[PATCH net-next v3 04/11] netlink: specs: add specification for wireguard

Asbjørn Sloth Tønnesen
2025-11-05T18:33:03Z

This patch adds an near[1] complete YNL specification for wireguard,
documenting the protocol in a machine-readable format, than the
comment in wireguard.h, and eases usage from C and non-C programming
languages alike.

The generated C library will be featured in the next patch, so in
this patch I will use the in-kernel python client for examples.

This makes the documentation in the UAPI header redundant, and
it is therefore removed. The in-line documentation in the spec,
is based on the existing comment in wireguard.h, and once released
then it will be available in the kernel documentation at:
https://docs.kernel.org/netlink/specs/wireguard.html
(until then run: make htmldocs)

Generate wireguard.rst from this spec:
$ make -C tools/net/ynl/generated/ wireguard.rst

Query wireguard interface through pyynl:
$ sudo ./tools/net/ynl/pyynl/cli.py --family wireguard \
--dump get-device \
--json '{"ifindex":3}'
[{'fwmark': 0,
'ifindex': 3,
'ifname': 'wg-test',
'listen-port': 54318,
'peers': [{0: {'allowedips': [{0: {'cidr-mask': 0,
'family': 2,
'ipaddr': '0.0.0.0'}},
{0: {'cidr-mask': 0,
'family': 10,
'ipaddr': '::'}}],
'endpoint': b'[...]',
'last-handshake-time': {'nsec': 42, 'sec': 42},
'persistent-keepalive-interval': 42,
'preshared-key': '[...]',
'protocol-version': 1,
'public-key': '[...]',
'rx-bytes': 42,
'tx-bytes': 42}}],
'private-key': '[...]',
'public-key': '[...]'}]

Add another allowed IP prefix:
$ sudo ./tools/net/ynl/pyynl/cli.py --family wireguard \
--do set-device --json '{"ifindex":3,"peers":[
{"public-key":"6a df b1 83 a4 ..","allowedips":[
{"cidr-mask":0,"family":10,"ipaddr":"::"}]}]}'

[1] As can be seen above, the "endpoint" is only decoded as binary data,
as it can't be described fully in YNL. It's a struct sockaddr_in or
struct sockaddr_in6 depending on the attribute length.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
---
Documentation/netlink/specs/wireguard.yaml | 301 +++++++++++++++++++++
MAINTAINERS | 1 +
include/uapi/linux/wireguard.h | 129 ---------
3 files changed, 302 insertions(+), 129 deletions(-)
create mode 100644 Documentation/netlink/specs/wireguard.yaml

