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

Mingyen Hsieh (謝明諺)
2025-05-07T01:28:42Z

On Mon, 2025-05-05 at 23:15 +0000, fossben@pm.me wrote:
>
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
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>
> On Monday, May 5th, 2025 at 3:20 AM, fossben@pm.me <fossben@pm.me>
> wrote:
>
> >
> >
> > On Monday, May 5th, 2025 at 12:48 AM, Mingyen Hsieh
> > Mingyen.Hsieh@mediatek.com 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,
> >
> > I manually applied the changes on top of 6.14.5 and mDNS seems to
> > work along with IPv6! I will do more testing for the rest of the
> > day to see if the issue is completely fixed but so far looks good
> > at least for the 5 minutes I've been testing it.
> >
> > Thanks for the fix,
> > Ben
>
> I've now used 6.14.5 with the patch applied for most of the day and
> it's been working great! mDNS has been rock solid and so has IPv6.
>
> Would appreciate it if this fix got backported to the 6.14 series!
>
> Ben

Hi Ben,

Thanks for testing it. And it will be backporting to 6.14 series after
the mainline merged it.

Yen.