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engine/security/rootless: update for Docker Engine v29.5 #24645

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71 changes: 54 additions & 17 deletions content/manuals/engine/security/rootless/troubleshoot.md
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Original file line number Diff line number Diff line change
Expand Up @@ -77,10 +77,15 @@ weight: 30
- Exposing SCTP ports
- To use the `ping` command, see [Routing ping packets](./tips.md#routing-ping-packets).
- To expose privileged TCP/UDP ports (< 1024), see [Exposing privileged ports](./tips.md#exposing-privileged-ports).
- NFS mounts as the docker "data-root" is not supported. This limitation is not specific to rootless mode.

### Historical limitations

#### Until Docker Engine v29.5

- `IPAddress` shown in `docker inspect` is namespaced inside RootlessKit's network namespace.
This means the IP address is not reachable from the host without `nsenter`-ing into the network namespace.
- Host network (`docker run --net=host`) is also namespaced inside RootlessKit.
- NFS mounts as the docker "data-root" is not supported. This limitation is not specific to rootless mode.

## Troubleshooting

Expand Down Expand Up @@ -223,14 +228,18 @@ of network and port driver you use. If you're experiencing unexpected behavior
or performance related to networking, review the following table which shows
the configurations supported by RootlessKit, and how they compare:

| Network driver | Port driver | Net throughput | Port throughput | Source IP propagation | No SUID | Note |
| -------------- | -------------- | -------------- | --------------- | --------------------- | ------- | ---------------------------------------------------------------------------- |
| `slirp4netns` | `builtin` | Slow | Fast ✅ | ❌ | ✅ | Default in a typical setup |
| `vpnkit` | `builtin` | Slow | Fast ✅ | ❌ | ✅ | Default when `slirp4netns` isn't installed |
| `slirp4netns` | `slirp4netns` | Slow | Slow | ✅ | ✅ | |
| `pasta` | `implicit` | Slow | Fast ✅ | ✅ | ✅ | Experimental; Needs pasta version 2023_12_04 or later |
| `lxc-user-nic` | `builtin` | Fast ✅ | Fast ✅ | ❌ | ❌ | Experimental |
| `bypass4netns` | `bypass4netns` | Fast ✅ | Fast ✅ | ✅ | ✅ | **Note:** Not integrated to RootlessKit as it needs a custom seccomp profile |
| Network driver | Port driver | Net throughput | Port throughput | Source IP propagation | No SUID | Note |
| -------------- | -------------------- | -------------- | --------------- | --------------------- | ------- | ---------------------------------------------------------------------------- |
| `gvisor-tap-vsock`| `builtin` | Slow | Fast ✅ | ✅ (*) | ✅ | Default when slirp4netns is not installed |
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@thaJeztah thaJeztah Apr 25, 2026

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Micro-nit; can you align the header-width with the columns (or is it GitHub's rendering showing it wrong?)

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@AkihiroSuda AkihiroSuda Apr 25, 2026

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It seems aligned well, on macOS Terminal

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@thaJeztah thaJeztah Apr 25, 2026

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Ah, thx for checking; GitHub isn't great at rendering these 🤗

| `slirp4netns` | `builtin` | Slow | Fast ✅ | ✅ (*) | ✅ | Default when slirp4netns is installed |
| `vpnkit` | `builtin` | Slow | Fast ✅ | ✅ (*) | ✅ | Legacy |
| `gvisor-tap-vsock`| `gvisor-tap-vsock`| Slow | Slow | ❌ | ✅ | Not recommended. Use `builtin` port driver instead. |
| `slirp4netns` | `slirp4netns` | Slow | Slow | ✅ | ✅ | |
| `pasta` | `implicit` | Slow | Fast ✅ | ✅ | ✅ | Experimental; Needs pasta version 2023_12_04 or later |
| `lxc-user-nic` | `builtin` | Fast ✅ | Fast ✅ | ✅ (*) | ❌ | Experimental |
| `bypass4netns` | `bypass4netns` | Fast ✅ | Fast ✅ | ✅ | ✅ | **Note:** Not integrated to RootlessKit as it needs a custom seccomp profile |

(*) Applicable since RootlessKit v3.0. Also requires `userland-proxy` to be disabled.

For information about troubleshooting specific networking issues, see:

Expand Down Expand Up @@ -271,13 +280,13 @@ For details, see [Routing ping packets](./tips.md#routing-ping-packets).

#### `IPAddress` shown in `docker inspect` is unreachable

This is an expected behavior, as the daemon is namespaced inside RootlessKit's
network namespace. Use `docker run -p` instead.
This was an expected behavior until Docker Engine v29.5, as the daemon was namespaced inside RootlessKit's
network namespace. Use `docker run -p` instead, or upgrade to Docker Engine v29.5 or later.

#### `--net=host` doesn't listen ports on the host network namespace

This is an expected behavior, as the daemon is namespaced inside RootlessKit's
network namespace. Use `docker run -p` instead.
This was an expected behavior until Docker Engine v29.5, as the daemon was namespaced inside RootlessKit's
network namespace. Use `docker run -p` instead, or upgrade to Docker Engine v29.5 or later.

#### Network is slow

Expand All @@ -304,8 +313,34 @@ $ systemctl --user restart docker

#### `docker run -p` does not propagate source IP addresses

This is because Docker in rootless mode uses RootlessKit's `builtin` port
driver by default, which doesn't support source IP propagation. To enable
{{< tabs >}}
{{< tab name="RootlessKit v3.0 or later" >}}
This is because Docker Engine's `userland-proxy` is incompatible with RootlessKit's source IP propagation.

To disable userland-proxy, add the following configuration to `~/.config/docker/daemon.json`:
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@thaJeztah thaJeztah Apr 25, 2026

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@AkihiroSuda Is there still any situation where the userland-proxy could / should be used when running with rootlesskit? Wondering if we should also make the daemon ignore the option and disable it (print an info / warning possibly)

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@AkihiroSuda AkihiroSuda Apr 25, 2026 •
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Is there still any situation where the userland-proxy could / should be used when running with rootlesskit?

userland-proxy has to be used when br_netfilter is not loaded.

It shouldn't be a hard requirement unless enable_icc=false is used, but the current implementation still treats it as a hard requirement:


```json
{"userland-proxy": false}
```

Then restart the daemon:

```bash
systemctl --user restart docker
```

You may also need to load `br_netfilter` kernel module:

```bash
sudo tee /etc/modules-load.d/docker.conf <<EOF >/dev/null
br_netfilter
EOF

sudo systemctl restart systemd-modules-load.service
```
{{< /tab >}}
{{< tab name="Prior versions" >}}
This is because RootlessKit's `builtin` port didn't support source IP propagation until v3.0. To enable
source IP propagation, you can:

- Use the `slirp4netns` RootlessKit port driver
Expand Down Expand Up @@ -342,11 +377,13 @@ To change the RootlessKit networking configuration:
$ systemctl --user daemon-reload
$ systemctl --user restart docker
```
{{< /tab >}}
{{< /tabs >}}

For more information about networking options for RootlessKit, see:

- [Network drivers](https://github.com/rootless-containers/rootlesskit/blob/v2.0.0/docs/network.md)
- [Port drivers](https://github.com/rootless-containers/rootlesskit/blob/v2.0.0/docs/port.md)
- [Network drivers](https://github.com/rootless-containers/rootlesskit/blob/v3.0.0/docs/network.md)
- [Port drivers](https://github.com/rootless-containers/rootlesskit/blob/v3.0.0/docs/port.md)

### Tips for debugging

Expand Down
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