/*
 * Copyright (c) 2013 Nicira, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/kconfig.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/if_arp.h>
#include <linux/mroute.h>
#include <linux/init.h>
#include <linux/in6.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/rculist.h>
#include <linux/err.h>

#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/protocol.h>
#include <net/ip_tunnels.h>
#include <net/arp.h>
#include <net/checksum.h>
#include <net/dsfield.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/rtnetlink.h>
#include <net/udp.h>

#if IS_ENABLED(CONFIG_IPV6)
#include <net/ipv6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#endif

#include "compat.h"

#ifndef HAVE_METADATA_DST
static void ip_tunnel_add(struct ip_tunnel_net *itn, struct ip_tunnel *t)
{
	if (t->collect_md)
		rcu_assign_pointer(itn->collect_md_tun, t);
	else
		WARN_ONCE(1, "%s: collect md not set\n", t->dev->name);
}

static void ip_tunnel_del(struct ip_tunnel_net *itn, struct ip_tunnel *t)
{
	if (t->collect_md)
		rcu_assign_pointer(itn->collect_md_tun, NULL);
}

static inline void init_tunnel_flow(struct flowi4 *fl4,
				    int proto,
				    __be32 daddr, __be32 saddr,
				    __be32 key, __u8 tos, int oif)
{
	memset(fl4, 0, sizeof(*fl4));
	fl4->flowi4_oif = oif;
	fl4->daddr = daddr;
	fl4->saddr = saddr;
	fl4->flowi4_tos = tos;
	fl4->flowi4_proto = proto;
	fl4->fl4_gre_key = key;
}

static int ip_tunnel_bind_dev(struct net_device *dev)
{
	struct net_device *tdev = NULL;
	struct ip_tunnel *tunnel = netdev_priv(dev);
	const struct iphdr *iph;
	int hlen = LL_MAX_HEADER;
	int mtu = ETH_DATA_LEN;
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	iph = &tunnel->parms.iph;

	/* Guess output device to choose reasonable mtu and needed_headroom */
	if (iph->daddr) {
		struct flowi4 fl4;
		struct rtable *rt;

		init_tunnel_flow(&fl4, iph->protocol, iph->daddr,
				 iph->saddr, tunnel->parms.o_key,
				 RT_TOS(iph->tos), tunnel->parms.link);
		rt = ip_route_output_key(tunnel->net, &fl4);

		if (!IS_ERR(rt)) {
			tdev = rt->dst.dev;
			ip_rt_put(rt);
		}
		if (dev->type != ARPHRD_ETHER)
			dev->flags |= IFF_POINTOPOINT;
	}

	if (!tdev && tunnel->parms.link)
		tdev = __dev_get_by_index(tunnel->net, tunnel->parms.link);

	if (tdev) {
		hlen = tdev->hard_header_len + tdev->needed_headroom;
		mtu = tdev->mtu;
	}

	dev->needed_headroom = t_hlen + hlen;
	mtu -= (dev->hard_header_len + t_hlen);

	if (mtu < 68)
		mtu = 68;

	return mtu;
}

int rpl___ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	int t_hlen = tunnel->hlen + sizeof(struct iphdr);
	int max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;

	if (new_mtu < 68)
		return -EINVAL;

	if (new_mtu > max_mtu) {
		if (strict)
			return -EINVAL;

		new_mtu = max_mtu;
	}

	dev->mtu = new_mtu;
	return 0;
}

int rpl_ip_tunnel_change_mtu(struct net_device *dev, int new_mtu)
{
	return rpl___ip_tunnel_change_mtu(dev, new_mtu, true);
}

static void ip_tunnel_dev_free(struct net_device *dev)
{
	free_percpu(dev->tstats);
	free_netdev(dev);
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,39)
void rpl_ip_tunnel_dellink(struct net_device *dev, struct list_head *head)
#else
void rpl_ip_tunnel_dellink(struct net_device *dev)
#endif
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct ip_tunnel_net *itn;

	itn = net_generic(tunnel->net, tunnel->ip_tnl_net_id);

	ip_tunnel_del(itn, netdev_priv(dev));
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,39)
	unregister_netdevice_queue(dev, head);
#endif
}

int rpl_ip_tunnel_init_net(struct net *net, int ip_tnl_net_id,
				  struct rtnl_link_ops *ops, char *devname)
{
	struct ip_tunnel_net *itn = net_generic(net, ip_tnl_net_id);

	itn->collect_md_tun = NULL;
	itn->rtnl_ops = ops;
	return 0;
}

static void ip_tunnel_destroy(struct ip_tunnel_net *itn, struct list_head *head,
			      struct rtnl_link_ops *ops)
{
	struct ip_tunnel *t;

	t = rtnl_dereference(itn->collect_md_tun);
	if (!t)
		return;
	unregister_netdevice_queue(t->dev, head);
}

void rpl_ip_tunnel_delete_net(struct ip_tunnel_net *itn, struct rtnl_link_ops *ops)
{
	LIST_HEAD(list);

	rtnl_lock();
	ip_tunnel_destroy(itn, &list, ops);
	unregister_netdevice_many(&list);
	rtnl_unlock();
}

int rpl_ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
		      struct ip_tunnel_parm *p)
{
	struct ip_tunnel *nt;
	struct net *net = dev_net(dev);
	struct ip_tunnel_net *itn;
	int mtu;
	int err;

	nt = netdev_priv(dev);
	itn = net_generic(net, nt->ip_tnl_net_id);

	if (nt->collect_md) {
		if (rtnl_dereference(itn->collect_md_tun))
			return -EEXIST;
	} else {
		return -EOPNOTSUPP;
	}

	nt->net = net;
	nt->parms = *p;
	err = register_netdevice(dev);
	if (err)
		goto out;

	if (dev->type == ARPHRD_ETHER && !tb[IFLA_ADDRESS])
		eth_hw_addr_random(dev);

	mtu = ip_tunnel_bind_dev(dev);
	if (!tb[IFLA_MTU])
		dev->mtu = mtu;

	ip_tunnel_add(itn, nt);
out:
	return err;
}

int rpl_ip_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct iphdr *iph = &tunnel->parms.iph;

	dev->destructor	= ip_tunnel_dev_free;
	dev->tstats = (typeof(dev->tstats)) netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
	if (!dev->tstats)
		return -ENOMEM;
	tunnel->dev = dev;
	tunnel->net = dev_net(dev);
	strcpy(tunnel->parms.name, dev->name);
	iph->version		= 4;
	iph->ihl		= 5;

	if (tunnel->collect_md)
		dev->features |= NETIF_F_NETNS_LOCAL;

	return 0;
}

void rpl_ip_tunnel_uninit(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct net *net = tunnel->net;
	struct ip_tunnel_net *itn;

	itn = net_generic(net, tunnel->ip_tnl_net_id);
	ip_tunnel_del(itn, netdev_priv(dev));
}

/* Do least required initialization, rest of init is done in tunnel_init call */
void rpl_ip_tunnel_setup(struct net_device *dev, int net_id)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);

	tunnel->ip_tnl_net_id = net_id;
}

int rpl_ip_tunnel_get_iflink(const struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);

	return tunnel->parms.link;
}

struct net *rpl_ip_tunnel_get_link_net(const struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);

	return tunnel->net;
}

#endif