Type: proxy

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Note

The proxy device type is supported for both containers (NAT and non-NAT modes) and VMs (NAT mode only). It supports hotplugging for both containers and VMs.

Proxy devices allow forwarding network connections between host and instance. This method makes it possible to forward traffic hitting one of the host’s addresses to an address inside the instance, or to do the reverse and have an address in the instance connect through the host.

In NAT mode, a proxy device can be used for TCP and UDP proxying. In non-NAT mode, you can also proxy traffic between Unix sockets (which can be useful to, for example, forward graphical GUI or audio traffic from the container to the host system) or even across protocols (for example, you can have a TCP listener on the host system and forward its traffic to a Unix socket inside a container).

The supported connection types are:

• tcp <-> tcp

• udp <-> udp

• unix <-> unix

• tcp <-> unix

• unix <-> tcp

• udp <-> tcp

• tcp <-> udp

• udp <-> unix

• unix <-> udp

To add a proxy device, use the following command:

lxc config device add <instance_name> <device_name> proxy listen=<type>:<addr>:<port>[-<port>][,<port>] connect=<type>:<addr>:<port> bind=<host/instance_name>

NAT mode

The proxy device also supports a NAT mode (nat=true), where packets are forwarded using NAT rather than being proxied through a separate connection. This mode has the benefit that the client address is maintained without the need for the target destination to support the HAProxy PROXY protocol (which is the only way to pass the client address through when using the proxy device in non-NAT mode).

However, NAT mode is supported only if the host that the instance is running on is the gateway (which is the case if you’re using lxdbr0, for example).

In NAT mode, the supported connection types are:

• tcp <-> tcp

• udp <-> udp

When configuring a proxy device with nat=true, you must ensure that the target instance has a static IP configured on its NIC device.

Specifying IP addresses

Use the following command to configure a static IP for an instance NIC:

lxc config device set <instance_name> <nic_name> ipv4.address=<ipv4_address> ipv6.address=<ipv6_address>

To define a static IPv6 address, the parent managed network must have ipv6.dhcp.stateful enabled.

When defining IPv6 addresses, use the square bracket notation, for example:

connect=tcp:[2001:db8::1]:80

You can specify that the connect address should be the IP of the instance by setting the connect IP to the wildcard address (0.0.0.0 for IPv4 and [::] for IPv6).

Note

The listen address can also use wildcard addresses when using non-NAT mode. However, when using NAT mode, you must specify an IP address on the LXD host.

Device options

proxy devices have the following device options:

Key	Type	Default	Required	Description
bind	string	host	no	Which side to bind on (host/instance)
connect	string	-	yes	The address and port to connect to (<type>:<addr>:<port>[-<port>][,<port>])
gid	int	0	no	GID of the owner of the listening Unix socket
listen	string	-	yes	The address and port to bind and listen (<type>:<addr>:<port>[-<port>][,<port>])
mode	int	0644	no	Mode for the listening Unix socket
nat	bool	false	no	Whether to optimize proxying via NAT (requires that the instance NIC has a static IP address)
proxy_protocol	bool	false	no	Whether to use the HAProxy PROXY protocol to transmit sender information
security.gid	int	0	no	What GID to drop privilege to
security.uid	int	0	no	What UID to drop privilege to
uid	int	0	no	UID of the owner of the listening Unix socket