Re: [REGRESSION][BISECTED][STABLE] MT7925: mDNS and IPv6 broken in kernel 6.14.3 and above

Mingyen Hsieh (謝明諺)
2025-05-07T01:27:21Z

On Mon, 2025-05-05 at 19:18 +0200, Niklas Schnelle wrote:
>
> External email : Please do not click links or open attachments until
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>
> On Mon, 2025-05-05 at 05:48 +0000, Mingyen Hsieh (謝明諺) wrote:
> > On Sun, 2025-05-04 at 00:39 +0200, Niklas Schnelle wrote:
> > >
> > > External email : Please do not click links or open attachments
> > > until
> > > you have verified the sender or the content.
> > >
> > >
> > > On Wed, 2025-04-30 at 06:47 +0000, Mingyen Hsieh (謝明諺) wrote:
> > > > On Wed, 2025-04-30 at 01:14 +0000, fossben@pm.me wrote:
> > > > >
> > > > > External email : Please do not click links or open
> > > > > attachments
> > > > > until
> > > > > you have verified the sender or the content.
> > > > >
> > > > >
> > > > > Hello all,
> > > > >
> > > > > After upgrading to 6.14.3 on my PC with a MT7925 chip, I
> > > > > noticed
> > > > > that
> > > > > I could no longer ping *.local addresses provided by Avahi.
> > > > > In
> > > > > addition, I also noticed that I was not able to get a DHCP
> > > > > IPv6
> > > > > address from my router, no matter how many times I rebooted
> > > > > the
> > > > > router or reconnected with NetworkManager.
> > > > >
> > > > > Reverting to 6.14.2 fixes both mDNS and IPv6 addresses
> > > > > immediately.
> > > > > Going back to 6.14.3 immediately breaks mDNS again, but the
> > > > > IPv6
> > > > > address will stay there for a while before disappearing
> > > > > later,
> > > > > possibly because the DHCP lease expired? I am not sure
> > > > > exactly
> > > > > when
> > > > > it stops working.
> > > > >
> > > > > I've done a kernel bisect between 6.14.2 and 6.14.3 and found
> > > > > the
> > > > > offending commit that causes mDNS to fail:
> > > > >
> > > > > commit 80007d3f92fd018d0a052a706400e976b36e3c87
> > > > > Author: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
> > > > > Date:   Tue Mar 4 16:08:50 2025 -0800
> > > > >
> > > > >     wifi: mt76: mt7925: integrate *mlo_sta_cmd and *sta_cmd
> > > > >
> > > > >     commit cb1353ef34735ec1e5d9efa1fe966f05ff1dc1e1 upstream.
> > > > >
> > > > >     Integrate *mlo_sta_cmd and *sta_cmd for the MLO firmware.
> > > > >
> > > > >     Fixes: 86c051f2c418 ("wifi: mt76: mt7925: enabling MLO
> > > > > when
> > > > > the
> > > > > firmware supports it")
> > > > >
> > > > >  drivers/net/wireless/mediatek/mt76/mt7925/mcu.c | 59 ++++---
> > > > > ----
> > > > > ----
> > > > > --------------------------------------------
> > > > >  1 file changed, 4 insertions(+), 55 deletions(-)
> > > > >
> > > > > I do not know if this same commit is also causing the IPv6
> > > > > issues
> > > > > as
> > > > > testing that requires quite a bit of time to reproduce. What
> > > > > I do
> > > > > know with certainty as of this moment is that it definitely
> > > > > breaks in
> > > > > kernel 6.14.3.
> > > > >
> > > > > I've attached my hardware info as well as dmesg logs from the
> > > > > last
> > > > > working kernel from the bisect and 6.14.4 which exhibits the
> > > > > issue.
> > > > > Please let me know if there's any other info you need.
> > > > >
> > > > > Thanks!
> > > > > Benjamin Xiao
> > > >
> > > > Hi,
> > > >
> > > > Thanks for reporting this issue, we will aim into this.
> > > >
> > > > Can you provide me with your testing steps?
> > > >
> > > > Best Regards,
> > > > Yen.
> > > >
> > >
> > > Hi Yan,
> > >
> > > I see the same IPv6 issue on my Framework 13 (Ryzen 5 AI 340)
