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 you to forward network connections between a host and an instance running on that host.

You can use them to:

• Forward traffic from an address on the host to an address inside the instance.

• Do the reverse, enabling an address inside the instance to connect through the host.

In NAT mode, proxy devices support TCP and UDP proxying (traffic forwarding). In non-NAT mode, proxy devices can also forward traffic between Unix sockets, which is useful for tasks such as forwarding a GUI or audio traffic from a container to the host system. Additionally, they can proxy traffic across different protocols—for example, forwarding traffic from a TCP listener on the host to a Unix socket inside a container.

The supported connection types are:

• tcp <-> tcp

• udp <-> udp

• unix <-> unix

• tcp <-> unix

• unix <-> tcp

• tcp <-> udp

• 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>

Tip

Using a proxy device in NAT mode is very similar to adding a network forward.

The difference is that network forwards are applied on a network level, while a proxy device is added for an instance. In addition, network forwards cannot be used to proxy traffic between different connection types.

NAT mode

The proxy device supports a NAT mode (nat=true), which forwards packets using NAT instead of creating a separate proxy connection.

This mode has the benefit that the client address is maintained without requiring the target destination to support the HAProxy PROXY protocol. This is necessary for passing client addresses in non-NAT mode.

However, NAT mode is only available when the host running the instance also acts as the gateway. This is the typical case when 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 square bracket notation. 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, which is 0.0.0.0 for IPv4 and [::] for IPv6.

Note

The listen address can also use wildcard addresses in 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:

bind

Which side to bind on

Key:	bind
Type:	string
Default:	host
Required:	no

Possible values are host and instance.

connect

Address and port to connect to

Key:	connect
Type:	string
Required:	yes

Use the following format to specify the address and port: <type>:<addr>:<port>[-<port>][,<port>]

gid

GID of the owner of the listening Unix socket

Key:	gid
Type:	integer
Default:	0
Required:	no

listen

Address and port to bind and listen

Key:	listen
Type:	string
Required:	yes

Use the following format to specify the address and port: <type>:<addr>:<port>[-<port>][,<port>]

mode

Mode for the listening Unix socket

Key:	mode
Type:	integer
Default:	0644
Required:	no

nat

Whether to optimize proxying via NAT

Key:	nat
Type:	bool
Default:	false
Required:	no

This option requires that the instance NIC has a static IP address.

proxy_protocol

Whether to use the HAProxy PROXY protocol

Key:	proxy_protocol
Type:	bool
Default:	false
Required:	no

This option specifies whether to use the HAProxy PROXY protocol to transmit sender information.

security.gid

What GID to drop privilege to

Key:	security.gid
Type:	integer
Default:	0
Required:	no

security.uid

What UID to drop privilege to

Key:	security.uid
Type:	integer
Default:	0
Required:	no

uid

UID of the owner of the listening Unix socket

Key:	uid
Type:	integer
Default:	0
Required:	no

Configuration examples

Add a proxy device that forwards traffic from one address (the listen address) to another address (the connect address) using NAT mode:

lxc config device add <instance_name> <device_name> proxy nat=true listen=tcp:<ip_address>:<port> connect=tcp:<ip_address>:<port>

Add a proxy device that forwards traffic going to a specific IP to a Unix socket on an instance that might not have a network connection:

lxc config device add <instance_name> <device_name> proxy listen=tcp:<ip_address>:<port> connect=unix:/<socket_path_on_instance>

Add a proxy device that forwards traffic going to a Unix socket on an instance that might not have a network connection to a specific IP address:

lxc config device add <instance_name> <device_name> proxy bind=instance listen=unix:/<socket_path_on_instance> connect=tcp:<ip_address>:<port>

See Configure devices for more information.