[PATCH net-next v18 03/25] ovpn: add basic interface creation/destruction/management routines

Antonio Quartulli
2025-01-13T09:31:08Z

Add basic infrastructure for handling ovpn interfaces.

Tested-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
Documentation/netlink/specs/rt_link.yaml | 16 +++++
drivers/net/ovpn/Makefile | 1 +
drivers/net/ovpn/io.c | 22 ++++++
drivers/net/ovpn/io.h | 24 +++++++
drivers/net/ovpn/main.c | 113 +++++++++++++++++++++++++++++--
drivers/net/ovpn/ovpnstruct.h | 7 ++
drivers/net/ovpn/proto.h | 38 +++++++++++
include/uapi/linux/if_link.h | 15 ++++
8 files changed, 231 insertions(+), 5 deletions(-)

diff --git a/Documentation/netlink/specs/rt_link.yaml b/Documentation/netlink/specs/rt_link.yaml
index 0d492500c7e57dcafcd4b81823abf1c3040c3e78..2cb4743c6cf6f095895dff5b7b23adac572d9386 100644
--- a/Documentation/netlink/specs/rt_link.yaml
+++ b/Documentation/netlink/specs/rt_link.yaml
@@ -926,6 +926,12 @@ definitions:
entries:
- name: none
- name: default
+ -
+ name: ovpn-mode
+ type: enum
+ entries:
+ - p2p
+ - mp

attribute-sets:
-
@@ -2253,6 +2259,13 @@ attribute-sets:
-
name: tailroom
type: u16
+ -
+ name: linkinfo-ovpn-attrs
+ attributes:
+ -
+ name: mode
+ type: u8
+ enum: ovpn-mode

sub-messages:
-
@@ -2303,6 +2316,9 @@ sub-messages:
-
value: netkit
attribute-set: linkinfo-netkit-attrs
+ -
+ value: ovpn
+ attribute-set: linkinfo-ovpn-attrs
-
name: linkinfo-member-data-msg
formats:
diff --git a/drivers/net/ovpn/Makefile b/drivers/net/ovpn/Makefile
index 19305a39e57eede2dc391aa0423702c5321649a6..201dc001419f1d99ae95c0ee0f96e68f8a4eac16 100644
--- a/drivers/net/ovpn/Makefile
+++ b/drivers/net/ovpn/Makefile
@@ -8,5 +8,6 @@

obj-$(CONFIG_OVPN) := ovpn.o
ovpn-y += main.o
+ovpn-y += io.o
ovpn-y += netlink.o
ovpn-y += netlink-gen.o
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
new file mode 100644
index 0000000000000000000000000000000000000000..ad3813419c33cbdfe7e8ad6f5c8b444a3540a69f
--- /dev/null
+++ b/drivers/net/ovpn/io.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+/* OpenVPN data channel offload
+ *
+ * Copyright (C) 2019-2024 OpenVPN, Inc.
+ *
+ * Author: James Yonan <james@openvpn.net>
+ * Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+
+#include "io.h"
+
+/* Send user data to the network
+ */
+netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+ skb_tx_error(skb);
+ kfree_skb(skb);
+ return NET_XMIT_DROP;
+}
diff --git a/drivers/net/ovpn/io.h b/drivers/net/ovpn/io.h
new file mode 100644
index 0000000000000000000000000000000000000000..a90537e9af6c0d2f38da229bdc2d8c639f2d11d1
--- /dev/null
+++ b/drivers/net/ovpn/io.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* OpenVPN data channel offload
+ *
+ * Copyright (C) 2019-2024 OpenVPN, Inc.
+ *
+ * Author: James Yonan <james@openvpn.net>
+ * Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#ifndef _NET_OVPN_OVPN_H_
+#define _NET_OVPN_OVPN_H_
+
+/* DATA_V2 header size with AEAD encryption */
+#define OVPN_HEAD_ROOM (OVPN_OPCODE_SIZE + OVPN_NONCE_WIRE_SIZE + \
+ 16 /* AEAD TAG length */ + \
+ max(sizeof(struct udphdr), sizeof(struct tcphdr)) +\
+ max(sizeof(struct ipv6hdr), sizeof(struct iphdr)))
+
+/* max padding required by encryption */
+#define OVPN_MAX_PADDING 16
+
+netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev);
+
+#endif /* _NET_OVPN_OVPN_H_ */
diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 3475dab4b40f3edd882e05dbdf8badd03d7c78a3..d3eebab7fa528cb648141021ab513c3ed687e698 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -10,14 +10,42 @@
#include <linux/genetlink.h>
#include <linux/module.h>
#include <linux/netdevice.h>
+#include <linux/inetdevice.h>
+#include <net/ip.h>
#include <net/rtnetlink.h>
-#include <uapi/linux/ovpn.h>
+#include <uapi/linux/if_arp.h>

