/*
 * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <net/netfilter/nf_tables.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <net/netfilter/nf_tables_ipv4.h>
#include <net/netfilter/nf_tables_ipv6.h>

static inline void
nft_netdev_set_pktinfo_ipv4(struct nft_pktinfo *pkt,
			    struct sk_buff *skb,
			    const struct nf_hook_state *state)
{
	struct iphdr *iph, _iph;
	u32 len, thoff;

	nft_set_pktinfo(pkt, skb, state);

	iph = skb_header_pointer(skb, skb_network_offset(skb), sizeof(*iph),
				 &_iph);
	if (!iph)
		return;

	iph = ip_hdr(skb);
	if (iph->ihl < 5 || iph->version != 4)
		return;

	len = ntohs(iph->tot_len);
	thoff = iph->ihl * 4;
	if (skb->len < len)
		return;
	else if (len < thoff)
		return;

	pkt->tprot = iph->protocol;
	pkt->xt.thoff = thoff;
	pkt->xt.fragoff = ntohs(iph->frag_off) & IP_OFFSET;
}

static inline void
__nft_netdev_set_pktinfo_ipv6(struct nft_pktinfo *pkt,
			      struct sk_buff *skb,
			      const struct nf_hook_state *state)
{
#if IS_ENABLED(CONFIG_IPV6)
	struct ipv6hdr *ip6h, _ip6h;
	unsigned int thoff = 0;
	unsigned short frag_off;
	int protohdr;
	u32 pkt_len;

	ip6h = skb_header_pointer(skb, skb_network_offset(skb), sizeof(*ip6h),
				  &_ip6h);
	if (!ip6h)
		return;

	if (ip6h->version != 6)
		return;

	pkt_len = ntohs(ip6h->payload_len);
	if (pkt_len + sizeof(*ip6h) > skb->len)
		return;

	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, NULL);
	if (protohdr < 0)
                return;

	pkt->tprot = protohdr;
	pkt->xt.thoff = thoff;
	pkt->xt.fragoff = frag_off;
#endif
}

static inline void nft_netdev_set_pktinfo_ipv6(struct nft_pktinfo *pkt,
					       struct sk_buff *skb,
					       const struct nf_hook_state *state)
{
	nft_set_pktinfo(pkt, skb, state);
	__nft_netdev_set_pktinfo_ipv6(pkt, skb, state);
}

static unsigned int
nft_do_chain_netdev(void *priv, struct sk_buff *skb,
		    const struct nf_hook_state *state)
{
	struct nft_pktinfo pkt;

	switch (eth_hdr(skb)->h_proto) {
	case htons(ETH_P_IP):
		nft_netdev_set_pktinfo_ipv4(&pkt, skb, state);
		break;
	case htons(ETH_P_IPV6):
		nft_netdev_set_pktinfo_ipv6(&pkt, skb, state);
		break;
	default:
		nft_set_pktinfo(&pkt, skb, state);
		break;
	}

	return nft_do_chain(&pkt, priv);
}

static struct nft_af_info nft_af_netdev __read_mostly = {
	.family		= NFPROTO_NETDEV,
	.nhooks		= NF_NETDEV_NUMHOOKS,
	.owner		= THIS_MODULE,
	.flags		= NFT_AF_NEEDS_DEV,
	.nops		= 1,
	.hooks		= {
		[NF_NETDEV_INGRESS]	= nft_do_chain_netdev,
	},
};

static int nf_tables_netdev_init_net(struct net *net)
{
	net->nft.netdev = kmalloc(sizeof(struct nft_af_info), GFP_KERNEL);
	if (net->nft.netdev == NULL)
		return -ENOMEM;

	memcpy(net->nft.netdev, &nft_af_netdev, sizeof(nft_af_netdev));

	if (nft_register_afinfo(net, net->nft.netdev) < 0)
		goto err;

