// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
 */

#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_core.h>
#include <linux/jhash.h>

struct nft_jhash {
        u8                      sreg;
        u8                      dreg;
        u8                      len;
        bool                    autogen_seed:1;
        u32                     modulus;
        u32                     seed;
        u32                     offset;
};

static void nft_jhash_eval(const struct nft_expr *expr,
                           struct nft_regs *regs,
                           const struct nft_pktinfo *pkt)
{
        struct nft_jhash *priv = nft_expr_priv(expr);
        const void *data = &regs->data[priv->sreg];
        u32 h;

        h = reciprocal_scale(jhash(data, priv->len, priv->seed),
                             priv->modulus);

        regs->data[priv->dreg] = h + priv->offset;
}

struct nft_symhash {
        u8                      dreg;
        u32                     modulus;
        u32                     offset;
};

static void nft_symhash_eval(const struct nft_expr *expr,
                             struct nft_regs *regs,
                             const struct nft_pktinfo *pkt)
{
        struct nft_symhash *priv = nft_expr_priv(expr);
        struct sk_buff *skb = pkt->skb;
        u32 h;

        h = reciprocal_scale(__skb_get_hash_symmetric_net(nft_net(pkt), skb),
                             priv->modulus);

        regs->data[priv->dreg] = h + priv->offset;
}

static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
        [NFTA_HASH_SREG]        = { .type = NLA_U32 },
        [NFTA_HASH_DREG]        = { .type = NLA_U32 },
        [NFTA_HASH_LEN]         = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
        [NFTA_HASH_SEED]        = { .type = NLA_U32 },
        [NFTA_HASH_OFFSET]      = { .type = NLA_U32 },
        [NFTA_HASH_TYPE]        = { .type = NLA_U32 },
};

static int nft_jhash_init(const struct nft_ctx *ctx,
                          const struct nft_expr *expr,
                          const struct nlattr * const tb[])
{
        struct nft_jhash *priv = nft_expr_priv(expr);
        u32 len;
        int err;

        if (!tb[NFTA_HASH_SREG] ||
            !tb[NFTA_HASH_DREG] ||
            !tb[NFTA_HASH_LEN]  ||
            !tb[NFTA_HASH_MODULUS])
                return -EINVAL;

        if (tb[NFTA_HASH_OFFSET])
                priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));

        err = nft_parse_u32_check(tb[NFTA_HASH_LEN], U8_MAX, &len);
        if (err < 0)
                return err;
        if (len == 0)
                return -ERANGE;

        priv->len = len;

        err = nft_parse_register_load(ctx, tb[NFTA_HASH_SREG], &priv->sreg, len);
        if (err < 0)
                return err;

        priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
        if (priv->modulus < 1)
                return -ERANGE;

        if (priv->offset + priv->modulus - 1 < priv->offset)
                return -EOVERFLOW;

        if (tb[NFTA_HASH_SEED]) {
                priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
        } else {
                priv->autogen_seed = true;
                get_random_bytes(&priv->seed, sizeof(priv->seed));
        }

        return nft_parse_register_store(ctx, tb[NFTA_HASH_DREG], &priv->dreg,
                                        NULL, NFT_DATA_VALUE, sizeof(u32));
}

static int nft_symhash_init(const struct nft_ctx *ctx,
                            const struct nft_expr *expr,
                            const struct nlattr * const tb[])
{
        struct nft_symhash *priv = nft_expr_priv(expr);

        if (!tb[NFTA_HASH_DREG]    ||
            !tb[NFTA_HASH_MODULUS])
                return -EINVAL;

        if (tb[NFTA_HASH_OFFSET])
                priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));

        priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
        if (priv->modulus < 1)
                return -ERANGE;

        if (priv->offset + priv->modulus - 1 < priv->offset)
                return -EOVERFLOW;

        return nft_parse_register_store(ctx, tb[NFTA_HASH_DREG],
                                        &priv->dreg, NULL, NFT_DATA_VALUE,
                                        sizeof(u32));
}

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

        if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
                goto nla_put_failure;
        if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
                goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len)))
                goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
                goto nla_put_failure;
        if (!priv->autogen_seed &&
            nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
                goto nla_put_failure;
        if (priv->offset != 0)
                if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
                        goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_JENKINS)))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}

static bool nft_jhash_reduce(struct nft_regs_track *track,
                             const struct nft_expr *expr)
{
        const struct nft_jhash *priv = nft_expr_priv(expr);

        nft_reg_track_cancel(track, priv->dreg, sizeof(u32));

        return false;
}

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

        if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
                goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
                goto nla_put_failure;
        if (priv->offset != 0)
                if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
                        goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_SYM)))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}

static bool nft_symhash_reduce(struct nft_regs_track *track,
                               const struct nft_expr *expr)
{
        struct nft_symhash *priv = nft_expr_priv(expr);
        struct nft_symhash *symhash;

        if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
                nft_reg_track_update(track, expr, priv->dreg, sizeof(u32));
                return false;
        }

        symhash = nft_expr_priv(track->regs[priv->dreg].selector);
        if (priv->offset != symhash->offset ||
            priv->modulus != symhash->modulus) {
                nft_reg_track_update(track, expr, priv->dreg, sizeof(u32));
                return false;
        }

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

        return false;
}

static struct nft_expr_type nft_hash_type;
static const struct nft_expr_ops nft_jhash_ops = {
        .type           = &nft_hash_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_jhash)),
        .eval           = nft_jhash_eval,
        .init           = nft_jhash_init,
        .dump           = nft_jhash_dump,
        .reduce         = nft_jhash_reduce,
};

static const struct nft_expr_ops nft_symhash_ops = {
        .type           = &nft_hash_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_symhash)),
        .eval           = nft_symhash_eval,
        .init           = nft_symhash_init,
        .dump           = nft_symhash_dump,
        .reduce         = nft_symhash_reduce,
};

static const struct nft_expr_ops *
nft_hash_select_ops(const struct nft_ctx *ctx,
                    const struct nlattr * const tb[])
{
        u32 type;

        if (!tb[NFTA_HASH_TYPE])
                return &nft_jhash_ops;

        type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
        switch (type) {
        case NFT_HASH_SYM:
                return &nft_symhash_ops;
        case NFT_HASH_JENKINS:
                return &nft_jhash_ops;
        default:
                break;
        }
        return ERR_PTR(-EOPNOTSUPP);
}

static struct nft_expr_type nft_hash_type __read_mostly = {
        .name           = "hash",
        .select_ops     = nft_hash_select_ops,
        .policy         = nft_hash_policy,
        .maxattr        = NFTA_HASH_MAX,
        .owner          = THIS_MODULE,
};

static int __init nft_hash_module_init(void)
{
        return nft_register_expr(&nft_hash_type);
}

static void __exit nft_hash_module_exit(void)
{
        nft_unregister_expr(&nft_hash_type);
}

module_init(nft_hash_module_init);
module_exit(nft_hash_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
MODULE_ALIAS_NFT_EXPR("hash");
MODULE_DESCRIPTION("Netfilter nftables hash module");