Gentoo Archives: gentoo-user

From: Neil Bothwick <neil@××××.net>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12
Date: Sun, 20 Aug 2017 06:17:30
Message-Id: E40D0B22-59F3-4EB5-87DE-26C677C3DD33@stfw.net
In Reply to: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12 by Ralph Seichter
1 I'd try again with a clean kernel tree but using make oldconfig. It's possible the automagic stuff answered n somewhere where you need a y.
2
3 On 19 August 2017 21:28:05 EEST, Ralph Seichter <m16+gentoo@×××××××××××.net> wrote:
4 >It seems strange to me as I write it, but since I updated one of my
5 >virtual servers from Kernel version 4.9.34 to 4.12.5, the server
6 >(Gentoo
7 >Linux running as a KVM guest) is experiencing timeouts when trying to
8 >connect to DNS resolvers. For the Kernel update, I followed the same
9 >steps I used for years, like
10 >
11 > cd /usr/src/linux
12 > zcat /proc/config.gz >.config
13 > make silentoldconfig (answering "no" whereever possible)
14 > make ...
15 >
16 >After booting with Kernel 4.12, commands like "dig +trace www.ibm.com"
17 >work just fine for a while, duration depending on server load, but
18 >after
19 >some threshold is passed, all further attempts to contact resolvers
20 >fail
21 >due to timeouts.
22 >
23 >I have tried running a local, caching resolver (BIND 9) on the server,
24 >like I usually do, and also tried using the hoster's dedicated
25 >resolvers.
26 >With Kernel 4.12, I see timeouts in both cases. These problems do not
27 >occur when I boot with the 4.9 Kernel which I have been using for the
28 >past two months.
29 >
30 >It is also worth noting that I updated two other servers to Kernel 4.12
31 >without any issues, but these are "real" servers, not VMs. At this
32 >point
33 >I am searching for ways to debug the issue, vaguely suspecting some KVM
34 >magic behind it (without any proof). I know that Kernel 4.11 introduced
35 >several KVM related changes, but that's about it.
36 >
37 >I appreciate all pointers.
38 >
39 >-Ralph
40
41 --
42 Sent from my Android device with K-9 Mail. Please excuse my brevity.

Replies

Subject Author
Re: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12 Ralph Seichter <m16+gentoo@×××××××××××.net>