// SPDX-License-Identifier: GPL-2.0
/*  OpenVPN data channel offload
 *
 *  Copyright (C) 2020-2025 OpenVPN, Inc.
 *
 *  Author:     Antonio Quartulli <antonio@openvpn.net>
 *              James Yonan <james@openvpn.net>
 */

#include <linux/ethtool.h>
#include <linux/genetlink.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <net/gro_cells.h>
#include <net/ip.h>
#include <net/rtnetlink.h>
#include <uapi/linux/if_arp.h>

#include "ovpnpriv.h"
#include "main.h"
#include "netlink.h"
#include "io.h"
#include "peer.h"
#include "proto.h"
#include "tcp.h"
#include "udp.h"

static void ovpn_priv_free(struct net_device *net)
{
        struct ovpn_priv *ovpn = netdev_priv(net);

        kfree(ovpn->peers);
}

static int ovpn_mp_alloc(struct ovpn_priv *ovpn)
{
        struct in_device *dev_v4;
        int i;

        if (ovpn->mode != OVPN_MODE_MP)
                return 0;

        dev_v4 = __in_dev_get_rtnl(ovpn->dev);
        if (dev_v4) {
                /* disable redirects as Linux gets confused by ovpn
                 * handling same-LAN routing.
                 * This happens because a multipeer interface is used as
                 * relay point between hosts in the same subnet, while
                 * in a classic LAN this would not be needed because the
                 * two hosts would be able to talk directly.
                 */
                IN_DEV_CONF_SET(dev_v4, SEND_REDIRECTS, false);
                IPV4_DEVCONF_ALL(dev_net(ovpn->dev), SEND_REDIRECTS) = false;
        }

        /* the peer container is fairly large, therefore we allocate it only in
         * MP mode
         */
        ovpn->peers = kzalloc_obj(*ovpn->peers);
        if (!ovpn->peers)
                return -ENOMEM;

        for (i = 0; i < ARRAY_SIZE(ovpn->peers->by_id); i++) {
                INIT_HLIST_HEAD(&ovpn->peers->by_id[i]);
                INIT_HLIST_NULLS_HEAD(&ovpn->peers->by_vpn_addr4[i], i);
                INIT_HLIST_NULLS_HEAD(&ovpn->peers->by_vpn_addr6[i], i);
                INIT_HLIST_NULLS_HEAD(&ovpn->peers->by_transp_addr[i], i);
        }

        return 0;
}

static int ovpn_net_init(struct net_device *dev)
{
        struct ovpn_priv *ovpn = netdev_priv(dev);
        int err = gro_cells_init(&ovpn->gro_cells, dev);

        if (err < 0)
                return err;

        err = ovpn_mp_alloc(ovpn);
        if (err < 0) {
                gro_cells_destroy(&ovpn->gro_cells);
                return err;
        }

        return 0;
}

static void ovpn_net_uninit(struct net_device *dev)
{
        struct ovpn_priv *ovpn = netdev_priv(dev);

        disable_delayed_work_sync(&ovpn->keepalive_work);
        ovpn_peers_free(ovpn, NULL, OVPN_DEL_PEER_REASON_TEARDOWN);
        gro_cells_destroy(&ovpn->gro_cells);
}

static const struct net_device_ops ovpn_netdev_ops = {
        .ndo_init               = ovpn_net_init,
        .ndo_uninit             = ovpn_net_uninit,
        .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),
};

/**
 * ovpn_dev_is_valid - check if the netdevice is of type 'ovpn'
 * @dev: the interface to check
 *
 * Return: whether the netdevice is of type 'ovpn'
 */
bool ovpn_dev_is_valid(const struct net_device *dev)
{
        return dev->netdev_ops == &ovpn_netdev_ops;
}

static void ovpn_get_drvinfo(struct net_device *dev,
                             struct ethtool_drvinfo *info)
{
        strscpy(info->driver, "ovpn", sizeof(info->driver));
        strscpy(info->bus_info, "ovpn", sizeof(info->bus_info));
}

static const struct ethtool_ops ovpn_ethtool_ops = {
        .get_drvinfo            = ovpn_get_drvinfo,
        .get_link               = ethtool_op_get_link,
        .get_ts_info            = ethtool_op_get_ts_info,
};

static void ovpn_setup(struct net_device *dev)
{
        netdev_features_t feat = NETIF_F_SG | NETIF_F_GSO |
                                 NETIF_F_GSO_SOFTWARE | NETIF_F_HIGHDMA;

        dev->needs_free_netdev = true;

        dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;

        dev->ethtool_ops = &ovpn_ethtool_ops;
        dev->netdev_ops = &ovpn_netdev_ops;

        dev->priv_destructor = ovpn_priv_free;

        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;
        /* when routing packets to a LAN behind a client, we rely on the
         * route entry that originally brought the packet into ovpn, so
         * don't release it
         */
        netif_keep_dst(dev);

        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_device *dev,
                        struct rtnl_newlink_params *params,
                        struct netlink_ext_ack *extack)
{
        struct ovpn_priv *ovpn = netdev_priv(dev);
        struct nlattr **data = params->data;
        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;
        spin_lock_init(&ovpn->lock);
        INIT_DELAYED_WORK(&ovpn->keepalive_work, ovpn_peer_keepalive_work);

        /* Set carrier explicitly after registration, this way state is
         * clearly defined.
         *
         * In case of MP interfaces we keep the carrier always on.
         *
         * Carrier for P2P interfaces is initially off and it is then
         * switched on and off when the remote peer is added or deleted.
         */
        if (ovpn->mode == OVPN_MODE_MP)
                netif_carrier_on(dev);
        else
                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,
        .fill_info = ovpn_fill_info,
};

static int __init ovpn_init(void)
{
        int err = rtnl_link_register(&ovpn_link_ops);

        if (err) {
                pr_err("ovpn: can't register rtnl link ops: %d\n", err);
                return err;
        }

        err = ovpn_nl_register();
        if (err) {
                pr_err("ovpn: can't register netlink family: %d\n", err);
                goto unreg_rtnl;
        }

        ovpn_tcp_init();

        return 0;

unreg_rtnl:
        rtnl_link_unregister(&ovpn_link_ops);
        return err;
}

static __exit void ovpn_cleanup(void)
{
        ovpn_nl_unregister();
        rtnl_link_unregister(&ovpn_link_ops);

        rcu_barrier();
}

module_init(ovpn_init);
module_exit(ovpn_cleanup);

MODULE_DESCRIPTION("OpenVPN data channel offload (ovpn)");
MODULE_AUTHOR("Antonio Quartulli <antonio@openvpn.net>");
MODULE_LICENSE("GPL");