Gentoo Archives: gentoo-user

From: Ralph Seichter <m16+gentoo@×××××××××××.net>
To: Gentoo User <gentoo-user@l.g.o>
Subject: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12
Date: Sat, 19 Aug 2017 18:28:23
1 It seems strange to me as I write it, but since I updated one of my
2 virtual servers from Kernel version 4.9.34 to 4.12.5, the server (Gentoo
3 Linux running as a KVM guest) is experiencing timeouts when trying to
4 connect to DNS resolvers. For the Kernel update, I followed the same
5 steps I used for years, like
7 cd /usr/src/linux
8 zcat /proc/config.gz >.config
9 make silentoldconfig (answering "no" whereever possible)
10 make ...
12 After booting with Kernel 4.12, commands like "dig +trace"
13 work just fine for a while, duration depending on server load, but after
14 some threshold is passed, all further attempts to contact resolvers fail
15 due to timeouts.
17 I have tried running a local, caching resolver (BIND 9) on the server,
18 like I usually do, and also tried using the hoster's dedicated resolvers.
19 With Kernel 4.12, I see timeouts in both cases. These problems do not
20 occur when I boot with the 4.9 Kernel which I have been using for the
21 past two months.
23 It is also worth noting that I updated two other servers to Kernel 4.12
24 without any issues, but these are "real" servers, not VMs. At this point
25 I am searching for ways to debug the issue, vaguely suspecting some KVM
26 magic behind it (without any proof). I know that Kernel 4.11 introduced
27 several KVM related changes, but that's about it.
29 I appreciate all pointers.
31 -Ralph