diff --git a/Documentation/netlink/specs/wireguard.yaml b/Documentation/netlink/specs/wireguard.yaml
new file mode 100644
index 000000000000..7dcb2dec3d06
--- /dev/null
+++ b/Documentation/netlink/specs/wireguard.yaml
@@ -0,0 +1,301 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+---
+name: wireguard
+protocol: genetlink-legacy
+
+doc: |
+ **Netlink protocol to control WireGuard network devices.**
+
+ The below enums and macros are for interfacing with WireGuard,
+ using generic netlink, with family ``WG_GENL_NAME`` and version
+ ``WG_GENL_VERSION``. It defines two commands: get and set.
+ Note that while they share many common attributes, these two
+ commands actually accept a slightly different set of inputs and
+ outputs. These differences are noted under the individual attributes.
+c-family-name: wg-genl-name
+c-version-name: wg-genl-version
+max-by-define: true
+
+definitions:
+ -
+ name-prefix: wg-
+ name: key-len
+ type: const
+ value: 32
+ -
+ name: --kernel-timespec
+ type: struct
+ header: linux/time_types.h
+ members:
+ -
+ name: sec
+ type: u64
+ doc: Number of seconds, since UNIX epoch.
+ -
+ name: nsec
+ type: u64
+ doc: Number of nanoseconds, after the second began.
+ -
+ name: wgdevice-flags
+ name-prefix: wgdevice-f-
+ enum-name: wgdevice-flag
+ type: flags
+ entries:
+ - replace-peers
+ -
+ name: wgpeer-flags
+ name-prefix: wgpeer-f-
+ enum-name: wgpeer-flag
+ type: flags
+ entries:
+ - remove-me
+ - replace-allowedips
+ - update-only
+ -
+ name: wgallowedip-flags
+ name-prefix: wgallowedip-f-
+ enum-name: wgallowedip-flag
+ type: flags
+ entries:
+ - remove-me
+
+attribute-sets:
+ -
+ name: wgdevice
+ enum-name: wgdevice-attribute
+ name-prefix: wgdevice-a-
+ attr-cnt-name: --wgdevice-a-last
+ attributes:
+ -
+ name: unspec
+ type: unused
+ value: 0
+ -
+ name: ifindex
+ type: u32
+ -
+ name: ifname
+ type: string
+ checks:
+ max-len: 15
+ -
+ name: private-key
+ type: binary
+ doc: Set to all zeros to remove.
+ display-hint: hex
+ checks:
+ exact-len: wg-key-len
+ -
+ name: public-key
+ type: binary
+ display-hint: hex
+ checks:
+ exact-len: wg-key-len
+ -
+ name: flags
+ type: u32
+ doc: |
+ ``0`` or ``WGDEVICE_F_REPLACE_PEERS`` if all current peers
+ should be removed prior to adding the list below.
+ enum: wgdevice-flags
+ -
+ name: listen-port
+ type: u16
+ doc: Set as ``0`` to choose randomly.
+ -
+ name: fwmark
+ type: u32
+ doc: Set as ``0`` to disable.
+ -
+ name: peers
+ type: indexed-array
+ sub-type: nest
+ nested-attributes: wgpeer
+ doc: The index is set as ``0`` in ``DUMP``, and unused in ``DO``.
+ -
+ name: wgpeer
+ enum-name: wgpeer-attribute
+ name-prefix: wgpeer-a-
+ attr-cnt-name: --wgpeer-a-last
+ attributes:
+ -
+ name: unspec
+ type: unused
+ value: 0
+ -
+ name: public-key
+ type: binary
+ display-hint: hex
+ checks:
+ exact-len: wg-key-len
+ -
+ name: preshared-key
+ type: binary
+ doc: Set as all zeros to remove.
+ display-hint: hex
+ checks:
+ exact-len: wg-key-len
+ -
+ name: flags
+ type: u32
+ doc: |
+ ``0`` and/or ``WGPEER_F_REMOVE_ME`` if the specified peer should not
+ exist at the end of the operation, rather than added/updated
+ and/or ``WGPEER_F_REPLACE_ALLOWEDIPS`` if all current allowed IPs
+ of this peer should be removed prior to adding the list below
+ and/or ``WGPEER_F_UPDATE_ONLY`` if the peer should only be set if
+ it already exists.
+ enum: wgpeer-flags
+ -
+ name: endpoint
+ type: binary
+ doc: struct sockaddr_in or struct sockaddr_in6
+ checks:
+ min-len: 16
+ -
