/* iptables module for using new netfilter netlink queue
 *
 * (C) 2005 by Harald Welte <laforge@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/module.h>
#include <linux/skbuff.h>

#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/jhash.h>

#include <linux/netfilter.h>
#include <linux/netfilter_arp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_NFQUEUE.h>

MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: packet forwarding to netlink");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_NFQUEUE");
MODULE_ALIAS("ip6t_NFQUEUE");
MODULE_ALIAS("arpt_NFQUEUE");

static u32 jhash_initval __read_mostly;
static bool rnd_inited __read_mostly;

static unsigned int
nfqueue_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_NFQ_info *tinfo = par->targinfo;

        return NF_QUEUE_NR(tinfo->queuenum);
}

static u32 hash_v4(const struct sk_buff *skb)
{
        const struct iphdr *iph = ip_hdr(skb);

        /* packets in either direction go into same queue */
        if ((__force u32)iph->saddr < (__force u32)iph->daddr)
                return jhash_3words((__force u32)iph->saddr,
                        (__force u32)iph->daddr, iph->protocol, jhash_initval);

        return jhash_3words((__force u32)iph->daddr,
                        (__force u32)iph->saddr, iph->protocol, jhash_initval);
}

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static u32 hash_v6(const struct sk_buff *skb)
{
        const struct ipv6hdr *ip6h = ipv6_hdr(skb);
        u32 a, b, c;

        if ((__force u32)ip6h->saddr.s6_addr32[3] <
            (__force u32)ip6h->daddr.s6_addr32[3]) {
                a = (__force u32) ip6h->saddr.s6_addr32[3];
                b = (__force u32) ip6h->daddr.s6_addr32[3];
        } else {
                b = (__force u32) ip6h->saddr.s6_addr32[3];
                a = (__force u32) ip6h->daddr.s6_addr32[3];
        }

        if ((__force u32)ip6h->saddr.s6_addr32[1] <
            (__force u32)ip6h->daddr.s6_addr32[1])
                c = (__force u32) ip6h->saddr.s6_addr32[1];
        else
                c = (__force u32) ip6h->daddr.s6_addr32[1];

        return jhash_3words(a, b, c, jhash_initval);
}
#endif

static u32
nfqueue_hash(const struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_NFQ_info_v1 *info = par->targinfo;
        u32 queue = info->queuenum;

        if (par->family == NFPROTO_IPV4)
                queue += ((u64) hash_v4(skb) * info->queues_total) >> 32;
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
        else if (par->family == NFPROTO_IPV6)
                queue += ((u64) hash_v6(skb) * info->queues_total) >> 32;
#endif

        return queue;
}

static unsigned int
nfqueue_tg_v1(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_NFQ_info_v1 *info = par->targinfo;
        u32 queue = info->queuenum;

        if (info->queues_total > 1)
                queue = nfqueue_hash(skb, par);

        return NF_QUEUE_NR(queue);
}

static unsigned int
nfqueue_tg_v2(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_NFQ_info_v2 *info = par->targinfo;
        unsigned int ret = nfqueue_tg_v1(skb, par);

        if (info->bypass)
                ret |= NF_VERDICT_FLAG_QUEUE_BYPASS;
        return ret;
}

static int nfqueue_tg_check(const struct xt_tgchk_param *par)
{
        const struct xt_NFQ_info_v3 *info = par->targinfo;
        u32 maxid;

        if (unlikely(!rnd_inited)) {
                get_random_bytes(&jhash_initval, sizeof(jhash_initval));
                rnd_inited = true;
        }
        if (info->queues_total == 0) {
                pr_err("NFQUEUE: number of total queues is 0\n");
                return -EINVAL;
        }
        maxid = info->queues_total - 1 + info->queuenum;
        if (maxid > 0xffff) {
                pr_err("NFQUEUE: number of queues (%u) out of range (got %u)\n",
                       info->queues_total, maxid);
                return -ERANGE;
        }
        if (par->target->revision == 2 && info->flags > 1)
                return -EINVAL;
        if (par->target->revision == 3 && info->flags & ~NFQ_FLAG_MASK)
                return -EINVAL;

        return 0;
}

static unsigned int
nfqueue_tg_v3(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_NFQ_info_v3 *info = par->targinfo;
        u32 queue = info->queuenum;

        if (info->queues_total > 1) {
                if (info->flags & NFQ_FLAG_CPU_FANOUT) {
                        int cpu = smp_processor_id();

                        queue = info->queuenum + cpu % info->queues_total;
                } else
                        queue = nfqueue_hash(skb, par);
        }

        return NF_QUEUE_NR(queue);
}

static struct xt_target nfqueue_tg_reg[] __read_mostly = {
        {
                .name           = "NFQUEUE",
                .family         = NFPROTO_UNSPEC,
                .target         = nfqueue_tg,
                .targetsize     = sizeof(struct xt_NFQ_info),
                .me             = THIS_MODULE,
        },
        {
                .name           = "NFQUEUE",
                .revision       = 1,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = nfqueue_tg_check,
                .target         = nfqueue_tg_v1,
                .targetsize     = sizeof(struct xt_NFQ_info_v1),
                .me             = THIS_MODULE,
        },
        {
                .name           = "NFQUEUE",
                .revision       = 2,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = nfqueue_tg_check,
                .target         = nfqueue_tg_v2,
                .targetsize     = sizeof(struct xt_NFQ_info_v2),
                .me             = THIS_MODULE,
        },
        {
                .name           = "NFQUEUE",
                .revision       = 3,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = nfqueue_tg_check,
                .target         = nfqueue_tg_v3,
                .targetsize     = sizeof(struct xt_NFQ_info_v3),
                .me             = THIS_MODULE,
        },
};

static int __init nfqueue_tg_init(void)
{
        return xt_register_targets(nfqueue_tg_reg, ARRAY_SIZE(nfqueue_tg_reg));
}

static void __exit nfqueue_tg_exit(void)
{
        xt_unregister_targets(nfqueue_tg_reg, ARRAY_SIZE(nfqueue_tg_reg));
}

module_init(nfqueue_tg_init);
module_exit(nfqueue_tg_exit);