[systemd-devel] systemd-networkd: Failure to add slave interface to bridge

Tue Jan 31 12:11:45 UTC 2023

tun interfaces cannot be put in a bridge because they do not use an
Ethernet-like L2 link-layer header (or any L2 header at all, really;
they're purely L3 interfaces).

You need to use a 'tap' interface instead.

On Tue, Jan 31, 2023 at 1:05 PM Thomas Köller <thomas at koeller.dyndns.org>
wrote:

> I am trying to build a VPN tunnel through a tun interface created by
> sshd. The tun interface is to be added to an existing bridge interface.
> For this purpose I created a .network file (see below). However, the
> operation fails, without systemd-networkd giving a useful error message
> beyond 'Invalid argument', not even if logging is set do debug:
>
>
> Jan 31 11:04:59 sarkovy systemd-networkd[1294]: Setting log level to debug.
> Jan 31 11:04:59 sarkovy systemd-networkd[1294]: Sent message
> type=method_return sender=n/a destination=:1.213 path=n/a interface=n/a
> member=n/a cookie=44 reply_cookie=3 signature=n/a error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Saved new link:
> ifindex=6, iftype=NONE(65534), kind=tun
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Saved original MTU
> 1500 (min: 68, max: 65535)
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Saved IPv6
> link-local address generation mode: eui64
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Flags change:
> +MULTICAST +POINTOPOINT +NOARP
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=45 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: link pending udev
> initialization...
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: udev initialized link
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: State changed:
> pending -> initialized
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=46 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Found driver: tun
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Link state is
> up-to-date
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Unmanaging interface.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: State changed:
> initialized -> unmanaged
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=47 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: tun0: Interface name
> change detected, renamed to vpn_rpi400.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: udev
> initialized link
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: State
> changed: unmanaged -> initialized
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=48 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Link state
> is up-to-date
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: found
> matching network '/etc/systemd/network/50-vpn.network'.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Configuring
> with /etc/systemd/network/50-vpn.network.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: State
> changed: initialized -> configuring
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=49 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link is not activated.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link is not activated.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Setting
> '/proc/sys/net/ipv6/conf/vpn_rpi400/use_tempaddr' to '0'
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Setting
> '/proc/sys/net/ipv6/conf/vpn_rpi400/accept_ra' to '0'
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Setting
> '/proc/sys/net/ipv6/conf/vpn_rpi400/proxy_ndp' to '0'
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: No change in value '0',
> suppressing write
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Setting
> '/proc/sys/net/ipv4/conf/vpn_rpi400/promote_secondaries' to '1'
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: No change in value '1',
> suppressing write
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Requested to
> set link flags
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Requested to
> set IPv6LL address generation mode
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Requested to
> set master interface
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Requested to
> set bridge configurations
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Requested to
> activate link
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400:
> link_check_ready(): link layer is configuring.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Setting link
> flags
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Setting
> IPv6LL address generation mode
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Setting
> master interface
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: link flags set.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: IPv6LL
> address generation mode set.
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Failed to
> set master interface: Invalid argument
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: Failed
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: vpn_rpi400: State
> changed: configuring -> failed
> Jan 31 11:05:12 sarkovy systemd-networkd[1294]: Sent message type=signal
> sender=n/a destination=n/a path=/org/freedesktop/network1/link/_36
> interface=org.freedesktop.DBus.Properties member=PropertiesChanged
> cookie=50 reply_cookie=0 signature=sa{sv}as error-name=n/a
> error-message=n/a
> Jan 31 11:05:26 sarkovy systemd-networkd[1294]: Got message
> type=method_call sender=:1.215 destination=org.freedesktop.network1
> path=/org/freedesktop/network1 interface=org.freedesktop.DBus.Properties
> member=Get cookie=2 reply_cookie=0 signature=ss error-name=n/a
> error-message=n/a
> Jan 31 11:05:26 sarkovy systemd-networkd[1294]: Sent message
> type=method_return sender=n/a destination=:1.215 path=n/a interface=n/a
> member=n/a cookie=51 reply_cookie=2 signature=v error-name=n/a
> error-message=n/a
> Jan 31 11:06:35 sarkovy systemd-networkd[1294]: Got message
> type=method_call sender=:1.216 destination=org.freedesktop.network1
> path=/org/freedesktop/LogControl1
> interface=org.freedesktop.DBus.Properties member=Set cookie=3
> reply_cookie=0 signature=ssv error-name=n/a error-message=n/a
> Jan 31 11:06:35 sarkovy systemd-networkd[1294]: Sent message
> type=method_call sender=n/a destination=org.freedesktop.DBus
> path=/org/freedesktop/DBus interface=org.freedesktop.DBus
> member=GetConnectionUnixUser cookie=52 reply_cookie=0 signature=s
> error-name=n/a error-message=n/a
> Jan 31 11:06:35 sarkovy systemd-networkd[1294]: Got message
> type=method_return sender=org.freedesktop.DBus destination=:1.12
> path=n/a interface=n/a member=n/a cookie=4294967295 reply_cookie=52
> signature=u error-name=n/a error-message=n/a
>
>
> These are the contents of /etc/systemd/network/50-vpn.network:
>
> [Match]
> Name = vpn_*
>
> [Link]
> RequiredForOnline = no
> ActivationPolicy = up
> ARP = no
>
> [Network]
> Description = VPN interface
> DHCP = no
> DHCPServer = no
> LinkLocalAddressing = no
> DefaultRouteOnDevice = no
> LLMNR = no
> IPv6AcceptRA = no
> Bridge = br_lan
>
>

-- 
Mantas Mikulėnas
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