Re: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12

[Craig MacKinder <craig@blueshift.net>]

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It sounds like this vmxnet3 bug causing intermittent interface problems
https://bugzilla.kernel.org/show_bug.cgi?id=191201
Try adding this to the VMware guest advanced settings.
vmxnet3.rev.30 = FALSE
And restart the guests.

--
Craig

On Aug 19, 2017, at 11:28 AM, Ralph Seichter <m16+gentoo@monksofcool.net<mailto:m16+gentoo@monksofcool.net>> wrote:

It seems strange to me as I write it, but since I updated one of my
virtual servers from Kernel version 4.9.34 to 4.12.5, the server (Gentoo
Linux running as a KVM guest) is experiencing timeouts when trying to
connect to DNS resolvers. For the Kernel update, I followed the same
steps I used for years, like

 cd /usr/src/linux
 zcat /proc/config.gz >.config
 make silentoldconfig (answering "no" whereever possible)
 make ...

After booting with Kernel 4.12, commands like "dig +trace www.ibm.com<http://www.ibm.com>"
work just fine for a while, duration depending on server load, but after
some threshold is passed, all further attempts to contact resolvers fail
due to timeouts.

I have tried running a local, caching resolver (BIND 9) on the server,
like I usually do, and also tried using the hoster's dedicated resolvers.
With Kernel 4.12, I see timeouts in both cases. These problems do not
occur when I boot with the 4.9 Kernel which I have been using for the
past two months.

It is also worth noting that I updated two other servers to Kernel 4.12
without any issues, but these are "real" servers, not VMs. At this point
I am searching for ways to debug the issue, vaguely suspecting some KVM
magic behind it (without any proof). I know that Kernel 4.11 introduced
several KVM related changes, but that's about it.

I appreciate all pointers.

-Ralph


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