#include "ovpnstruct.h"
#include "main.h"
#include "netlink.h"
+#include "io.h"
+#include "proto.h"
+
+static int ovpn_net_open(struct net_device *dev)
+{
+ netif_tx_start_all_queues(dev);
+ return 0;
+}
+
+static int ovpn_net_stop(struct net_device *dev)
+{
+ netif_tx_stop_all_queues(dev);
+ return 0;
+}

static const struct net_device_ops ovpn_netdev_ops = {
+ .ndo_open = ovpn_net_open,
+ .ndo_stop = ovpn_net_stop,
+ .ndo_start_xmit = ovpn_net_xmit,
+};
+
+static const struct device_type ovpn_type = {
+ .name = OVPN_FAMILY_NAME,
+};
+
+static const struct nla_policy ovpn_policy[IFLA_OVPN_MAX + 1] = {
+ [IFLA_OVPN_MODE] = NLA_POLICY_RANGE(NLA_U8, OVPN_MODE_P2P,
+ OVPN_MODE_MP),
};

/**
@@ -31,44 +59,119 @@ bool ovpn_dev_is_valid(const struct net_device *dev)
return dev->netdev_ops == &ovpn_netdev_ops;
}

+static void ovpn_setup(struct net_device *dev)
+{
+ netdev_features_t feat = NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_RXCSUM |
+ NETIF_F_GSO | NETIF_F_GSO_SOFTWARE |
+ NETIF_F_HIGHDMA;
+
+ dev->needs_free_netdev = true;
+
+ dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
+
+ dev->netdev_ops = &ovpn_netdev_ops;
+
+ dev->hard_header_len = 0;
+ dev->addr_len = 0;
+ dev->mtu = ETH_DATA_LEN - OVPN_HEAD_ROOM;
+ dev->min_mtu = IPV4_MIN_MTU;
+ dev->max_mtu = IP_MAX_MTU - OVPN_HEAD_ROOM;
+
+ dev->type = ARPHRD_NONE;
+ dev->flags = IFF_POINTOPOINT | IFF_NOARP;
+ dev->priv_flags |= IFF_NO_QUEUE;
+
+ dev->lltx = true;
+ dev->features |= feat;
+ dev->hw_features |= feat;
+ dev->hw_enc_features |= feat;
+
+ dev->needed_headroom = ALIGN(OVPN_HEAD_ROOM, 4);
+ dev->needed_tailroom = OVPN_MAX_PADDING;
+
+ SET_NETDEV_DEVTYPE(dev, &ovpn_type);
+}
+
static int ovpn_newlink(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
- return -EOPNOTSUPP;
+ struct ovpn_priv *ovpn = netdev_priv(dev);
+ enum ovpn_mode mode = OVPN_MODE_P2P;
+
+ if (data && data[IFLA_OVPN_MODE]) {
+ mode = nla_get_u8(data[IFLA_OVPN_MODE]);
+ netdev_dbg(dev, "setting device mode: %u\n", mode);
+ }
+
+ ovpn->dev = dev;
+ ovpn->mode = mode;
+
+ /* turn carrier explicitly off after registration, this way state is
+ * clearly defined
+ */
+ netif_carrier_off(dev);
+
+ return register_netdevice(dev);
+}
+
+static int ovpn_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+ struct ovpn_priv *ovpn = netdev_priv(dev);
+
+ if (nla_put_u8(skb, IFLA_OVPN_MODE, ovpn->mode))
+ return -EMSGSIZE;
+
+ return 0;
}

static struct rtnl_link_ops ovpn_link_ops = {
.kind = "ovpn",
.netns_refund = false,
+ .priv_size = sizeof(struct ovpn_priv),
+ .setup = ovpn_setup,
+ .policy = ovpn_policy,
+ .maxtype = IFLA_OVPN_MAX,
.newlink = ovpn_newlink,
.dellink = unregister_netdevice_queue,
+ .fill_info = ovpn_fill_info,
};

static int ovpn_netdev_notifier_call(struct notifier_block *nb,
unsigned long state, void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct ovpn_priv *ovpn;

if (!ovpn_dev_is_valid(dev))
return NOTIFY_DONE;

