// SPDX-License-Identifier: GPL-2.0-only

#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 <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_tables_core.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nft_fib.h>

#include <net/ip6_fib.h>
#include <net/ip6_route.h>

static int get_ifindex(const struct net_device *dev)
{
        return dev ? dev->ifindex : 0;
}

static int nft_fib6_flowi_init(struct flowi6 *fl6, const struct nft_fib *priv,
                               const struct nft_pktinfo *pkt,
                               const struct net_device *dev,
                               struct ipv6hdr *iph)
{
        int lookup_flags = 0;

        if (priv->flags & NFTA_FIB_F_DADDR) {
                fl6->daddr = iph->daddr;
                fl6->saddr = iph->saddr;
        } else {
                if (nft_hook(pkt) == NF_INET_FORWARD &&
                    priv->flags & NFTA_FIB_F_IIF)
                        fl6->flowi6_iif = nft_out(pkt)->ifindex;

                fl6->daddr = iph->saddr;
                fl6->saddr = iph->daddr;
        }

        if (ipv6_addr_type(&fl6->daddr) & IPV6_ADDR_LINKLOCAL) {
                lookup_flags |= RT6_LOOKUP_F_IFACE;
                fl6->flowi6_oif = get_ifindex(dev ? dev : pkt->skb->dev);
        }

        if (ipv6_addr_type(&fl6->saddr) & IPV6_ADDR_UNICAST)
                lookup_flags |= RT6_LOOKUP_F_HAS_SADDR;

        if (priv->flags & NFTA_FIB_F_MARK)
                fl6->flowi6_mark = pkt->skb->mark;

        fl6->flowlabel = (*(__be32 *)iph) & IPV6_FLOWINFO_MASK;
        fl6->flowi6_l3mdev = nft_fib_l3mdev_master_ifindex_rcu(pkt, dev);

        return lookup_flags;
}

static u32 __nft_fib6_eval_type(const struct nft_fib *priv,
                                const struct nft_pktinfo *pkt,
                                struct ipv6hdr *iph)
{
        const struct net_device *dev = NULL;
        int route_err, addrtype;
        struct rt6_info *rt;
        struct flowi6 fl6 = {
                .flowi6_iif = LOOPBACK_IFINDEX,
                .flowi6_proto = pkt->tprot,
                .flowi6_uid = sock_net_uid(nft_net(pkt), NULL),
        };
        u32 ret = 0;

        if (priv->flags & NFTA_FIB_F_IIF)
                dev = nft_in(pkt);
        else if (priv->flags & NFTA_FIB_F_OIF)
                dev = nft_out(pkt);

        nft_fib6_flowi_init(&fl6, priv, pkt, dev, iph);

        if (dev && nf_ipv6_chk_addr(nft_net(pkt), &fl6.daddr, dev, true))
                ret = RTN_LOCAL;

        route_err = nf_ip6_route(nft_net(pkt), (struct dst_entry **)&rt,
                                 flowi6_to_flowi(&fl6), false);
        if (route_err)
                goto err;

        if (rt->rt6i_flags & RTF_REJECT) {
                route_err = rt->dst.error;
                dst_release(&rt->dst);
                goto err;
        }

        if (ipv6_anycast_destination((struct dst_entry *)rt, &fl6.daddr))
                ret = RTN_ANYCAST;
        else if (!dev && rt->rt6i_flags & RTF_LOCAL)
                ret = RTN_LOCAL;

        dst_release(&rt->dst);

        if (ret)
                return ret;

        addrtype = ipv6_addr_type(&fl6.daddr);

        if (addrtype & IPV6_ADDR_MULTICAST)
                return RTN_MULTICAST;
        if (addrtype & IPV6_ADDR_UNICAST)
                return RTN_UNICAST;

        return RTN_UNSPEC;
 err:
        switch (route_err) {
        case -EINVAL:
                return RTN_BLACKHOLE;
        case -EACCES:
                return RTN_PROHIBIT;
        case -EAGAIN:
                return RTN_THROW;
        default:
                break;
        }

        return RTN_UNREACHABLE;
}

void nft_fib6_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
                        const struct nft_pktinfo *pkt)
{
        const struct nft_fib *priv = nft_expr_priv(expr);
        int noff = skb_network_offset(pkt->skb);
        u32 *dest = &regs->data[priv->dreg];
        struct ipv6hdr *iph, _iph;

        iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
        if (!iph) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        *dest = __nft_fib6_eval_type(priv, pkt, iph);
}
EXPORT_SYMBOL_GPL(nft_fib6_eval_type);

