Secondary DNS servers are ignored, 8.8.8.8 is not being added #41041
Description
Description
The secondary DNS server passed via --dns option is being ignored, 8.8.8.8 is not being added as a backup server, contradictory to official documentation.
Steps to reproduce the issue:
Could reproduce on clean debian.
Ubuntu is affected just partially, if you specify both invalid DNS servers, it won't use 8.8.8.8.
Bridge is important, it works fine without it.
In this example 1.255 is not a valid DNS server, meanwhile 1.1 is.
$ docker network create -d bridge test
$ docker run --rm --dns 192.168.1.255 --dns 192.168.1.1 --network test --name test -it debian sh
# ping google.com
ping: google.com: Temporary failure in name resolution
$ docker run --rm --dns 192.168.1.1 --dns 192.168.1.255 --network test --name test -it debian sh
# ping google.com
PING google.com (108.177.14.113) 56(84) bytes of data.
64 bytes from lt-in-f113.1e100.net (108.177.14.113): icmp_seq=1 ttl=46 time=17.4 ms
Describe the results you received:
Secondary server is ignored, 8.8.8.8 is not being added.
Describe the results you expected:
Secondary server is not ignored, additional 8.8.8.8 added.
Additional information you deem important (e.g. issue happens only occasionally):
Output of docker version:
Client: Docker Engine - Community
Version: 19.03.9
API version: 1.40
Go version: go1.13.10
Git commit: 9d988398e7
Built: Fri May 15 00:25:25 2020
OS/Arch: linux/amd64
Experimental: false
Server: Docker Engine - Community
Engine:
Version: 19.03.9
API version: 1.40 (minimum version 1.12)
Go version: go1.13.10
Git commit: 9d988398e7
Built: Fri May 15 00:23:57 2020
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.2.13
GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc:
Version: 1.0.0-rc10
GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd
docker-init:
Version: 0.18.0
GitCommit: fec3683
Output of docker info:
Client:
Debug Mode: false
Server:
Containers: 0
Running: 0
Paused: 0
Stopped: 0
Images: 1
Server Version: 19.03.9
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc version: dc9208a3303feef5b3839f4323d9beb36df0a9dd
init version: fec3683
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 4.19.0-9-amd64
Operating System: Debian GNU/Linux 10 (buster)
OSType: linux
Architecture: x86_64
CPUs: 8
Total Memory: 11.64GiB
Name: debian-test
ID: VVRQ:CXMQ:N7CI:7LQI:M5AT:NYEC:HAUO:BTNK:3KWO:33TS:SS2U:MKMF
Docker Root Dir: /var/lib/docker
Debug Mode: false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
WARNING: No swap limit support
Additional environment details (AWS, VirtualBox, physical, etc.):
Linux debian-test 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2 (2020-04-29) x86_64 GNU/Linux
Couldn't get any significantly useful information from daemon debug logs, nothing related.