// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
 * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
 *
 * Extracted from xt_TEE.c
 */
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/netfilter/ipv6/nf_dup_ipv6.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif

static bool nf_dup_ipv6_route(struct net *net, struct sk_buff *skb,
                              const struct in6_addr *gw, int oif)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        struct dst_entry *dst;
        struct flowi6 fl6;

        memset(&fl6, 0, sizeof(fl6));
        if (oif != -1)
                fl6.flowi6_oif = oif;

        fl6.daddr = *gw;
        fl6.flowlabel = (__force __be32)(((iph->flow_lbl[0] & 0xF) << 16) |
                        (iph->flow_lbl[1] << 8) | iph->flow_lbl[2]);
        fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
        dst = ip6_route_output(net, NULL, &fl6);
        if (dst->error) {
                dst_release(dst);
                return false;
        }
        skb_dst_drop(skb);
        skb_dst_set(skb, dst);
        skb->dev      = dst_dev(dst);
        skb->protocol = htons(ETH_P_IPV6);

        return true;
}

void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
                 const struct in6_addr *gw, int oif)
{
        local_bh_disable();
        if (current->in_nf_duplicate)
                goto out;
        skb = pskb_copy(skb, GFP_ATOMIC);
        if (skb == NULL)
                goto out;

#if IS_ENABLED(CONFIG_NF_CONNTRACK)
        nf_reset_ct(skb);
        nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
#endif
        if (hooknum == NF_INET_PRE_ROUTING ||
            hooknum == NF_INET_LOCAL_IN) {
                struct ipv6hdr *iph = ipv6_hdr(skb);
                --iph->hop_limit;
        }
        if (nf_dup_ipv6_route(net, skb, gw, oif)) {
                current->in_nf_duplicate = true;
                ip6_local_out(net, skb->sk, skb);
                current->in_nf_duplicate = false;
        } else {
                kfree_skb(skb);
        }
out:
        local_bh_enable();
}
EXPORT_SYMBOL_GPL(nf_dup_ipv6);

MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("nf_dup_ipv6: IPv6 packet duplication");
MODULE_LICENSE("GPL");