Upcoming 19.07.7 release
baptiste at bitsofnetworks.org
Sun Feb 14 18:21:26 EST 2021
On 07-02-21, Jaap Buurman wrote:
> Are we sure disabling TSO is the actual fix though? There are a few
> reasons I am doubting that assessment:
> 1. Here is a user that is reporting he has always been running with
> TSO disabled, yet he does experience the bug:
> 2. TSO seems fine with the master branch according to user reports.
> 3. The user "mrakotiq" suggested a patch to disable TSO in the bug
> report you linked to, but this bug report also disables
> NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX. The reason that was
> given was that he was seeing packets getting tagged that shouldn't
> have (at least that's what I am understanding from his post on the bug
> report). So there's obviously also something wrong with this
> functionality, and it might not surprise me if this change is the
> thing that seems to fix this issue.
I took time to reproduce this using data from mrakotiq. I could reproduce
the crash, it takes a few hours. Also, disabling NETIF_F_TSO and
NETIF_F_TSO6 indeed makes the crash disappear, at least with this specific
With the patch, performance is a bit lower when forwarding small TCP
packets, but it's still fast enough to reach around 1 Gbit/s with
full-size packets (80 kpps).
Overall, I wouldn't be surprised if the issue is still lurking, but the
patch does seem to improve stability. I'm running a few more tests and I
will add it for the next 19.07 release.
The master branch is fine, but it's using a different driver. It's an
upstream driver, so it probably received more scrutiny than the one used
in 19.07. It should be more reliable to run these devices with 21.02 when
> Having said that, this bug is age-old and is affecting a lot of users,
> me included. So I'd really like to get fixed. If there are no
> regression with this approach, the best way forward might be to simply
> adapt the patch he suggested as a workaround until we're on 21.xx with
> the DSA driver. Especially since this user is reporting no more issues
> with 75 (!) mt7621 routers in his production network, which is a
> rather large sample size. Thoughts?
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