static bool nft_fib_v6_skip_icmpv6(const struct sk_buff *skb, u8 next, const struct ipv6hdr *iph)
{
        if (likely(next != IPPROTO_ICMPV6))
                return false;

        if (ipv6_addr_type(&iph->saddr) != IPV6_ADDR_ANY)
                return false;

        return ipv6_addr_type(&iph->daddr) & IPV6_ADDR_LINKLOCAL;
}

void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
                   const struct nft_pktinfo *pkt)
{
        const struct nft_fib *priv = nft_expr_priv(expr);
        int noff = skb_network_offset(pkt->skb);
        const struct net_device *found = NULL;
        const struct net_device *oif = NULL;
        u32 *dest = &regs->data[priv->dreg];
        struct ipv6hdr *iph, _iph;
        struct flowi6 fl6 = {
                .flowi6_iif = LOOPBACK_IFINDEX,
                .flowi6_proto = pkt->tprot,
                .flowi6_uid = sock_net_uid(nft_net(pkt), NULL),
        };
        struct rt6_info *rt;
        int lookup_flags;

        if (nft_fib_can_skip(pkt)) {
                nft_fib_store_result(dest, priv, nft_in(pkt));
                return;
        }

        if (priv->flags & NFTA_FIB_F_IIF)
                oif = nft_in(pkt);
        else if (priv->flags & NFTA_FIB_F_OIF)
                oif = nft_out(pkt);

        iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
        if (!iph) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        if (nft_fib_v6_skip_icmpv6(pkt->skb, pkt->tprot, iph)) {
                nft_fib_store_result(dest, priv, nft_in(pkt));
                return;
        }

        lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif, iph);

        *dest = 0;
        rt = (void *)ip6_route_lookup(nft_net(pkt), &fl6, pkt->skb,
                                      lookup_flags);
        if (rt->dst.error)
                goto put_rt_err;

        /* Should not see RTF_LOCAL here */
        if (rt->rt6i_flags & (RTF_REJECT | RTF_ANYCAST | RTF_LOCAL))
                goto put_rt_err;

        if (!oif) {
                found = rt->rt6i_idev->dev;
        } else {
                if (oif == rt->rt6i_idev->dev ||
                    l3mdev_master_ifindex_rcu(rt->rt6i_idev->dev) == oif->ifindex)
                        found = oif;
        }

        nft_fib_store_result(dest, priv, found);
 put_rt_err:
        ip6_rt_put(rt);
}
EXPORT_SYMBOL_GPL(nft_fib6_eval);

static struct nft_expr_type nft_fib6_type;

static const struct nft_expr_ops nft_fib6_type_ops = {
        .type           = &nft_fib6_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_fib)),
        .eval           = nft_fib6_eval_type,
        .init           = nft_fib_init,
        .dump           = nft_fib_dump,
        .validate       = nft_fib_validate,
        .reduce         = nft_fib_reduce,
};

static const struct nft_expr_ops nft_fib6_ops = {
        .type           = &nft_fib6_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_fib)),
        .eval           = nft_fib6_eval,
        .init           = nft_fib_init,
        .dump           = nft_fib_dump,
        .validate       = nft_fib_validate,
        .reduce         = nft_fib_reduce,
};

static const struct nft_expr_ops *
nft_fib6_select_ops(const struct nft_ctx *ctx,
                    const struct nlattr * const tb[])
{
        enum nft_fib_result result;

        if (!tb[NFTA_FIB_RESULT])
                return ERR_PTR(-EINVAL);

        result = ntohl(nla_get_be32(tb[NFTA_FIB_RESULT]));

        switch (result) {
        case NFT_FIB_RESULT_OIF:
                return &nft_fib6_ops;
        case NFT_FIB_RESULT_OIFNAME:
                return &nft_fib6_ops;
        case NFT_FIB_RESULT_ADDRTYPE:
                return &nft_fib6_type_ops;
        default:
                return ERR_PTR(-EOPNOTSUPP);
        }
}

static struct nft_expr_type nft_fib6_type __read_mostly = {
        .name           = "fib",
        .select_ops     = nft_fib6_select_ops,
        .policy         = nft_fib_policy,
        .maxattr        = NFTA_FIB_MAX,
        .family         = NFPROTO_IPV6,
        .owner          = THIS_MODULE,
};

static int __init nft_fib6_module_init(void)
{
        return nft_register_expr(&nft_fib6_type);
}

static void __exit nft_fib6_module_exit(void)
{
        nft_unregister_expr(&nft_fib6_type);
}
module_init(nft_fib6_module_init);
module_exit(nft_fib6_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
MODULE_ALIAS_NFT_AF_EXPR(10, "fib");
MODULE_DESCRIPTION("nftables fib / ipv6 route lookup support");