Hi Tom,
On Tue, Oct 27, 2015, at 20:19, Hannes Frederic Sowa wrote:
> On Tue, Oct 27, 2015, at 19:37, Tom Herbert wrote:
> > On Tue, Oct 27, 2015 at 11:29 AM, Hannes Frederic Sowa
> > <han...@stressinduktion.org> wrote:
> > > On Tue, Oct 27, 2015, at 18:32, Tom Herbert wrote:
> > >> On Tue, Oct 27, 2015 at 9:44 AM, Hannes Frederic Sowa
> > >> <han...@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.
> > >
> > Okay, but why bother doing this for net? This problem has obviously
> > existed for a while, and even if the restriction is maintained here
> > there are still other paths that don't go through ip_append_data that
> > could trip the bug. Also, drivers are welcome to fix their issues in
> > net I believe.
>
> I even don't know if it could be a hardware issue. Also I don't want to
> break people's communication with a patch.
> IMHO without the WARN_ON_ONCEs, which I agreed to remove, I currently
> don't see any problem for net.
>
> You don't agree on a netdev-feature flag, indicating the driver is okay
> with hardware checksumming and extension headers? We could add this to
> net-next pretty fast, I think. It does not require people to revert this
> patch in case their driver misbehaves and we don't get a fix for it,
> soon. Also what should we do if the driver simply does not support
> extension headers + checksum offloading? Completely kill checksum
> offloading for IPv6?
I posted v3 just now. I would like to let David consider it for net
inclusion. We can work on how to lift this limitation then in net-next,
okay? I am currently in favor of a new netdev-feature. What do you
think? Your RFC series could help here, too.
Thanks,
Hannes
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