<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hello,<div class=""><br class=""></div><div class=""><br class=""></div><div class="">[If you don’t use VNC to access a Linux host, you can safely skip this e-mail]</div><div class=""><br class=""></div><div class="">I recently lost access to three Linux hosts over VNC, and it took me long enough to figure out what was going on that I thought I’d share and ask for advice. This is recorded as <a href="https://bugzilla.redhat.com/show_bug.cgi?id=1437619" class="">https://bugzilla.redhat.com/show_bug.cgi?id=1437619</a>, seems to be related to others, e.g. <a href="https://bugzilla.redhat.com/show_bug.cgi?id=703009" class="">https://bugzilla.redhat.com/show_bug.cgi?id=703009</a>.</div><div class=""><br class=""></div><div class="">Symptoms: VNC access to a Linux host does not work. Local access with remote-viewer <a href="vnc://localhost:5900" class="">vnc://localhost:5900</a> works. Remote access with remote-viewer <a href="vnc://myhost:5900" class="">vnc://myhost:5900</a> does not. Doing lsof -i -P | grep vino shows that the vino-server is only listening to IPv6.</div><div class=""><br class=""></div><div class="">Apparent cause: In some conditions, which apparently involve localhost resolving as ::1, vino-server only listens to IPv6. When this is the case, you get:</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">ddd@muse ~> lsof -i -R | grep vino</span></div><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ff3b1e" class="">vino</span><span style="font-variant-ligatures: no-common-ligatures" class="">-serv 3326 1309 ddd 12u IPv6 75662 0t0 TCP *:rfb (LISTEN)</span></div></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class="">When it’s working “normally”, you get:</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">ddd@muse ~> lsof -i -R | grep vino</span></div><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ff3b1e" class="">vino</span><span style="font-variant-ligatures: no-common-ligatures" class="">-serv 3326 1309 ddd 12u IPv4 86485 0t0 TCP <a href="http://muse.dinechin.org" class="">muse.dinechin.org</a>:rfb (LISTEN)</span></div><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ff3b1e" class="">vino</span><span style="font-variant-ligatures: no-common-ligatures" class="">-serv 3326 1309 ddd 14u IPv6 86486 0t0 TCP <a href="http://muse.dinechin.org" class="">muse.dinechin.org</a>:rfb (LISTEN)</span></div><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ff3b1e" class="">vino</span><span style="font-variant-ligatures: no-common-ligatures" class="">-serv 3326 1309 ddd 15u IPv6 86487 0t0 TCP <a href="http://muse.dinechin.org" class="">muse.dinechin.org</a>:rfb (LISTEN)</span></div><div style="margin: 0px; font-size: 10px; line-height: normal; font-family: Monaco; background-color: rgba(255, 255, 255, 0.901961);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ff3b1e" class="">vino</span><span style="font-variant-ligatures: no-common-ligatures" class="">-serv 3326 1309 ddd 16u IPv4 86488 0t0 TCP <a href="http://muse.dinechin.org" class="">muse.dinechin.org</a>:rfb->192.168.77.22:54781 (ESTABLISHED)</span></div></span></div><div class=""><br class=""></div><div class="">Workaround: I found two workarounds. You may need one or both, I’ve not seen consistent results between my hosts.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>#1: Disable localhost resolution to ::1. In my case, this means:</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>a) Removing the resolution in my local DNS, in my case it was in /etc/bind/db.local</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>b) Commenting out the ::1 entry in /etc/hosts.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>#2: Force the server to listen on a specific interface (only had to do it on one of my hosts)</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>a) Run dconf-editor</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>b) Go to /org/gnome/desktop/remote-access/network-interface</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>c) Set “Use default value” to off</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>d) Enter the name of your network card, e.g. enp4s0 for my machine, in the “Custom value” field.</div><div class=""><br class=""></div><div class="">Cause of change: I am not sure, because I changed both my DNS (now bind9 on a local machine) and did a dnf update. I saw the problem after the update, but it may just be because the network restarted, since in at least one case, vino-server had not actually been updated.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Hope this helps someone ;-)</div><div class=""><br class=""></div><div class="">Christophe</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></body></html>