> > > with an
> > > mt7925e WiFI module. My setup is just a home router with native
> > > IPv6
> > > both for my uplink and in the LAN. The problems with IPv6 can
> > > already
> > > be seen just in the LAN for example by checking which IP was used
> > > for
> > > SSH, in my setup it should always be IPv6 but falls back to IPv4
> > > in
> > > the
> > > broken state.
> > >
> > > As another data point, I tried reverting cb1353ef3473 ("wifi:
> > > mt76:
> > > mt7925: integrate *mlo_sta_cmd and *sta_cmd") on top of 6.15.-
> > > rc4.
> > > This
> > > fully restores IPv6 for me. Also note I'm running this with the
> > > mt7925
> > > firmware version 20250425073330 from linux-firmware's master
> > > branch
> > > as
> > > I had some dropped connections with earlier firmware.
> > >
> > > So it definitely looks like that commit also broke IPv6 and not
> > > just
> > > mDNS. Note that if if I use DHCPv6 instead of router
> > > advertisements,
> > > on
> > > the latest firmware, but without the revert, I get a global IPv6
> > > address added to the interface but then native IPv6 addresses are
> > > still
> > > uncreachable. With the offending patch reverted my SSH session to
> > > an
> > > IPv6 only host works fine and is stable. Also I'd be willing to
> > > test
> > > a
> > > proper fix as I rely on IPv6 heavily due to having to use CGNAT
> > > for
> > > IPv4 but not for IPv6.
> > >
> > >
> > > Thanks,
> > > Niklas
> >
> > Hi Benjamin & Niklas,
> >
> > Can you help to try this patch? I can get IPv6 address through this
> > patch.
> >
> > If it can work at your environment as well, i will upstream it and
> > add
> > test tag with you.
> >
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > index a42b584634ab..fd756f0d18f8 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > @@ -2183,14 +2183,14 @@ mt7925_mcu_sta_cmd(struct mt76_phy *phy,
> >                         mt7925_mcu_sta_mld_tlv(skb, info->vif,
> > info-
> > > link_sta->sta);
> >                         mt7925_mcu_sta_eht_mld_tlv(skb, info->vif,
> > info->link_sta->sta);
> >                 }
> > -
> > -               mt7925_mcu_sta_hdr_trans_tlv(skb, info->vif, info-
> > > link_sta);
> >         }
> >
> >         if (!info->enable) {
> >                 mt7925_mcu_sta_remove_tlv(skb);
> >                 mt76_connac_mcu_add_tlv(skb, STA_REC_MLD_OFF,
> >                                         sizeof(struct tlv));
> > +       } else {
> > +               mt7925_mcu_sta_hdr_trans_tlv(skb, info->vif, info-
> > > link_sta);
> >         }
> >
> >         return mt76_mcu_skb_send_msg(dev, skb, info->cmd, true);
> >
> >
> > Thanks~
> > Yen.
> >
>
> Hi Yen,
>
> As the patch didn't apply, I edited mt7925_mcu_sta_cmd() manually on
> top of v6.15-rc5 according to the diff. With that IPv6 works fine for
> me.
>

Hi Niklas,

Thanks for testing.

> If it were me, I'd probably structure the if different. I'd leave
> the mt7925_mcu_sta_hdr_trans_tlv() where it is but have an inner if
> (info->link_sta) inside just if (!info->enable), then the !info-
> >enable
> case becomes just an else. I'd maybe even put the if (info->link_sta)
> body in its own static function if that makes sense semantically, but
> I
> don't know enough (anything) about the driver to know. Anyway, that's
> all a matter of taste and actually makes the patch quite a bit
> larger.
>

I will consider about this approach and try to release the patch within
the next few days.

> So whichever way you decide on feel free to add:
>
> Tested-by: Niklas Schnelle <niks@kernel.org>
>
> Thanks,
> Niklas