| 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 |
| 6 |
|
| 7 |
cd /usr/src/linux |
| 8 |
zcat /proc/config.gz >.config |
| 9 |
make silentoldconfig (answering "no" whereever possible) |
| 10 |
make ... |
| 11 |
|
| 12 |
After booting with Kernel 4.12, commands like "dig +trace www.ibm.com" |
| 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. |
| 16 |
|
| 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. |
| 22 |
|
| 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. |
| 28 |
|
| 29 |
I appreciate all pointers. |
| 30 |
|
| 31 |
-Ralph |
Archives