+ name: persistent-keepalive-interval
+ type: u16
+ doc: Set as ``0`` to disable.
+ -
+ name: last-handshake-time
+ type: binary
+ struct: --kernel-timespec
+ checks:
+ exact-len: 16
+ -
+ name: rx-bytes
+ type: u64
+ -
+ name: tx-bytes
+ type: u64
+ -
+ name: allowedips
+ type: indexed-array
+ sub-type: nest
+ nested-attributes: wgallowedip
+ doc: The index is set as ``0`` in ``DUMP``, and unused in ``DO``.
+ -
+ name: protocol-version
+ type: u32
+ doc: |
+ Should not be set or used at all by most users of this API,
+ as the most recent protocol will be used when this is unset.
+ Otherwise, must be set to ``1``.
+ -
+ name: wgallowedip
+ enum-name: wgallowedip-attribute
+ name-prefix: wgallowedip-a-
+ attr-cnt-name: --wgallowedip-a-last
+ attributes:
+ -
+ name: unspec
+ type: unused
+ value: 0
+ -
+ name: family
+ type: u16
+ doc: IP family, either ``AF_INET`` or ``AF_INET6``.
+ -
+ name: ipaddr
+ type: binary
+ doc: Either ``struct in_addr`` or ``struct in6_addr``.
+ display-hint: ipv4-or-v6
+ checks:
+ min-len: 4
+ -
+ name: cidr-mask
+ type: u8
+ -
+ name: flags
+ type: u32
+ doc: |
+ ``WGALLOWEDIP_F_REMOVE_ME`` if the specified IP should be
+ removed; otherwise, this IP will be added if it is not
+ already present.
+ enum: wgallowedip-flags
+
+operations:
+ enum-name: wg-cmd
+ name-prefix: wg-cmd-
+ list:
+ -
+ name: get-device
+ value: 0
+ doc: |
+ Retrieve WireGuard device
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ The command should be called with one but not both of:
+
+ - ``WGDEVICE_A_IFINDEX``
+ - ``WGDEVICE_A_IFNAME``
+
+ The kernel will then return several messages (``NLM_F_MULTI``).
+ It is possible that all of the allowed IPs of a single peer
+ will not fit within a single netlink message. In that case, the
+ same peer will be written in the following message, except it will
+ only contain ``WGPEER_A_PUBLIC_KEY`` and ``WGPEER_A_ALLOWEDIPS``.
+ This may occur several times in a row for the same peer.
+ It is then up to the receiver to coalesce adjacent peers.
+ Likewise, it is possible that all peers will not fit within a
+ single message.
+ So, subsequent peers will be sent in following messages,
+ except those will only contain ``WGDEVICE_A_IFNAME`` and
+ ``WGDEVICE_A_PEERS``. It is then up to the receiver to coalesce
+ these messages to form the complete list of peers.
+
+ While this command does accept the other ``WGDEVICE_A_*``
+ attributes, for compatibility reasons, but they are ignored
+ by this command, and should not be used in requests.
+
+ Since this is an ``NLA_F_DUMP`` command, the final message will
+ always be ``NLMSG_DONE``, even if an error occurs. However, this
+ ``NLMSG_DONE`` message contains an integer error code. It is
+ either zero or a negative error code corresponding to the errno.
+ attribute-set: wgdevice
+ flags: [uns-admin-perm]
+
+ dump:
+ pre: wireguard-nl-get-device-start
+ post: wireguard-nl-get-device-done
+ # request only uses ifindex | ifname, but keep .maxattr as is
+ request: &all-attrs
+ attributes:
+ - ifindex
+ - ifname
+ - private-key
+ - public-key
+ - flags
+ - listen-port
+ - fwmark
+ - peers
+ reply: *all-attrs
+ -
+ name: set-device
+ value: 1
+ doc: |
+ Set WireGuard device
+ ~~~~~~~~~~~~~~~~~~~~
+
+ This command should be called with a wgdevice set, containing one
+ but not both of ``WGDEVICE_A_IFINDEX`` and ``WGDEVICE_A_IFNAME``.
+
+ It is possible that the amount of configuration data exceeds that
+ of the maximum message length accepted by the kernel.
