Re: [PATCH net v2 3/4] ipv6: no CHECKSUM_PARTIAL on MSG_MORE corked sockets

[Hannes Frederic Sowa <hannes@stressinduktion.org>]

On Tue, Oct 27, 2015, at 18:32, Tom Herbert wrote:
> On Tue, Oct 27, 2015 at 9:44 AM, Hannes Frederic Sowa
> <hannes@stressinduktion.org> wrote:
> >
> >
> > On Tue, Oct 27, 2015, at 17:36, Tom Herbert wrote:> > -               if
> > (cork->length + length > maxnonfragsize - headersize) {
> >> > +       if (cork->length + length > maxnonfragsize - headersize) {
> >> >  emsgsize:
> >> > -                       ipv6_local_error(sk, EMSGSIZE, fl6,
> >> > -                                        mtu - headersize +
> >> > -                                        sizeof(struct ipv6hdr));
> >> > -                       return -EMSGSIZE;
> >> > -               }
> >> > +               ipv6_local_error(sk, EMSGSIZE, fl6,
> >> > +                                mtu - headersize +
> >> > +                                sizeof(struct ipv6hdr));
> >> > +               return -EMSGSIZE;
> >> >         }
> >> >
> >> > +       /* CHECKSUM_PARTIAL only with no extension headers and when
> >>
> >> No, please don't do this. CHECKSUM_PARTIAL should work with extension
> >> headers as defined, so this is just disabling otherwise valid and
> >> useful functionality. If (some) drivers have problems with this they
> >> need to be identified and fixed.
> >
> > I don't understand. The old code already didn't allow the use of
> > opt_flen with CHECKSUM_PARTIAL.
> >
> Then that's a problem with the old code :-). Is there any other reason
> that we can't use CHECKSUM_PARTIAL with extension headers other than
> lack of correct driver support?

The lack of correct driver support is a big bumper, but as I wrote, I
don't see a reason to not lift this restriction in net-next. I proposed
a new feature flag, or by looking at your series, we could probably use
the extension header okay field for that.

I would be conservative in net though.

Bye,
Hannes