From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id E3BE51396D0 for ; Sat, 19 Aug 2017 18:28:23 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 988121FC06E; Sat, 19 Aug 2017 18:28:17 +0000 (UTC) Received: from ra.horus-it.com (ra.horus-it.com [94.130.34.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 3D0DA1FC044 for ; Sat, 19 Aug 2017 18:28:13 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by ra.horus-it.com (Postfix) with ESMTP id A7E9B48C176D for ; Sat, 19 Aug 2017 20:28:12 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=monksofcool.net; h=content-transfer-encoding:content-language:content-type :content-type:mime-version:user-agent:date:date:message-id :subject:subject:from:from; s=alpha; t=1503167288; x=1505759289; bh=/hoPXVaQAIYRucgteFtGImxkZ6sF9mLbLYlPjF2NGWk=; b=qgxTs99z8TD6 q34s0lTnxPjD8yqiAVeayuxrAnQ6KtL1Vl+dv+qTE2PDD72SdUbN1ewTD3UGKAMJ roqzsPKiN/QHFLwe5IXBOAMfZ54wYPSnDKawjbdEj9gv8vE8oW8nN0LGgs9CBvdr duE2IV1XOrOe4PPh34pYAeWeaT/Oby6wtvdBDs+gooRaTsoQo8oZb1jon/vA6Uxv m525tskAvgR+TM2FVmNZDTMHUvtJyDieOmbnBMV0P3t10JRqLp0wsbpnOgLmq1EU aO2UAvKqyrDfPSXHVVdDe4zSAMK+8RDVdUgvRTclTNGDCqEEApr2uyE52FTgx8PN sbz1E38ZQg== X-Virus-Scanned: at horus-it.com To: Gentoo User From: Ralph Seichter Subject: [gentoo-user] Nameserver lookups fail on virtual server after Kernel upgrade from version 4.9 to 4.12 Message-ID: Date: Sat, 19 Aug 2017 20:28:05 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Archives-Salt: ba04d54e-e620-453f-8d0e-9e528cbddc5a X-Archives-Hash: 0748ee0b506a3790674a08d16c063197 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