Alpine 3.13 based images have no network access

[jokay]

Describe the Bug

Using the Alpine 3.13 based images, the network access does not to work.

When using the Alpine 3.12 based images, everything works.

Steps to Reproduce

Create a container using mcr.microsoft.com/dotnet/sdk:3.1.407-alpine3.13.

Restore a project having NuGet dependencies.

Results in the following error:

Determining projects to restore...
/usr/share/dotnet/sdk/3.1.407/NuGet.targets(128,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. [/app/demo.csproj]
/usr/share/dotnet/sdk/3.1.407/NuGet.targets(128,5): error :   Name does not resolve [/app/demo.csproj]

or for mcr.microsoft.com/dotnet/aspnet:3.1.13-alpine3.13 when accessing some external resource:

 ---> Running in 991c3f4e552d
fetch http://dl-3.alpinelinux.org/alpine/edge/testing/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/main/x86_64/APKINDEX.tar.gz
WARNING: Ignoring http://dl-3.alpinelinux.org/alpine/edge/testing: DNS lookup error
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/community/x86_64/APKINDEX.tar.gz

Output of docker version

Docker version 20.10.5, build 55c4c88

Output of docker info

Client:
 Context:    default
 Debug Mode: false

Server:
 Containers: 6
  Running: 0
  Paused: 0
  Stopped: 6
 Images: 75
 Server Version: 20.10.5
 Storage Driver: overlay2
  Backing Filesystem: btrfs
  Supports d_type: true
  Native Overlay Diff: false
 Logging Driver: json-file
 Cgroup Driver: none
 Cgroup Version: 1
 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: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 269548fa27e0089a8b8278fc4fc781d7f65a939b
 runc version: 12644e614e25b05da6fd08a38ffa0cfe1903fdec
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
  rootless
 Kernel Version: 5.10.0-0.bpo.3-amd64
 Operating System: Debian GNU/Linux 10 (buster)
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 15.52GiB
 Name: ***
 ID: ***
 Docker Root Dir: /home/system/.local/share/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Registry Mirrors:
 Live Restore Enabled: true
 Product License: Community Engine
 Default Address Pools:
   Base: 172.17.0.0/12, Size: 16
   Base: 10.0.0.0/8, Size: 24

[mthalman]

Have you verified that you have network connectivity just using the alpine:3.13 base image?

❯ docker pull alpine:3.13
3.13: Pulling from library/alpine
Digest: sha256:a75afd8b57e7f34e4dad8d65e2c7ba2e1975c795ce1ee22fa34f8cf46f96a3be
Status: Image is up to date for alpine:3.13
docker.io/library/alpine:3.13

❯ docker run --rm alpine:3.13 wget https://api.nuget.org/v3/index.json
Connecting to api.nuget.org (152.199.4.184:443)
saving to 'index.json'
index.json           100% |*****************************************************************************************************************************************************************|  8543  0:00:00 ETA
'index.json' saved

[jokay]

Good point.. really strange 🧐

Alpine 3.13

user@host:~$ docker pull alpine:3.13
3.13: Pulling from library/alpine
ba3557a56b15: Already exists 
Digest: sha256:a75afd8b57e7f34e4dad8d65e2c7ba2e1975c795ce1ee22fa34f8cf46f96a3be
Status: Downloaded newer image for alpine:3.13
docker.io/library/alpine:3.13

user@host:~$ docker run --rm alpine:3.13 wget https://api.nuget.org/v3/index.json
wget: bad address 'api.nuget.org'

Alpine 3.12

user@host:~$ docker pull alpine:3.12
3.12: Pulling from library/alpine
f84cab65f19f: Already exists 
Digest: sha256:a295107679b0d92cb70145fc18fb53c76e79fceed7e1cf10ed763c7c102c5ebe
Status: Downloaded newer image for alpine:3.12
docker.io/library/alpine:3.12

user@host:~$ docker run --rm alpine:3.12 wget https://api.nuget.org/v3/index.json
Connecting to api.nuget.org (152.199.23.209:443)
saving to 'index.json'
index.json           100% |********************************|  8543  0:00:00 ETA
'index.json' saved

[jokay]

Not related to the dotnet images, issue closed.

[jokay]

Relates alpinelinux/docker-alpine#155.