	return 0;
err:
	kfree(net->nft.netdev);
	return -ENOMEM;
}

static void nf_tables_netdev_exit_net(struct net *net)
{
	nft_unregister_afinfo(net->nft.netdev);
	kfree(net->nft.netdev);
}

static struct pernet_operations nf_tables_netdev_net_ops = {
	.init	= nf_tables_netdev_init_net,
	.exit	= nf_tables_netdev_exit_net,
};

static const struct nf_chain_type nft_filter_chain_netdev = {
	.name		= "filter",
	.type		= NFT_CHAIN_T_DEFAULT,
	.family		= NFPROTO_NETDEV,
	.owner		= THIS_MODULE,
	.hook_mask	= (1 << NF_NETDEV_INGRESS),
};

static void nft_netdev_event(unsigned long event, struct nft_af_info *afi,
			     struct net_device *dev, struct nft_table *table,
			     struct nft_base_chain *basechain)
{
	switch (event) {
	case NETDEV_REGISTER:
		if (strcmp(basechain->dev_name, dev->name) != 0)
			return;

		BUG_ON(!(basechain->flags & NFT_BASECHAIN_DISABLED));

		dev_hold(dev);
		basechain->ops[0].dev = dev;
		basechain->flags &= ~NFT_BASECHAIN_DISABLED;
		if (!(table->flags & NFT_TABLE_F_DORMANT))
			nft_register_basechain(basechain, afi->nops);
		break;
	case NETDEV_UNREGISTER:
		if (strcmp(basechain->dev_name, dev->name) != 0)
			return;

		BUG_ON(basechain->flags & NFT_BASECHAIN_DISABLED);

		if (!(table->flags & NFT_TABLE_F_DORMANT))
			nft_unregister_basechain(basechain, afi->nops);

		dev_put(basechain->ops[0].dev);
		basechain->ops[0].dev = NULL;
		basechain->flags |= NFT_BASECHAIN_DISABLED;
		break;
	case NETDEV_CHANGENAME:
		if (dev->ifindex != basechain->ops[0].dev->ifindex)
			return;

		strncpy(basechain->dev_name, dev->name, IFNAMSIZ);
		break;
	}
}

static int nf_tables_netdev_event(struct notifier_block *this,
				  unsigned long event, void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct nft_af_info *afi;
	struct nft_table *table;
	struct nft_chain *chain;

	nfnl_lock(NFNL_SUBSYS_NFTABLES);
	list_for_each_entry(afi, &dev_net(dev)->nft.af_info, list) {
		if (afi->family != NFPROTO_NETDEV)
			continue;

		list_for_each_entry(table, &afi->tables, list) {
			list_for_each_entry(chain, &table->chains, list) {
				if (!(chain->flags & NFT_BASE_CHAIN))
					continue;

				nft_netdev_event(event, afi, dev, table,
						 nft_base_chain(chain));
			}
		}
	}
	nfnl_unlock(NFNL_SUBSYS_NFTABLES);

	return NOTIFY_DONE;
}

static struct notifier_block nf_tables_netdev_notifier = {
	.notifier_call	= nf_tables_netdev_event,
};

static int __init nf_tables_netdev_init(void)
{
	int ret;

	nft_register_chain_type(&nft_filter_chain_netdev);
	ret = register_pernet_subsys(&nf_tables_netdev_net_ops);
	if (ret < 0)
		nft_unregister_chain_type(&nft_filter_chain_netdev);

	register_netdevice_notifier(&nf_tables_netdev_notifier);

	return ret;
}

static void __exit nf_tables_netdev_exit(void)
{
	unregister_netdevice_notifier(&nf_tables_netdev_notifier);
	unregister_pernet_subsys(&nf_tables_netdev_net_ops);
	nft_unregister_chain_type(&nft_filter_chain_netdev);
}

module_init(nf_tables_netdev_init);
module_exit(nf_tables_netdev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
MODULE_ALIAS_NFT_FAMILY(5); /* NFPROTO_NETDEV */