// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PFCP according to 3GPP TS 29.244
 *
 * Copyright (C) 2022, Intel Corporation.
 */

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/types.h>

#include <net/udp.h>
#include <net/udp_tunnel.h>
#include <net/pfcp.h>

struct pfcp_dev {
	struct list_head	list;

	struct sock		*sk;
	struct net_device	*dev;
	struct net		*net;

	struct gro_cells	gro_cells;
};

static unsigned int pfcp_net_id __read_mostly;

struct pfcp_net {
	struct list_head	pfcp_dev_list;
	struct mutex		lock;
};

static void
pfcp_session_recv(struct pfcp_dev *pfcp, struct sk_buff *skb,
		  struct pfcp_metadata *md)
{
	struct pfcphdr_session *unparsed = pfcp_hdr_session(skb);

	md->seid = unparsed->seid;
	md->type = PFCP_TYPE_SESSION;
}

static void
pfcp_node_recv(struct pfcp_dev *pfcp, struct sk_buff *skb,
	       struct pfcp_metadata *md)
{
	md->type = PFCP_TYPE_NODE;
}

static int pfcp_encap_recv(struct sock *sk, struct sk_buff *skb)
{
	IP_TUNNEL_DECLARE_FLAGS(flags) = { };
	struct metadata_dst *tun_dst;
	struct pfcp_metadata *md;
	struct pfcphdr *unparsed;
	struct pfcp_dev *pfcp;

	if (unlikely(!pskb_may_pull(skb, PFCP_HLEN)))
		goto drop;

	pfcp = rcu_dereference_sk_user_data(sk);
	if (unlikely(!pfcp))
		goto drop;

	unparsed = pfcp_hdr(skb);

	ip_tunnel_flags_zero(flags);
	tun_dst = udp_tun_rx_dst(skb, sk->sk_family, flags, 0,
				 sizeof(*md));
	if (unlikely(!tun_dst))
		goto drop;

	md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
	if (unlikely(!md))
		goto drop;

	if (unparsed->flags & PFCP_SEID_FLAG)
		pfcp_session_recv(pfcp, skb, md);
	else
		pfcp_node_recv(pfcp, skb, md);

	__set_bit(IP_TUNNEL_PFCP_OPT_BIT, tun_dst->u.tun_info.key.tun_flags);
	tun_dst->u.tun_info.options_len = sizeof(*md);

	if (unlikely(iptunnel_pull_header(skb, PFCP_HLEN, skb->protocol,
					  !net_eq(sock_net(sk),
					  dev_net(pfcp->dev)))))
		goto drop;

	skb_dst_set(skb, (struct dst_entry *)tun_dst);

	skb_reset_network_header(skb);
	skb_reset_mac_header(skb);
	skb->dev = pfcp->dev;

	gro_cells_receive(&pfcp->gro_cells, skb);

	return 0;
drop:
	kfree_skb(skb);
	return 0;
}

static void pfcp_del_sock(struct pfcp_dev *pfcp)
{
	udp_tunnel_sock_release(pfcp->sk);
	pfcp->sk = NULL;
}

static void pfcp_dev_uninit(struct net_device *dev)
{
	struct pfcp_dev *pfcp = netdev_priv(dev);

	gro_cells_destroy(&pfcp->gro_cells);
	pfcp_del_sock(pfcp);
}

static int pfcp_dev_init(struct net_device *dev)
{
	struct pfcp_dev *pfcp = netdev_priv(dev);

	pfcp->dev = dev;

	return gro_cells_init(&pfcp->gro_cells, dev);
}

static const struct net_device_ops pfcp_netdev_ops = {
	.ndo_init		= pfcp_dev_init,
	.ndo_uninit		= pfcp_dev_uninit,
	.ndo_get_stats64	= dev_get_tstats64,
};

static const struct device_type pfcp_type = {
	.name = "pfcp",
};

static void pfcp_link_setup(struct net_device *dev)
{
	dev->netdev_ops = &pfcp_netdev_ops;
	dev->needs_free_netdev = true;
	SET_NETDEV_DEVTYPE(dev, &pfcp_type);

	dev->hard_header_len = 0;
	dev->addr_len = 0;

	dev->type = ARPHRD_NONE;
	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
	dev->priv_flags |= IFF_NO_QUEUE;

