slirp4netns: actually make ipv6 default

We already have ipv6 enabled as default via the containers.conf setting.
However the documentation did not reflect this. Also if no options were
set in contianers.conf it would have ipv6 disabled.

We can now remove the extra option from containers.conf.

Also fix another outdated option description for host.containers.internal
and add that the options can also be set in contianers.conf.

[NO NEW TESTS NEEDED]

Fixes #13914

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

5 files changed, 13 insertions, 12 deletions

diff --git a/docs/source/markdown/podman-create.1.md b/docs/source/markdown/podman-create.1.md
index 45d0d0b3e..f6d028f4d 100644
--- a/docs/source/markdown/podman-create.1.md
+++ b/docs/source/markdown/podman-create.1.md
@@ -718,11 +718,11 @@ Valid _mode_ values are:
 - **host**: Do not create a network namespace, the container will use the host's network. Note: The host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
 - **ns:**_path_: Path to a network namespace to join.
 - **private**: Create a new namespace for the container. This will use the **bridge** mode for rootfull containers and **slirp4netns** for rootless ones.
-- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options:
-  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`, which is added to `/etc/hosts` as `host.containers.internal` for your convenience). Default is false.
+- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options, they can also be set with `network_cmd_options` in containers.conf:
+  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`). Default is false.
   - **mtu=MTU**: Specify the MTU to use for this network. (Default is `65520`).
   - **cidr=CIDR**: Specify ip range to use for this network. (Default is `10.0.2.0/24`).
-  - **enable_ipv6=true|false**: Enable IPv6. Default is false. (Required for `outbound_addr6`).
+  - **enable_ipv6=true|false**: Enable IPv6. Default is true. (Required for `outbound_addr6`).
   - **outbound_addr=INTERFACE**: Specify the outbound interface slirp should bind to (ipv4 traffic only).
   - **outbound_addr=IPv4**: Specify the outbound ipv4 address slirp should bind to.
   - **outbound_addr6=INTERFACE**: Specify the outbound interface slirp should bind to (ipv6 traffic only).
diff --git a/docs/source/markdown/podman-play-kube.1.md b/docs/source/markdown/podman-play-kube.1.md
index b959f6dd9..471c17f91 100644
--- a/docs/source/markdown/podman-play-kube.1.md
+++ b/docs/source/markdown/podman-play-kube.1.md
@@ -201,11 +201,11 @@ Valid _mode_ values are:
 - **container:**_id_: Reuse another container's network stack.
 - **ns:**_path_: Path to a network namespace to join.
 - **private**: Create a new namespace for the container. This will use the **bridge** mode for rootfull containers and **slirp4netns** for rootless ones.
-- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options:
-  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`, which is added to `/etc/hosts` as `host.containers.internal` for your convenience). Default is false.
+- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options, they can also be set with `network_cmd_options` in containers.conf:
+  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`). Default is false.
   - **mtu=MTU**: Specify the MTU to use for this network. (Default is `65520`).
   - **cidr=CIDR**: Specify ip range to use for this network. (Default is `10.0.2.0/24`).
-  - **enable_ipv6=true|false**: Enable IPv6. Default is false. (Required for `outbound_addr6`).
+  - **enable_ipv6=true|false**: Enable IPv6. Default is true. (Required for `outbound_addr6`).
   - **outbound_addr=INTERFACE**: Specify the outbound interface slirp should bind to (ipv4 traffic only).
   - **outbound_addr=IPv4**: Specify the outbound ipv4 address slirp should bind to.
   - **outbound_addr6=INTERFACE**: Specify the outbound interface slirp should bind to (ipv6 traffic only).
diff --git a/docs/source/markdown/podman-pod-create.1.md b/docs/source/markdown/podman-pod-create.1.md
