nixos: nixos/doc/manual/administration/container-networking.xml to CommonMark

nixos/doc/manual/administration/container-networking.section.md

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+# Container Networking {#sec-container-networking}
+
+When you create a container using `nixos-container create`, it gets it
+own private IPv4 address in the range `10.233.0.0/16`. You can get the
+container's IPv4 address as follows:
+
+```ShellSession
+# nixos-container show-ip foo
+10.233.4.2
+
+$ ping -c1 10.233.4.2
+64 bytes from 10.233.4.2: icmp_seq=1 ttl=64 time=0.106 ms
+```
+
+Networking is implemented using a pair of virtual Ethernet devices. The
+network interface in the container is called `eth0`, while the matching
+interface in the host is called `ve-container-name` (e.g., `ve-foo`).
+The container has its own network namespace and the `CAP_NET_ADMIN`
+capability, so it can perform arbitrary network configuration such as
+setting up firewall rules, without affecting or having access to the
+host's network.
+
+By default, containers cannot talk to the outside network. If you want
+that, you should set up Network Address Translation (NAT) rules on the
+host to rewrite container traffic to use your external IP address. This
+can be accomplished using the following configuration on the host:
+
+```nix
+networking.nat.enable = true;
+networking.nat.internalInterfaces = ["ve-+"];
+networking.nat.externalInterface = "eth0";
+```
+
+where `eth0` should be replaced with the desired external interface.
+Note that `ve-+` is a wildcard that matches all container interfaces.
+
+If you are using Network Manager, you need to explicitly prevent it from
+managing container interfaces:
+
+```nix
+networking.networkmanager.unmanaged = [ "interface-name:ve-*" ];
+```
+
+You may need to restart your system for the changes to take effect.