// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Generic part shared by ipv4 and ipv6 backends.
 */

#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_core.h>
#include <net/netfilter/nf_tables.h>
#include <linux/in.h>
#include <net/xfrm.h>

static const struct nla_policy nft_xfrm_policy[NFTA_XFRM_MAX + 1] = {
        [NFTA_XFRM_KEY]         = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_XFRM_DIR]         = { .type = NLA_U8 },
        [NFTA_XFRM_SPNUM]       = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_XFRM_DREG]        = { .type = NLA_U32 },
};

struct nft_xfrm {
        enum nft_xfrm_keys      key:8;
        u8                      dreg;
        u8                      dir;
        u8                      spnum;
        u8                      len;
};

static int nft_xfrm_get_init(const struct nft_ctx *ctx,
                             const struct nft_expr *expr,
                             const struct nlattr * const tb[])
{
        struct nft_xfrm *priv = nft_expr_priv(expr);
        unsigned int len = 0;
        u32 spnum = 0;
        u8 dir;

        if (!tb[NFTA_XFRM_KEY] || !tb[NFTA_XFRM_DIR] || !tb[NFTA_XFRM_DREG])
                return -EINVAL;

        switch (ctx->family) {
        case NFPROTO_IPV4:
        case NFPROTO_IPV6:
        case NFPROTO_INET:
                break;
        default:
                return -EOPNOTSUPP;
        }

        priv->key = ntohl(nla_get_be32(tb[NFTA_XFRM_KEY]));
        switch (priv->key) {
        case NFT_XFRM_KEY_REQID:
        case NFT_XFRM_KEY_SPI:
                len = sizeof(u32);
                break;
        case NFT_XFRM_KEY_DADDR_IP4:
        case NFT_XFRM_KEY_SADDR_IP4:
                len = sizeof(struct in_addr);
                break;
        case NFT_XFRM_KEY_DADDR_IP6:
        case NFT_XFRM_KEY_SADDR_IP6:
                len = sizeof(struct in6_addr);
                break;
        default:
                return -EINVAL;
        }

        dir = nla_get_u8(tb[NFTA_XFRM_DIR]);
        switch (dir) {
        case XFRM_POLICY_IN:
        case XFRM_POLICY_OUT:
                priv->dir = dir;
                break;
        default:
                return -EINVAL;
        }

        if (tb[NFTA_XFRM_SPNUM])
                spnum = ntohl(nla_get_be32(tb[NFTA_XFRM_SPNUM]));

        if (spnum >= XFRM_MAX_DEPTH)
                return -ERANGE;

        priv->spnum = spnum;

        priv->len = len;
        return nft_parse_register_store(ctx, tb[NFTA_XFRM_DREG], &priv->dreg,
                                        NULL, NFT_DATA_VALUE, len);
}

/* Return true if key asks for daddr/saddr and current
 * state does have a valid address (BEET, TUNNEL).
 */
static bool xfrm_state_addr_ok(enum nft_xfrm_keys k, u8 family, u8 mode)
{
        switch (k) {
        case NFT_XFRM_KEY_DADDR_IP4:
        case NFT_XFRM_KEY_SADDR_IP4:
                if (family == NFPROTO_IPV4)
                        break;
                return false;
        case NFT_XFRM_KEY_DADDR_IP6:
        case NFT_XFRM_KEY_SADDR_IP6:
                if (family == NFPROTO_IPV6)
                        break;
                return false;
        default:
                return true;
        }

        return mode == XFRM_MODE_BEET || mode == XFRM_MODE_TUNNEL ||
               mode == XFRM_MODE_IPTFS;
}

static void nft_xfrm_state_get_key(const struct nft_xfrm *priv,
                                   struct nft_regs *regs,
                                   const struct xfrm_state *state)
{
        u32 *dest = &regs->data[priv->dreg];

        if (!xfrm_state_addr_ok(priv->key,
                                state->props.family,
                                state->props.mode)) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        switch (priv->key) {
        case NFT_XFRM_KEY_UNSPEC:
        case __NFT_XFRM_KEY_MAX:
                WARN_ON_ONCE(1);
                break;
        case NFT_XFRM_KEY_DADDR_IP4:
                *dest = (__force __u32)state->id.daddr.a4;
                return;
        case NFT_XFRM_KEY_DADDR_IP6:
                memcpy(dest, &state->id.daddr.in6, sizeof(struct in6_addr));
                return;
        case NFT_XFRM_KEY_SADDR_IP4:
                *dest = (__force __u32)state->props.saddr.a4;
                return;
        case NFT_XFRM_KEY_SADDR_IP6:
                memcpy(dest, &state->props.saddr.in6, sizeof(struct in6_addr));
                return;
        case NFT_XFRM_KEY_REQID:
                *dest = state->props.reqid;
                return;
        case NFT_XFRM_KEY_SPI:
                *dest = (__force __u32)state->id.spi;
                return;
        }

        regs->verdict.code = NFT_BREAK;
}

static void nft_xfrm_get_eval_in(const struct nft_xfrm *priv,
                                    struct nft_regs *regs,
                                    const struct nft_pktinfo *pkt)
{
        const struct sec_path *sp = skb_sec_path(pkt->skb);
        const struct xfrm_state *state;