+ In that case, several messages should be sent one after another,
+ with each successive one filling in information not contained in
+ the prior.
+ Note that if ``WGDEVICE_F_REPLACE_PEERS`` is specified in the first
+ message, it probably should not be specified in fragments that come
+ after, so that the list of peers is only cleared the first time but
+ appended after.
+ Likewise for peers, if ``WGPEER_F_REPLACE_ALLOWEDIPS`` is specified
+ in the first message of a peer, it likely should not be specified
+ in subsequent fragments.
+
+ If an error occurs, ``NLMSG_ERROR`` will reply containing an errno.
+ attribute-set: wgdevice
+ flags: [uns-admin-perm]
+
+ do:
+ request: *all-attrs
diff --git a/MAINTAINERS b/MAINTAINERS
index bdf0a3a0dd36..35cd289899f7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27649,6 +27649,7 @@ M: Jason A. Donenfeld <Jason@zx2c4.com>
L: wireguard@lists.zx2c4.com
L: netdev@vger.kernel.org
S: Maintained
+F: Documentation/netlink/specs/wireguard.yaml
F: drivers/net/wireguard/
F: tools/testing/selftests/wireguard/

diff --git a/include/uapi/linux/wireguard.h b/include/uapi/linux/wireguard.h
index 8c26391196d5..dee4401e0b5d 100644
--- a/include/uapi/linux/wireguard.h
+++ b/include/uapi/linux/wireguard.h
@@ -1,135 +1,6 @@
/* SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) OR MIT */
/*
* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
- *
- * Documentation
- * =============
- *
- * The below enums and macros are for interfacing with WireGuard, using generic
- * netlink, with family WG_GENL_NAME and version WG_GENL_VERSION. It defines two
- * methods: get and set. Note that while they share many common attributes,
- * these two functions actually accept a slightly different set of inputs and
- * outputs.
- *
- * WG_CMD_GET_DEVICE
- * -----------------
- *
- * May only be called via NLM_F_REQUEST | NLM_F_DUMP. The command should contain
- * one but not both of:
- *
- * WGDEVICE_A_IFINDEX: NLA_U32
- * WGDEVICE_A_IFNAME: NLA_NUL_STRING, maxlen IFNAMSIZ - 1
- *
- * The kernel will then return several messages (NLM_F_MULTI) containing the
- * following tree of nested items:
- *
- * WGDEVICE_A_IFINDEX: NLA_U32
- * WGDEVICE_A_IFNAME: NLA_NUL_STRING, maxlen IFNAMSIZ - 1
- * WGDEVICE_A_PRIVATE_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
- * WGDEVICE_A_PUBLIC_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
- * WGDEVICE_A_LISTEN_PORT: NLA_U16
- * WGDEVICE_A_FWMARK: NLA_U32
- * WGDEVICE_A_PEERS: NLA_NESTED
- * 0: NLA_NESTED
- * WGPEER_A_PUBLIC_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
- * WGPEER_A_PRESHARED_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
- * WGPEER_A_ENDPOINT: NLA_MIN_LEN(struct sockaddr), struct sockaddr_in or struct sockaddr_in6
- * WGPEER_A_PERSISTENT_KEEPALIVE_INTERVAL: NLA_U16
- * WGPEER_A_LAST_HANDSHAKE_TIME: NLA_EXACT_LEN, struct __kernel_timespec
- * WGPEER_A_RX_BYTES: NLA_U64
- * WGPEER_A_TX_BYTES: NLA_U64
- * WGPEER_A_ALLOWEDIPS: NLA_NESTED
- * 0: NLA_NESTED
- * WGALLOWEDIP_A_FAMILY: NLA_U16
- * WGALLOWEDIP_A_IPADDR: NLA_MIN_LEN(struct in_addr), struct in_addr or struct in6_addr
- * WGALLOWEDIP_A_CIDR_MASK: NLA_U8
- * 0: NLA_NESTED
- * ...
- * 0: NLA_NESTED
- * ...
- * ...
- * WGPEER_A_PROTOCOL_VERSION: NLA_U32
- * 0: NLA_NESTED
- * ...
- * ...
- *
- * It is possible that all of the allowed IPs of a single peer will not
- * fit within a single netlink message. In that case, the same peer will
- * be written in the following message, except it will only contain
