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

[Mingyen Hsieh (謝明諺)]

On Sun, 2025-05-04 at 00:39 +0200, Niklas Schnelle wrote:
> 
> External email : Please do not click links or open attachments until
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> 
> 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 at 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 at 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.