[Bug 1752411] Re: bind9-host, avahi-daemon-check-dns.sh hang forever causes network connections to get stuck
1752411 at bugs.launchpad.net
Wed Aug 29 09:25:03 UTC 2018
The suggested mitigation is in bionic-unapproved for the consideration
of the SRU team.
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bind9-host, avahi-daemon-check-dns.sh hang forever causes network
connections to get stuck
Status in avahi package in Ubuntu:
Status in bind9 package in Ubuntu:
Status in openconnect package in Ubuntu:
Status in strongswan package in Ubuntu:
Status in avahi source package in Bionic:
Status in bind9 source package in Bionic:
Status in avahi source package in Cosmic:
Status in bind9 source package in Cosmic:
Status in avahi package in Debian:
* Network connections for some users fail (in some cases a direct
interface, in others when connecting a VPN) because the 'host' command
to check for .local in DNS called by /usr/lib/avahi/avahi-daemon-
check-dns.sh never times out like it should - leaving the script
hanging indefinitely blocking interface up and start-up. This appears
to be a bug in host caused in some circumstances however we implement
a workaround to call it under 'timeout' as the issue with 'host' has
not easily been identified, and in any case acts as a fall-back.
* Multiple people have been unable to create a reproducer on a
generic machine (e.g. it does not occur in a VM), I have a specific
machine I can reproduce it on (a Skull Canyon NUC with Intel I219-LM)
by simply "ifdown br0; ifup br0" and there are clearly 10s of other
users affected in varying circumstances that all involve the same
symptoms but no clear test case exists. Best I can suggest is that I
test the patch on my system to ensure it works as expected, and the
change is only 1 line which is fairly easily auditible and
* The change is a single line change to the shell script to call host with "timeout". When tested on working and non-working system this appears to function as expected. I believe the regression potential for this is subsequently low.
* In attempt to anticipate possible issues, I checked that the timeout command is in the same path (/usr/bin) as the host command that is already called without a path, and the coreutils package (which contains timeout) is an Essential package. I also checked that timeout is not a built-in in bash, for those that have changed /bin/sh to bash (just in case).
[Original Bug Description]
On 18.04 Openconnect connects successfully to any of multiple VPN
concentrators but network traffic does not flow across the VPN tunnel
connection. When testing on 16.04 this works flawlessly. This also
worked on this system when it was on 17.10.
I have tried reducing the mtu of the tun0 network device but this has
not resulted in me being able to successfully ping the IP address.
Example showing ping attempt to the IP of DNS server:
~$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.
liam at liam-lat:~$ netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 wlp2s0
220.127.116.11 192.168.1.1 255.255.255.255 UGH 0 0 0 wlp2s0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
172.29.0.0 0.0.0.0 255.255.0.0 U 0 0 0 tun0
172.29.88.11 0.0.0.0 255.255.255.255 UH 0 0 0 tun0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 wlp2s0
liam at liam-lat:~$ ping 172.29.88.11
PING 172.29.88.11 (172.29.88.11) 56(84) bytes of data.
--- 172.29.88.11 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3054ms
DistroRelease: Ubuntu 18.04
Package: openconnect 7.08-3
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
Date: Wed Feb 28 22:11:33 2018
InstallationDate: Installed on 2017-06-15 (258 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
UpgradeStatus: Upgraded to bionic on 2018-02-22 (6 days ago)
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