Merge pull request #185 from Jip-Hop/veth-extra

Veth extra

docs/network.md

@@ -42,6 +42,28 @@ systemctl status systemd-networkd
 ifconfig
 ```
 
+### Multiple Bridge Interfaces
+[Systemd-nspawn](https://www.freedesktop.org/software/systemd/man/latest/systemd-nspawn.html), the technology on which jailmaker is built, [currently](https://github.com/systemd/systemd/issues/11087) only supports the definition and automatic configuration of a single bridge interface via the [`--network-bridge`](https://www.freedesktop.org/software/systemd/man/latest/systemd-nspawn.html#--network-bridge=) argument.  In some cases however, for instance when trying to utilize different vlan interfaces, it can be useful to configure multiple bridge interfaces within a jail.  It is possible to create extra interfaces and join them to host bridges manually with systemd-nspwan using a combination of the [`--network-veth-extra`](https://www.freedesktop.org/software/systemd/man/latest/systemd-nspawn.html#--network-veth-extra=) argument and a service config containing `ExecStartPost` commands as outlined [here](https://wiki.csclub.uwaterloo.ca/Systemd-nspawn#Multiple_network_interfaces).
+
+The `--network-veth-extra` argument instructs system-nspawn to create an addition linked interface between the host and jail and uses a syntax of
+```
+--network-veth-extra=<host_interface_name>:<jail_interface_name>
+```
+
+The service config constaining `ExecStartPost` commands is then used to add the host side of the interface link to an existing host bridge and bring the interface up.  Jailmaker has simplified this process by including a `post_start_hook` configuration parameter which can automate the creation of the service config by including the `ExecStartPost` commands as below.
+
+```
+post_start_hook=#!/usr/bin/bash
+    set -euo pipefail
+    echo 'POST_START_HOOK'
+    ip link set dev ve-docker-1 master br40
+    ip link set dev ve-docker-1 up
+    ip link set dev ve-docker-2 master br70
+    ip link set dev ve-docker-2 up
+```
+
+With the new `--network-veth-extra` interface link created and the host side added to an existing host bridge, the jail side of the link still needs to be configured.  Jailmaker provides a network file in the form of `/etc/systemd/network/vee-dhcp.network` which will automatically perform this configuration.  In order for `vee-dhcp.network` to successfully match and configure the link's jail side interface, the `<jail_interface_name>` must begin with a ***vee-*** prefix.  An example jailmaker config with properly named `--network-veth-extra` interfaces and `post_start_hook` commands is available [here](https://github.com/Jip-Hop/jailmaker/discussions/179#discussioncomment-9499289).
+
 ## Macvlan Networking
 
 Some services require the use of port 80 or 443, or would benefit from a separate IP. For these situations the easiest network configuration is the MAC VLAN configuration. This creates a virtual interface with its own separate randomly generated MAC address and IP. The default config uses DHCP by default, but can easily be set to a Static IP.
@@ -91,4 +113,4 @@ apt update && apt -y install resolvconf
 
 - [systemd-nspawn](https://manpages.debian.org/bullseye/systemd-container/systemd-nspawn.1.en.html)- [Setting up Systemd-nspawn](https://www.cocode.se/linux/systemd_nspawn.html#orge360318)
 - [Debian Reference - Chapter 5. Network setup](https://www.debian.org/doc/manuals/debian-reference/ch05.en.html#_the_hostname_resolution)
-- [Disabling link-local addressing](https://jerrington.me/posts/2017-08-06-systemd-nspawn-disabling-link-local-addressing.html#disabling-link-local-addressing)
+- [Disabling link-local addressing](https://jerrington.me/posts/2017-08-06-systemd-nspawn-disabling-link-local-addressing.html#disabling-link-local-addressing)

jlmkr.py

@@ -4,7 +4,7 @@
 with full access to all files via bind mounts, \
 thanks to systemd-nspawn!"""
 
-__version__ = "1.4.2"
+__version__ = "1.5.0"
 __author__ = "Jip-Hop"
 __disclaimer__ = """USE THIS SCRIPT AT YOUR OWN RISK!
 IT COMES WITHOUT WARRANTY AND IS NOT SUPPORTED BY IXSYSTEMS."""
@@ -63,6 +63,16 @@ pre_start_hook=
 #     echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables
 #     echo 1 > /proc/sys/net/bridge/bridge-nf-call-ip6tables
 
+# Specify command/script to run on the HOST after starting the jail
+# For example to attach to multiple bridge interfaces 
+# when using --network-veth-extra=ve-myjail-1:veth1
+post_start_hook=
+# post_start_hook=#!/usr/bin/bash
+#     set -euo pipefail
+#     echo 'POST_START_HOOK_EXAMPLE'
+#     ip link set dev ve-myjail-1 master br2
+#     ip link set dev ve-myjail-1 up
+
 # Specify a command/script to run on the HOST after stopping the jail
 post_stop_hook=
 # post_stop_hook=echo 'POST_STOP_HOOK_EXAMPLE'
@@ -633,7 +643,7 @@ def start_jail(jail_name):
             "--capability=all",
         ]
 
-    # Add hooks to execute commands on the host before starting and after stopping a jail
+    # Add hooks to execute commands on the host before/after starting and after stopping a jail
     add_hook(
         jail_path,
         systemd_run_additional_args,
@@ -641,6 +651,13 @@ def start_jail(jail_name):
         "ExecStartPre",
     )
 
+    add_hook(
+        jail_path,
+        systemd_run_additional_args,
+        config.my_get("post_start_hook"),
+        "ExecStartPost",
+    )
+
     add_hook(
         jail_path,
         systemd_run_additional_args,
@@ -1499,6 +1516,28 @@ def create_jail(**kwargs):
                 file=open(os.path.join(network_dir_path, "mv-dhcp.network"), "w"),
             )
 
+            # Setup DHCP for veth-extra network interfaces
+            # This config applies when using the --network-veth-extra option of systemd-nspawn
+            # https://www.debian.org/doc/manuals/debian-reference/ch05.en.html#_the_modern_network_configuration_without_gui
+            print(
+                cleandoc(
+                    """
+                [Match]
+                Virtualization=container
+                Name=vee-*
+
+                [Network]
+                DHCP=yes
+                LinkLocalAddressing=ipv6
+
+                [DHCPv4]
+                UseDNS=true
+                UseTimezone=true
+            """
+                ),
+                file=open(os.path.join(network_dir_path, "vee-dhcp.network"), "w"),
+            )
+
             # Override preset which caused systemd-networkd to be disabled (e.g. fedora 39)
             # https://www.freedesktop.org/software/systemd/man/latest/systemd.preset.html
             # https://github.com/lxc/lxc-ci/blob/f632823ecd9b258ed42df40449ec54ed7ef8e77d/images/fedora.yaml#L312C5-L312C38