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" 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