	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
	netif_keep_dst(dev);
}

static struct sock *pfcp_create_sock(struct pfcp_dev *pfcp)
{
	struct udp_tunnel_sock_cfg tuncfg = {};
	struct udp_port_cfg udp_conf = {
		.local_ip.s_addr	= htonl(INADDR_ANY),
		.family			= AF_INET,
	};
	struct net *net = pfcp->net;
	struct socket *sock;
	int err;

	udp_conf.local_udp_port = htons(PFCP_PORT);

	err = udp_sock_create(net, &udp_conf, &sock);
	if (err)
		return ERR_PTR(err);

	tuncfg.sk_user_data = pfcp;
	tuncfg.encap_rcv = pfcp_encap_recv;
	tuncfg.encap_type = 1;

	setup_udp_tunnel_sock(net, sock->sk, &tuncfg);

	return sock->sk;
}

static int pfcp_add_sock(struct pfcp_dev *pfcp)
{
	pfcp->sk = pfcp_create_sock(pfcp);

	return PTR_ERR_OR_ZERO(pfcp->sk);
}

static int pfcp_newlink(struct net_device *dev,
			struct rtnl_newlink_params *params,
			struct netlink_ext_ack *extack)
{
	struct net *link_net = rtnl_newlink_link_net(params);
	struct pfcp_dev *pfcp = netdev_priv(dev);
	struct pfcp_net *pn;
	int err;

	pfcp->net = link_net;

	err = pfcp_add_sock(pfcp);
	if (err) {
		netdev_dbg(dev, "failed to add pfcp socket %d\n", err);
		goto exit_err;
	}

	err = register_netdevice(dev);
	if (err) {
		netdev_dbg(dev, "failed to register pfcp netdev %d\n", err);
		goto exit_del_pfcp_sock;
	}

	pn = net_generic(link_net, pfcp_net_id);

	mutex_lock(&pn->lock);
	list_add(&pfcp->list, &pn->pfcp_dev_list);
	mutex_unlock(&pn->lock);

	netdev_dbg(dev, "registered new PFCP interface\n");

	return 0;

exit_del_pfcp_sock:
	pfcp_del_sock(pfcp);
	synchronize_rcu();
exit_err:
	pfcp->net = NULL;
	return err;
}

static void __pfcp_dellink(struct net *net, struct net_device *dev,
			   struct list_head *head)
{
	struct pfcp_dev *pfcp = netdev_priv(dev);

	list_del_init(&pfcp->list);
	unregister_netdevice_queue_net(net, dev, head);
}

static void pfcp_dellink(struct net_device *dev, struct list_head *head)
{
	struct pfcp_dev *pfcp = netdev_priv(dev);
	struct pfcp_net *pn;

	pn = net_generic(pfcp->net, pfcp_net_id);

	mutex_lock(&pn->lock);
	if (!list_empty(&pfcp->list))
		__pfcp_dellink(dev_net(dev), dev, head);
	mutex_unlock(&pn->lock);
}

static struct rtnl_link_ops pfcp_link_ops __read_mostly = {
	.kind		= "pfcp",
	.priv_size	= sizeof(struct pfcp_dev),
	.setup		= pfcp_link_setup,
	.newlink	= pfcp_newlink,
	.dellink	= pfcp_dellink,
};

static int __net_init pfcp_net_init(struct net *net)
{
	struct pfcp_net *pn = net_generic(net, pfcp_net_id);

	INIT_LIST_HEAD(&pn->pfcp_dev_list);
	mutex_init(&pn->lock);

	return 0;
}

static void __net_exit pfcp_net_exit_rtnl(struct net *net,
					  struct list_head *dev_to_kill)
{
	struct pfcp_net *pn = net_generic(net, pfcp_net_id);
	struct pfcp_dev *pfcp, *pfcp_next;

	mutex_lock(&pn->lock);

	list_for_each_entry_safe(pfcp, pfcp_next, &pn->pfcp_dev_list, list)
		__pfcp_dellink(net, pfcp->dev, dev_to_kill);

	mutex_unlock(&pn->lock);
}

static struct pernet_operations pfcp_net_ops = {
	.init = pfcp_net_init,
	.exit_rtnl = pfcp_net_exit_rtnl,
	.id = &pfcp_net_id,
	.size = sizeof(struct pfcp_net),
};

static int __init pfcp_init(void)
{
	int err;

	err = register_pernet_subsys(&pfcp_net_ops);
	if (err)
		goto exit_err;

	err = rtnl_link_register(&pfcp_link_ops);
	if (err)
		goto exit_unregister_subsys;
	return 0;

exit_unregister_subsys:
	unregister_pernet_subsys(&pfcp_net_ops);
exit_err:
	pr_err("loading PFCP module failed: err %d\n", err);
	return err;
}
late_initcall(pfcp_init);

static void __exit pfcp_exit(void)
{
	rtnl_link_unregister(&pfcp_link_ops);
	unregister_pernet_subsys(&pfcp_net_ops);

	pr_info("PFCP module unloaded\n");
}
module_exit(pfcp_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Wojciech Drewek <wojciech.drewek@intel.com>");
MODULE_DESCRIPTION("Interface driver for PFCP encapsulated traffic");
MODULE_ALIAS_RTNL_LINK("pfcp");