Date: Fri, 2 Aug 2024 15:52:55 -0700 From: Alex Arslan <ararslan@comcast.net> To: Bakul Shah <bakul@iitbombay.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Diagnosing virtual machine network issues Message-ID: <DB67A5F9-1B15-482F-AD12-0FD4547EC0D0@comcast.net> In-Reply-To: <A9069EB9-2CFE-4A9A-98AD-2C8085873163@comcast.net> References: <FA265FAA-216D-4DCC-92C0-50017C17F7DE@comcast.net> <4a5a177a-5356-453c-8a09-f1d63d5d2e16@sentex.net> <4AB1C33B-DD93-4484-B63A-9FF8FE612B15@comcast.net> <E72DA395-3C66-4520-B58B-31C19E7462A3@comcast.net> <799c7a15-52b8-4b44-bcbd-5ab6a3ef97a6@gmail.com> <0747ED5F-2ED6-461C-9C0B-CFD0EE480D82@comcast.net> <2B0A1E6F-7B89-4F7C-9ECE-ABA94E476D5A@iitbombay.org> <A9069EB9-2CFE-4A9A-98AD-2C8085873163@comcast.net>
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[-- Attachment #1 --] > On Jul 30, 2024, at 2:53 PM, Alex Arslan <ararslan@comcast.net> wrote: > > >> On Jul 30, 2024, at 2:22 PM, Bakul Shah <bakul@iitbombay.org> wrote: >> >>> On Jul 30, 2024, at 2:11 PM, Alex Arslan <ararslan@comcast.net> wrote: >>> >>>> Can you provide more context? I'm not seeing earlier messages anywhere in my email folders. Is this a Qemu issue? >>> >>> The original message is from just over a month ago, archived here: >>> https://lists.freebsd.org/archives/freebsd-hackers/2024-June/003378.html >>> Basically, we have FreeBSD 13.2 VMs running under KVM on a Linux machine. >>> Some code is using libcurl to make a request to an invalid domain and is >>> testing that the error is a resolution failure. This test passes on all >>> platforms except specifically in these FreeBSD VMs; I can't reproduce >>> locally on FreeBSD. That made me think that there's an issue with how the >>> VM was set up, prompting the original message and discussion. Then what >>> I recently found was that we set a 30-second timeout for the libcurl >>> request, which FreeBSD hits in the VM, as it evidently spends a full >>> 30 seconds attempting to resolve the host, while e.g. Linux reports a >>> resolution failure immediately. >> >> What does /etc/resolv.conf look like on the FreeBSD VM? > > > Just a comment and a name server line: > > $ cat /etc/resolv.conf > # Generated by resolvconf > nameserver 192.168.122.1 I believe that is the host IP, so I guess the VM is using the host for DNS resolution? Interestingly, if I add `nameserver 8.8.8.8` below the line with the host IP, it takes 10 seconds rather than 30 to reach the expected domain resolution failure. If I put 8.8.8.8 above the host IP, the domain resolution failure is instantaneous. Not a particularly satisfying conclusion to this saga as I don't understand why it's happening but at least I have a workaround that should hopefully do the job. I really appreciate everyone's help and input thus far! What's the best way to add `nameserver 8.8.8.8` to /etc/resolv.conf as part of the VM's configuration? [-- Attachment #2 --] <html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Jul 30, 2024, at 2:53 PM, Alex Arslan <ararslan@comcast.net> wrote:</div><br class="Apple-interchange-newline"><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><br><div><blockquote type="cite"><div>On Jul 30, 2024, at 2:22 PM, Bakul Shah <bakul@iitbombay.org> wrote:</div><div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">On Jul 30, 2024, at 2:11 PM, Alex Arslan <ararslan@comcast.net> wrote:<br><br><blockquote type="cite">Can you provide more context? I'm not seeing earlier messages anywhere in my email folders. Is this a Qemu issue?<br></blockquote><br>The original message is from just over a month ago, archived here:<br>https://lists.freebsd.org/archives/freebsd-hackers/2024-June/003378.html<br>Basically, we have FreeBSD 13.2 VMs running under KVM on a Linux machine.<br>Some code is using libcurl to make a request to an invalid domain and is<br>testing that the error is a resolution failure. This test passes on all<br>platforms except specifically in these FreeBSD VMs; I can't reproduce<br>locally on FreeBSD. That made me think that there's an issue with how the<br>VM was set up, prompting the original message and discussion. Then what<br>I recently found was that we set a 30-second timeout for the libcurl<br>request, which FreeBSD hits in the VM, as it evidently spends a full<br>30 seconds attempting to resolve the host, while e.g. Linux reports a<br>resolution failure immediately.<br></blockquote><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">What does /etc/resolv.conf look like on the FreeBSD VM?</span></div></blockquote></div><div><br></div>Just a comment and a name server line:<div><br><div><div>$ cat /etc/resolv.conf</div><div># Generated by resolvconf</div><div>nameserver 192.168.122.1</div></div></div></div></div></blockquote><br></div><div><div>I believe that is the host IP, so I guess the VM is using the host for DNS</div><div>resolution? Interestingly, if I add `nameserver 8.8.8.8` below the line</div><div>with the host IP, it takes 10 seconds rather than 30 to reach the expected</div><div>domain resolution failure. If I put 8.8.8.8 above the host IP, the domain</div><div>resolution failure is instantaneous.</div><div><br></div><div>Not a particularly satisfying conclusion to this saga as I don't understand</div><div>why it's happening but at least I have a workaround that should hopefully</div><div>do the job. I really appreciate everyone's help and input thus far!</div><div><br></div><div>What's the best way to add `nameserver 8.8.8.8` to /etc/resolv.conf as</div><div>part of the VM's configuration?</div></div></body></html>help
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