > --- a/include/proto.h
> > > > > +++ b/include/proto.h
> > > > > @@ -176,7 +176,7 @@ enum ip_hdr_fields {
> > > > >  	IPHDR_INVALID,
> > > > >  	IPHDR_VERSION,
> > > > >  	IPHDR_HDRLENGTH,
> > > > > -	IPHDR_TOS,
> > > > > +	IPHDR_DSCP,
> > > > 
> > > > Shouldn't we keep both? I think it should work to do that or at least not be
> > > > difficult to make it work.
> > > 
> > > Last time we discussed this, people arised concerns related to the
> > > fact that this is obsolete, and nobody should be using this these
> > > days.
> > 
> > I don't really buy into these arguments. We support lots of obsolete things,
> > the fact is that even though it is obsoleted, it still exists and for old
> > devices might even be the only thing they support.
> 
> ToS breaks useful things like ECN, and the more I keep reading docs on
> the Internet, the more problem I have to see how the user can benefit
> from this.

We *match* on ToS, that cannot possibly break anything. Also I'm unsure how
this could break ECN even otherwise, ToS does not even use the ECN bits.

Its quite simple, if the user has old devices that set ToS values, he will
be able to match on that without manually converting it to DSCP values.
Given that our current tos definition is also not to practical for that
since its too broad, I don't really care that much, although I think it
should rather be fixed than simply thrown out.