+ ovpn = netdev_priv(dev);
+
switch (state) {
case NETDEV_REGISTER:
- /* add device to internal list for later destruction upon
- * unregistration
- */
+ ovpn->registered = true;
break;
case NETDEV_UNREGISTER:
+ /* twiddle thumbs on netns device moves */
+ if (dev->reg_state != NETREG_UNREGISTERING)
+ break;
+
/* can be delivered multiple times, so check registered flag,
* then destroy the interface
*/
+ if (!ovpn->registered)
+ return NOTIFY_DONE;
+
+ netif_carrier_off(dev);
+ ovpn->registered = false;
break;
case NETDEV_POST_INIT:
case NETDEV_GOING_DOWN:
case NETDEV_DOWN:
case NETDEV_UP:
case NETDEV_PRE_UP:
+ break;
default:
return NOTIFY_DONE;
}
diff --git a/drivers/net/ovpn/ovpnstruct.h b/drivers/net/ovpn/ovpnstruct.h
index 1ac4ab512624c6f9907176f3e546448437a8f07f..7dab340444c3dc211a501b788755e050ee571ab9 100644
--- a/drivers/net/ovpn/ovpnstruct.h
+++ b/drivers/net/ovpn/ovpnstruct.h
@@ -10,12 +10,19 @@
#ifndef _NET_OVPN_OVPNSTRUCT_H_
#define _NET_OVPN_OVPNSTRUCT_H_

+#include <uapi/linux/if_link.h>
+#include <uapi/linux/ovpn.h>
+
/**
* struct ovpn_priv - per ovpn interface state
* @dev: the actual netdev representing the tunnel
+ * @registered: whether dev is still registered with netdev or not
+ * @mode: device operation mode (i.e. p2p, mp, ..)
*/
struct ovpn_priv {
struct net_device *dev;
+ bool registered;
+ enum ovpn_mode mode;
};

#endif /* _NET_OVPN_OVPNSTRUCT_H_ */
diff --git a/drivers/net/ovpn/proto.h b/drivers/net/ovpn/proto.h
new file mode 100644
index 0000000000000000000000000000000000000000..00bb3725ac7ab7040c97eb012c2639b2d6967de1
--- /dev/null
+++ b/drivers/net/ovpn/proto.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* OpenVPN data channel offload
+ *
+ * Copyright (C) 2020-2024 OpenVPN, Inc.
+ *
+ * Author: Antonio Quartulli <antonio@openvpn.net>
+ * James Yonan <james@openvpn.net>
+ */
+
+#ifndef _NET_OVPN_PROTO_H_
+#define _NET_OVPN_PROTO_H_
+
+/* When the OpenVPN protocol is ran in AEAD mode, use
+ * the OpenVPN packet ID as the AEAD nonce:
+ *
+ * 00000005 521c3b01 4308c041
+ * [seq # ] [ nonce_tail ]
+ * [ 12-byte full IV ] -> OVPN_NONCE_SIZE
+ * [4-bytes -> OVPN_NONCE_WIRE_SIZE
+ * on wire]
+ */
+
+/* nonce size (96bits) as required by AEAD ciphers */
+#define OVPN_NONCE_SIZE 12
+/* last 8 bytes of AEAD nonce: provided by userspace and usually derived
+ * from key material generated during TLS handshake
+ */
+#define OVPN_NONCE_TAIL_SIZE 8
+
+/* OpenVPN nonce size reduced by 8-byte nonce tail -- this is the
+ * size of the AEAD Associated Data (AD) sent over the wire
+ * and is normally the head of the IV
+ */
+#define OVPN_NONCE_WIRE_SIZE (OVPN_NONCE_SIZE - OVPN_NONCE_TAIL_SIZE)
+
+#define OVPN_OPCODE_SIZE 4 /* DATA_V2 opcode size */
+
+#endif /* _NET_OVPN_PROTO_H_ */
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index bfe880fbbb24bc765bee73212f2c83d53db168e2..27a28de0743cd81c57ccc8af475222da4c4ae38b 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1979,4 +1979,19 @@ enum {

#define IFLA_DSA_MAX (__IFLA_DSA_MAX - 1)

+/* OVPN section */
+
+enum ovpn_mode {
+ OVPN_MODE_P2P,
+ OVPN_MODE_MP,
+};
+
+enum {
+ IFLA_OVPN_UNSPEC,
+ IFLA_OVPN_MODE,
+ __IFLA_OVPN_MAX,
+};
+
+#define IFLA_OVPN_MAX (__IFLA_OVPN_MAX - 1)
+
#endif /* _UAPI_LINUX_IF_LINK_H */

--
2.45.2