// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_offload.h>
#include <net/netfilter/nf_dup_netdev.h>

#define NF_RECURSION_LIMIT      2

#ifndef CONFIG_PREEMPT_RT
static u8 *nf_get_nf_dup_skb_recursion(void)
{
        return this_cpu_ptr(&softnet_data.xmit.nf_dup_skb_recursion);
}
#else

static u8 *nf_get_nf_dup_skb_recursion(void)
{
        return &current->net_xmit.nf_dup_skb_recursion;
}

#endif

static void nf_do_netdev_egress(struct sk_buff *skb, struct net_device *dev,
                                enum nf_dev_hooks hook)
{
        u8 *nf_dup_skb_recursion = nf_get_nf_dup_skb_recursion();

        if (*nf_dup_skb_recursion > NF_RECURSION_LIMIT)
                goto err;

        if (hook == NF_NETDEV_INGRESS && skb_mac_header_was_set(skb)) {
                if (skb_cow_head(skb, skb->mac_len))
                        goto err;

                skb_push(skb, skb->mac_len);
        }

        skb->dev = dev;
        skb_clear_tstamp(skb);
        (*nf_dup_skb_recursion)++;
        dev_queue_xmit(skb);
        (*nf_dup_skb_recursion)--;
        return;
err:
        kfree_skb(skb);
}

void nf_fwd_netdev_egress(const struct nft_pktinfo *pkt, int oif)
{
        struct net_device *dev;

        dev = dev_get_by_index_rcu(nft_net(pkt), oif);
        if (!dev) {
                kfree_skb(pkt->skb);
                return;
        }

        nf_do_netdev_egress(pkt->skb, dev, nft_hook(pkt));
}
EXPORT_SYMBOL_GPL(nf_fwd_netdev_egress);

void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif)
{
        struct net_device *dev;
        struct sk_buff *skb;

        dev = dev_get_by_index_rcu(nft_net(pkt), oif);
        if (dev == NULL)
                return;

        skb = skb_clone(pkt->skb, GFP_ATOMIC);
        if (skb)
                nf_do_netdev_egress(skb, dev, nft_hook(pkt));
}
EXPORT_SYMBOL_GPL(nf_dup_netdev_egress);

int nft_fwd_dup_netdev_offload(struct nft_offload_ctx *ctx,
                               struct nft_flow_rule *flow,
                               enum flow_action_id id, int oif)
{
        struct flow_action_entry *entry;
        struct net_device *dev;

        /* nft_flow_rule_destroy() releases the reference on this device. */
        dev = dev_get_by_index(ctx->net, oif);
        if (!dev)
                return -EOPNOTSUPP;

        entry = &flow->rule->action.entries[ctx->num_actions++];
        entry->id = id;
        entry->dev = dev;

        return 0;
}
EXPORT_SYMBOL_GPL(nft_fwd_dup_netdev_offload);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
MODULE_DESCRIPTION("Netfilter packet duplication support");