- * WGPEER_A_PUBLIC_KEY and WGPEER_A_ALLOWEDIPS. This may occur several
- * times in a row for the same peer. It is then up to the receiver to
- * coalesce adjacent peers. Likewise, it is possible that all peers will
- * not fit within a single message. So, subsequent peers will be sent
- * in following messages, except those will only contain WGDEVICE_A_IFNAME
- * and WGDEVICE_A_PEERS. It is then up to the receiver to coalesce these
- * messages to form the complete list of peers.
- *
- * Since this is an NLA_F_DUMP command, the final message will always be
- * NLMSG_DONE, even if an error occurs. However, this NLMSG_DONE message
- * contains an integer error code. It is either zero or a negative error
- * code corresponding to the errno.
- *
- * WG_CMD_SET_DEVICE
- * -----------------
- *
- * May only be called via NLM_F_REQUEST. The command should contain the
- * following tree of nested items, containing one but not both of
- * WGDEVICE_A_IFINDEX and WGDEVICE_A_IFNAME:
- *
- * WGDEVICE_A_IFINDEX: NLA_U32
- * WGDEVICE_A_IFNAME: NLA_NUL_STRING, maxlen IFNAMSIZ - 1
- * WGDEVICE_A_FLAGS: NLA_U32, 0 or WGDEVICE_F_REPLACE_PEERS if all current
- * peers should be removed prior to adding the list below.
- * WGDEVICE_A_PRIVATE_KEY: len WG_KEY_LEN, all zeros to remove
- * WGDEVICE_A_LISTEN_PORT: NLA_U16, 0 to choose randomly
- * WGDEVICE_A_FWMARK: NLA_U32, 0 to disable
- * WGDEVICE_A_PEERS: NLA_NESTED
- * 0: NLA_NESTED
- * WGPEER_A_PUBLIC_KEY: len WG_KEY_LEN
- * WGPEER_A_FLAGS: NLA_U32, 0 and/or WGPEER_F_REMOVE_ME if the
- * specified peer should not exist at the end of the
- * operation, rather than added/updated and/or
- * WGPEER_F_REPLACE_ALLOWEDIPS if all current allowed
- * IPs of this peer should be removed prior to adding
- * the list below and/or WGPEER_F_UPDATE_ONLY if the
- * peer should only be set if it already exists.
- * WGPEER_A_PRESHARED_KEY: len WG_KEY_LEN, all zeros to remove
- * WGPEER_A_ENDPOINT: struct sockaddr_in or struct sockaddr_in6
- * WGPEER_A_PERSISTENT_KEEPALIVE_INTERVAL: NLA_U16, 0 to disable
- * WGPEER_A_ALLOWEDIPS: NLA_NESTED
- * 0: NLA_NESTED
- * WGALLOWEDIP_A_FAMILY: NLA_U16
- * WGALLOWEDIP_A_IPADDR: struct in_addr or struct in6_addr
- * WGALLOWEDIP_A_CIDR_MASK: NLA_U8
- * WGALLOWEDIP_A_FLAGS: NLA_U32, WGALLOWEDIP_F_REMOVE_ME if
- * the specified IP should be removed;
- * otherwise, this IP will be added if
- * it is not already present.
- * 0: NLA_NESTED
- * ...
- * 0: NLA_NESTED
- * ...
- * ...
- * WGPEER_A_PROTOCOL_VERSION: NLA_U32, should not be set or used at
- * all by most users of this API, as the
- * most recent protocol will be used when
- * this is unset. Otherwise, must be set
- * to 1.
- * 0: NLA_NESTED
- * ...
- * ...
- *
- * It is possible that the amount of configuration data exceeds that of
- * the maximum message length accepted by the kernel. In that case, several
- * messages should be sent one after another, with each successive one
- * filling in information not contained in the prior. Note that if
- * WGDEVICE_F_REPLACE_PEERS is specified in the first message, it probably
- * should not be specified in fragments that come after, so that the list
- * of peers is only cleared the first time but appended after. Likewise for
- * peers, if WGPEER_F_REPLACE_ALLOWEDIPS is specified in the first message
- * of a peer, it likely should not be specified in subsequent fragments.
- *
- * If an error occurs, NLMSG_ERROR will reply containing an errno.
*/

#ifndef _WG_UAPI_WIREGUARD_H
--
2.51.0