Re: git: 5f11a33ceeb3 - main - if_vlan: do not enable LRO for bridge interaces

I think this may be a better fix, currently untested

diff --git a/sys/net/if_vlan.c b/sys/net/if_vlan.c
index 6aa872a19364..51f0bc63ebda 100644
--- a/sys/net/if_vlan.c
+++ b/sys/net/if_vlan.c
@@ -2074,7 +2074,7 @@ vlan_capabilities(struct ifvlan *ifv)
       if (p->if_capabilities & IFCAP_VLAN_HWCSUM)
               cap |= p->if_capabilities & IFCAP_LRO;
       if (p->if_capenable & IFCAP_VLAN_HWCSUM)
-               ena |= p->if_capenable & IFCAP_LRO;
+               ena |= mena & IFCAP_LRO;

       /*
        * If the parent interface can offload TCP connections over VLANs then

On Fri, Aug 11, 2023 at 5:07 PM Kevin Bowling <kevin.bowling@kev009.com> wrote:
>
> I am wondering what is going on with this patch, it doesn't seem like
> a full fix.  At the very least we should clean up the "can't disable
> some capabilities" message.
>
> I've been looking at this for a couple hours and am wondering what is
> going on in if_bridge.. it looks like it correctly loops over the
> interfaces and masks ifcaps it doesn't like using the interface's
> ioctl SIOCSIFCAP.  A similar pattern is used in if_lagg.  I don't see
> any issue there so far.  I also don't see the SIOCSICAP ioctl failing
> nor did vixie's message report that.
>
> I checked on a cxgbe(9) bridged vlan setup I have and see this message
> "bridge0: can't disable some capabilities on vlan0: 0x400"
>
> So I am wondering if the bug is that if_vlan SIOCSIFCAP is
> disregarding the ioctl's request mask.. it is just blindly calling
> vlan_capabilities.
>
> Regards,
> Kevin
>
>
> On Fri, Aug 11, 2023 at 3:51 PM Kristof Provost <kp@freebsd.org> wrote:
> >
> > The branch main has been updated by kp:
> >
> > URL: https://cgit.FreeBSD.org/src/commit/?id=5f11a33ceeb385477cb22d9ad5941061c5a26be9
> >
> > commit 5f11a33ceeb385477cb22d9ad5941061c5a26be9
> > Author:     Paul Vixie <paul@redbarn.org>
> > AuthorDate: 2023-08-11 18:17:16 +0000
> > Commit:     Kristof Provost <kp@FreeBSD.org>
> > CommitDate: 2023-08-11 22:50:37 +0000
> >
> >     if_vlan: do not enable LRO for bridge interaces
> >
> >     If the parent interface is not a bridge and can do LRO and
> >     checksum offloading on VLANs, then guess it may do LRO on VLANs.
> >     False positive here cost nothing, while false negative may lead
> >     to some confusions. According to Wikipedia:
> >
> >     "LRO should not operate on machines acting as routers, as it breaks
> >     the end-to-end principle and can significantly impact performance."
> >
> >     The same reasoning applies to machines acting as bridges.
> >
> >     PR:             254596
> >     MFC after:      3 weeks
> > ---
> >  sys/net/if_vlan.c | 22 +++++++++++++++-------
> >  1 file changed, 15 insertions(+), 7 deletions(-)
> >
> > diff --git a/sys/net/if_vlan.c b/sys/net/if_vlan.c
> > index 6aa872a19364..92e4e4247e3d 100644
> > --- a/sys/net/if_vlan.c
> > +++ b/sys/net/if_vlan.c
> > @@ -2067,14 +2067,22 @@ vlan_capabilities(struct ifvlan *ifv)
> >         }
> >
> >         /*
> > -        * If the parent interface can do LRO and checksum offloading on
> > -        * VLANs, then guess it may do LRO on VLANs.  False positive here
> > -        * cost nothing, while false negative may lead to some confusions.
> > +       * If the parent interface is not a bridge and can do LRO and
> > +       * checksum offloading on VLANs, then guess it may do LRO on VLANs.
> > +       * False positive here cost nothing, while false negative may lead
> > +       * to some confusions. According to Wikipedia:
> > +       *
> > +       * "LRO should not operate on machines acting as routers, as it breaks
> > +       * the end-to-end principle and can significantly impact performance."
> > +       *
> > +       * The same reasoning applies to machines acting as bridges.
> >          */
> > -       if (p->if_capabilities & IFCAP_VLAN_HWCSUM)
> > -               cap |= p->if_capabilities & IFCAP_LRO;
> > -       if (p->if_capenable & IFCAP_VLAN_HWCSUM)
> > -               ena |= p->if_capenable & IFCAP_LRO;
> > +       if (ifp->if_bridge == NULL) {
> > +               if (p->if_capabilities & IFCAP_VLAN_HWCSUM)
> > +                       cap |= p->if_capabilities & IFCAP_LRO;
> > +               if (p->if_capenable & IFCAP_VLAN_HWCSUM)
> > +                       ena |= p->if_capenable & IFCAP_LRO;
> > +       }
> >
> >         /*
> >          * If the parent interface can offload TCP connections over VLANs then
> >