index 2ae4453c9..1bf14efdb 100644
--- a/docs/source/markdown/podman-pod-create.1.md
+++ b/docs/source/markdown/podman-pod-create.1.md
@@ -166,11 +166,11 @@ Valid _mode_ values are:
 - **host**: Do not create a network namespace, the container will use the host's network. Note: The host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
 - **ns:**_path_: Path to a network namespace to join.
 - **private**: Create a new namespace for the container. This will use the **bridge** mode for rootfull containers and **slirp4netns** for rootless ones.
-- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options:
-  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`, which is added to `/etc/hosts` as `host.containers.internal` for your convenience). Default is false.
+- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options, they can also be set with `network_cmd_options` in containers.conf:
+  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`). Default is false.
   - **mtu=MTU**: Specify the MTU to use for this network. (Default is `65520`).
   - **cidr=CIDR**: Specify ip range to use for this network. (Default is `10.0.2.0/24`).
-  - **enable_ipv6=true|false**: Enable IPv6. Default is false. (Required for `outbound_addr6`).
+  - **enable_ipv6=true|false**: Enable IPv6. Default is true. (Required for `outbound_addr6`).
   - **outbound_addr=INTERFACE**: Specify the outbound interface slirp should bind to (ipv4 traffic only).
   - **outbound_addr=IPv4**: Specify the outbound ipv4 address slirp should bind to.
   - **outbound_addr6=INTERFACE**: Specify the outbound interface slirp should bind to (ipv6 traffic only).
diff --git a/docs/source/markdown/podman-run.1.md b/docs/source/markdown/podman-run.1.md
index 5c276c04a..8f72d4f49 100644
--- a/docs/source/markdown/podman-run.1.md
+++ b/docs/source/markdown/podman-run.1.md
@@ -742,11 +742,11 @@ Valid _mode_ values are:
 - **host**: Do not create a network namespace, the container will use the host's network. Note: The host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
 - **ns:**_path_: Path to a network namespace to join.
 - **private**: Create a new namespace for the container. This will use the **bridge** mode for rootfull containers and **slirp4netns** for rootless ones.
-- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options:
-  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`, which is added to `/etc/hosts` as `host.containers.internal` for your convenience). Default is false.
+- **slirp4netns[:OPTIONS,...]**: use **slirp4netns**(1) to create a user network stack. This is the default for rootless containers. It is possible to specify these additional options, they can also be set with `network_cmd_options` in containers.conf:
+  - **allow_host_loopback=true|false**: Allow the slirp4netns to reach the host loopback IP (`10.0.2.2`). Default is false.
   - **mtu=MTU**: Specify the MTU to use for this network. (Default is `65520`).
   - **cidr=CIDR**: Specify ip range to use for this network. (Default is `10.0.2.0/24`).
-  - **enable_ipv6=true|false**: Enable IPv6. Default is false. (Required for `outbound_addr6`).
+  - **enable_ipv6=true|false**: Enable IPv6. Default is true. (Required for `outbound_addr6`).
   - **outbound_addr=INTERFACE**: Specify the outbound interface slirp should bind to (ipv4 traffic only).
   - **outbound_addr=IPv4**: Specify the outbound ipv4 address slirp should bind to.
   - **outbound_addr6=INTERFACE**: Specify the outbound interface slirp should bind to (ipv6 traffic only).
diff --git a/libpod/networking_slirp4netns.go b/libpod/networking_slirp4netns.go
index 3f2842d4c..4a0ef0b3a 100644
--- a/libpod/networking_slirp4netns.go
+++ b/libpod/networking_slirp4netns.go
@@ -88,6 +88,7 @@ func parseSlirp4netnsNetworkOptions(r *Runtime, extraOptions []string) (*slirp4n
 		disableHostLoopback: true,
 		mtu:                 slirp4netnsMTU,
 		noPivotRoot:         r.config.Engine.NoPivotRoot,
+		enableIPv6:          true,
 	}
 	for _, o := range slirpOptions {
 		parts := strings.SplitN(o, "=", 2)