Public bug reported:
When using our company VPN, the Network Manager configured dnsmasq
ends up in a weird state where its unable to answer queries because
it's (incorrectly) sending them to 127.0.0.1:53 where nothing is
listening.
| root@ornery:~# nmcli con show 'Canonical UK - All Traffic' | grep -i dns
| ipv4.dns:
| ipv4.dns-search:
| ipv4.dns-options: (default)
| ipv4.ignore-auto-dns: no
| ipv6.dns:
| ipv6.dns-search:
| ipv6.dns-options: (default)
| ipv6.ignore-auto-dns: no
| IP4.DNS[1]: 10.172.192.1
| root@ornery:~# ps auxfwwwww | grep [4]035
| nobody 4035 0.0 0.0 52872 1620 ? S Jun29 6:39 \_
/usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces
--pid-file=/var/run/NetworkManager/dnsmasq.pid --listen-address=127.0.1.1
--cache-size=0 --proxy-dnssec
--enable-dbus=org.freedesktop.NetworkManager.dnsmasq
--conf-dir=/etc/NetworkManager/dnsmasq.d
| root@ornery:~#
Querying the DNS server provided by the VPN connection works; querying
dnsmasq doesn't:
| root@ornery:~# dig +short @10.172.192.1 www.openbsd.org
| 129.128.5.194
| root@ornery:~# dig @127.0.1.1 www.openbsd.org
|
| ; <<>> DiG 9.10.3-P4-Ubuntu <<>> @127.0.1.1 www.openbsd.org
| ; (1 server found)
| ;; global options: +cmd
| ;; Got answer:
| ;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 6996
| ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
|
| ;; QUESTION SECTION:
| ;www.openbsd.org. IN A
|
| ;; Query time: 0 msec
| ;; SERVER: 127.0.1.1#53(127.0.1.1)
| ;; WHEN: Mon Jul 18 10:25:48 CEST 2016
| ;; MSG SIZE rcvd: 33
|
| root@ornery:~#
While running 'dig @127.0.1.1 www.openbsd.org':
| root@ornery:~# tcpdump -i lo port 53 -v -n
| tcpdump: listening on lo, link-type EN10MB (Ethernet), capture size 262144
bytes
| 10:26:04.728905 IP (tos 0x0, ttl 64, id 56577, offset 0, flags [none], proto
UDP (17), length 72)
| 127.0.0.1.54917 > 127.0.1.1.53: 32273+ [1au] A? www.openbsd.org. (44)
| 10:26:04.729001 IP (tos 0x0, ttl 64, id 49204, offset 0, flags [DF], proto
UDP (17), length 61)
| 127.0.1.1.53 > 127.0.0.1.54917: 32273 Refused$ 0/0/0 (33)
| root@ornery:~# netstat -anp | grep 127.0.[01].1:53
| tcp 0 0 127.0.1.1:53 0.0.0.0:* LISTEN
4035/dnsmasq
| udp 0 0 127.0.1.1:53 0.0.0.0:*
4035/dnsmasq
| root@ornery:~#
You can see below a) that dnsmasq thinks it is configured to use a DNS
server provided by the VPN, and/but that b) it tries to answer a non
local query like www.openbsd.org locally.
| root@ornery:~# kill -USR1 4035; tail /var/log/syslog | grep dnsmasq
| Jul 18 09:29:22 ornery dnsmasq[4035]: time 1468830562
| Jul 18 09:29:22 ornery dnsmasq[4035]: cache size 0, 0/0 cache insertions
re-used unexpired cache entries.
| Jul 18 09:29:22 ornery dnsmasq[4035]: queries forwarded 1880976, queries
answered locally 375041
| Jul 18 09:29:22 ornery dnsmasq[4035]: queries for authoritative zones 0
| Jul 18 09:29:22 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent
792, retried or failed 0
| root@ornery:~# dig +short @127.0.1.1 www.openbsd.org
| root@ornery:~# kill -USR1 4035; tail /var/log/syslog | grep dnsmasq
| Jul 18 09:29:22 ornery dnsmasq[4035]: queries for authoritative zones 0
| Jul 18 09:29:22 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent
792, retried or failed 0
| Jul 18 09:29:37 ornery dnsmasq[4035]: time 1468830577
| Jul 18 09:29:37 ornery dnsmasq[4035]: cache size 0, 0/0 cache insertions
re-used unexpired cache entries.
| Jul 18 09:29:37 ornery dnsmasq[4035]: queries forwarded 1880976, queries
answered locally 375042
| Jul 18 09:29:37 ornery dnsmasq[4035]: queries for authoritative zones 0
| Jul 18 09:29:37 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent
792, retried or failed 0
| root@ornery:~#
This is on Ubuntu 16.04, with the following packages:
| james@ornery:~$ COLUMNS=200 dpkg -l dnsmasq-base network-manager
network-manager-openvpn | grep ^ii
| ii dnsmasq-base 2.75-1ubuntu0.16.04.1
amd64 Small caching DNS proxy and DHCP/TFTP server
| ii network-manager 1.2.0-0ubuntu0.16.04.2
amd64 network management framework (daemon and userspace
tools)
| ii network-manager-openvpn 1.1.93-1ubuntu1
amd64 network management framework (OpenVPN plugin core)
| james@ornery:~$
** Affects: network-manager (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1603898
Title:
DNS resolution fails when using VPN and routing all traffic over it
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