"Incorrect" host-gateway in case with Rootless Docker

[serhii-nakon]

Description

When use extra_hosts: "host.docker.internal:host-gateway" it use incorrect IP address to connect to host. host.docker.internal equal to 172.17.0.1 but should 10.0.2.2

Reproduce

1. Add to docker-compose.yaml

extra_hosts:
    - "host.docker.internal:host-gateway"

2. Run docker compose up
3. Run docker compose exec service_name curl -v http://host.docker.internal
4. Now you can see that it try to connect to incorrect IP

Expected behavior

host.docker.internal should be equal to 10.0.2.2

docker version

Client: Docker Engine - Community
 Version:           26.0.0
 API version:       1.45
 Go version:        go1.21.8
 Git commit:        2ae903e
 Built:             Wed Mar 20 15:18:01 2024
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          26.0.0
  API version:      1.45 (minimum version 1.24)
  Go version:       go1.21.8
  Git commit:       8b79278
  Built:            Wed Mar 20 15:18:01 2024
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.28
  GitCommit:        ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc:
  Version:          1.1.12
  GitCommit:        v1.1.12-0-g51d5e94
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
 rootlesskit:
  Version:          2.0.2
  ApiVersion:       1.1.1
  NetworkDriver:    slirp4netns
  PortDriver:       builtin
  StateDir:         /run/user/1000/dockerd-rootless
 slirp4netns:
  Version:          1.2.0
  GitCommit:        656041d45cfca7a4176f6b7eed9e4fe6c11e8383

docker info

Client: Docker Engine - Community
 Version:    26.0.0
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.13.1
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.25.0
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 22
  Running: 8
  Paused: 0
  Stopped: 14
 Images: 69
 Server Version: 26.0.0
 Storage Driver: overlay2
  Backing Filesystem: btrfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: false
  userxattr: true
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: runc io.containerd.runc.v2
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc version: v1.1.12-0-g51d5e94
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  rootless
  cgroupns
 Kernel Version: 6.8.4
 Operating System: Debian GNU/Linux 12 (bookworm)
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 30.76GiB
 Name: MSI-Bravo17
 ID: ff1c622b-6387-415e-8624-1fd851de327c
 Docker Root Dir: /home/serhy/.local/share/docker
 Debug Mode: false
 Username: nakonechnij.sergsj@gmail.com
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No cpuset support
WARNING: No io.weight support
WARNING: No io.weight (per device) support
WARNING: No io.max (rbps) support
WARNING: No io.max (wbps) support
WARNING: No io.max (riops) support
WARNING: No io.max (wiops) support
WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled

Additional Info

I know that I can use extra_hosts: "host.docker.internal:10.0.2.2" but I think that better way to not change code instead of hard code IPs.

[serhii-nakon]

If it possible, if user set env variable DOCKERD_ROOTLESS_ROOTLESSKIT_DISABLE_HOST_LOOPBACK=false change host-gateway to 10.0.2.2

[AkihiroSuda]

host.docker.internal should be equal to 10.0.2.2

It should be rather set to the host IP?

[serhii-nakon]

host.docker.internal should be equal to 10.0.2.2

It should be rather set to the host IP?

Hello @AkihiroSuda , yes.

[serhii-nakon]

@AkihiroSuda at least users will expect to connect to host like in case with non Rootless Docker. Most documentation and suggestion recommend to use extra host with host.docker.internal:host-gateway to connect to host