        if (sp == NULL || sp->len <= priv->spnum) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        state = sp->xvec[priv->spnum];
        nft_xfrm_state_get_key(priv, regs, state);
}

static void nft_xfrm_get_eval_out(const struct nft_xfrm *priv,
                                  struct nft_regs *regs,
                                  const struct nft_pktinfo *pkt)
{
        const struct dst_entry *dst = skb_dst(pkt->skb);
        int i;

        for (i = 0; dst && dst->xfrm;
             dst = ((const struct xfrm_dst *)dst)->child, i++) {
                if (i < priv->spnum)
                        continue;

                nft_xfrm_state_get_key(priv, regs, dst->xfrm);
                return;
        }

        regs->verdict.code = NFT_BREAK;
}

static void nft_xfrm_get_eval(const struct nft_expr *expr,
                              struct nft_regs *regs,
                              const struct nft_pktinfo *pkt)
{
        const struct nft_xfrm *priv = nft_expr_priv(expr);

        switch (priv->dir) {
        case XFRM_POLICY_IN:
                nft_xfrm_get_eval_in(priv, regs, pkt);
                break;
        case XFRM_POLICY_OUT:
                nft_xfrm_get_eval_out(priv, regs, pkt);
                break;
        default:
                WARN_ON_ONCE(1);
                regs->verdict.code = NFT_BREAK;
                break;
        }
}

static int nft_xfrm_get_dump(struct sk_buff *skb,
                             const struct nft_expr *expr, bool reset)
{
        const struct nft_xfrm *priv = nft_expr_priv(expr);

        if (nft_dump_register(skb, NFTA_XFRM_DREG, priv->dreg))
                return -1;

        if (nla_put_be32(skb, NFTA_XFRM_KEY, htonl(priv->key)))
                return -1;
        if (nla_put_u8(skb, NFTA_XFRM_DIR, priv->dir))
                return -1;
        if (nla_put_be32(skb, NFTA_XFRM_SPNUM, htonl(priv->spnum)))
                return -1;

        return 0;
}

static int nft_xfrm_validate(const struct nft_ctx *ctx, const struct nft_expr *expr)
{
        const struct nft_xfrm *priv = nft_expr_priv(expr);
        unsigned int hooks;

        if (ctx->family != NFPROTO_IPV4 &&
            ctx->family != NFPROTO_IPV6 &&
            ctx->family != NFPROTO_INET)
                return -EOPNOTSUPP;

        switch (priv->dir) {
        case XFRM_POLICY_IN:
                hooks = (1 << NF_INET_FORWARD) |
                        (1 << NF_INET_LOCAL_IN) |
                        (1 << NF_INET_PRE_ROUTING);
                break;
        case XFRM_POLICY_OUT:
                hooks = (1 << NF_INET_FORWARD) |
                        (1 << NF_INET_LOCAL_OUT) |
                        (1 << NF_INET_POST_ROUTING);
                break;
        default:
                WARN_ON_ONCE(1);
                return -EINVAL;
        }

        return nft_chain_validate_hooks(ctx->chain, hooks);
}

static bool nft_xfrm_reduce(struct nft_regs_track *track,
                            const struct nft_expr *expr)
{
        const struct nft_xfrm *priv = nft_expr_priv(expr);
        const struct nft_xfrm *xfrm;

        if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
                nft_reg_track_update(track, expr, priv->dreg, priv->len);
                return false;
        }

        xfrm = nft_expr_priv(track->regs[priv->dreg].selector);
        if (priv->key != xfrm->key ||
            priv->dreg != xfrm->dreg ||
            priv->dir != xfrm->dir ||
            priv->spnum != xfrm->spnum) {
                nft_reg_track_update(track, expr, priv->dreg, priv->len);
                return false;
        }

        if (!track->regs[priv->dreg].bitwise)
                return true;

        return nft_expr_reduce_bitwise(track, expr);
}

static struct nft_expr_type nft_xfrm_type;
static const struct nft_expr_ops nft_xfrm_get_ops = {
        .type           = &nft_xfrm_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_xfrm)),
        .eval           = nft_xfrm_get_eval,
        .init           = nft_xfrm_get_init,
        .dump           = nft_xfrm_get_dump,
        .validate       = nft_xfrm_validate,
        .reduce         = nft_xfrm_reduce,
};

static struct nft_expr_type nft_xfrm_type __read_mostly = {
        .name           = "xfrm",
        .ops            = &nft_xfrm_get_ops,
        .policy         = nft_xfrm_policy,
        .maxattr        = NFTA_XFRM_MAX,
        .owner          = THIS_MODULE,
};

static int __init nft_xfrm_module_init(void)
{
        return nft_register_expr(&nft_xfrm_type);
}

static void __exit nft_xfrm_module_exit(void)
{
        nft_unregister_expr(&nft_xfrm_type);
}

module_init(nft_xfrm_module_init);
module_exit(nft_xfrm_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("nf_tables: xfrm/IPSec matching");
MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
MODULE_AUTHOR("Máté Eckl <ecklm94@gmail.com>");
MODULE_ALIAS_NFT_EXPR("xfrm");