// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <linux/unaligned.h>
#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>

struct nft_byteorder {
        u8                      sreg;
        u8                      dreg;
        enum nft_byteorder_ops  op:8;
        u8                      size;
};

void nft_byteorder_eval(const struct nft_expr *expr,
                        struct nft_regs *regs,
                        const struct nft_pktinfo *pkt)
{
        const struct nft_byteorder *priv = nft_expr_priv(expr);
        const u32 *src = &regs->data[priv->sreg];
        u32 *dst = &regs->data[priv->dreg];

        switch (priv->size) {
        case 8: {
                u64 *dst64 = (void *)dst;
                u64 src64;

                switch (priv->op) {
                case NFT_BYTEORDER_NTOH:
                        src64 = nft_reg_load64(src);

                        nft_reg_store64(dst64, be64_to_cpu((__force __be64)src64));
                        break;
                case NFT_BYTEORDER_HTON:
                        src64 = (__force __u64)cpu_to_be64(nft_reg_load64(src));

                        nft_reg_store64(dst64, src64);
                        break;
                }
                break;
        }
        case 4:
                switch (priv->op) {
                case NFT_BYTEORDER_NTOH:
                        *dst = ntohl((__force __be32)*src);
                        break;
                case NFT_BYTEORDER_HTON:
                        *dst = (__force __u32)htonl(*src);
                        break;
                }
                break;
        case 2:
                switch (priv->op) {
                case NFT_BYTEORDER_NTOH:
                        nft_reg_store16(dst, ntohs(nft_reg_load_be16(src)));
                        break;
                case NFT_BYTEORDER_HTON:
                        nft_reg_store_be16(dst, htons(nft_reg_load16(src)));
                        break;
                }
                break;
        }
}

static const struct nla_policy nft_byteorder_policy[NFTA_BYTEORDER_MAX + 1] = {
        [NFTA_BYTEORDER_SREG]   = NLA_POLICY_MAX(NLA_BE32, NFT_REG32_MAX),
        [NFTA_BYTEORDER_DREG]   = NLA_POLICY_MAX(NLA_BE32, NFT_REG32_MAX),
        [NFTA_BYTEORDER_OP]     = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_BYTEORDER_LEN]    = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_BYTEORDER_SIZE]   = NLA_POLICY_MAX(NLA_BE32, 255),
};

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

        if (tb[NFTA_BYTEORDER_SREG] == NULL ||
            tb[NFTA_BYTEORDER_DREG] == NULL ||
            tb[NFTA_BYTEORDER_LEN] == NULL ||
            tb[NFTA_BYTEORDER_SIZE] == NULL ||
            tb[NFTA_BYTEORDER_OP] == NULL)
                return -EINVAL;

        priv->op = ntohl(nla_get_be32(tb[NFTA_BYTEORDER_OP]));
        switch (priv->op) {
        case NFT_BYTEORDER_NTOH:
        case NFT_BYTEORDER_HTON:
                break;
        default:
                return -EINVAL;
        }

        err = nft_parse_u32_check(tb[NFTA_BYTEORDER_SIZE], U8_MAX, &size);
        if (err < 0)
                return err;

        priv->size = size;

        switch (priv->size) {
        case 2:
        case 4:
        case 8:
                break;
        default:
                return -EINVAL;
        }

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

        /* no longer support multi-reg conversions */
        if (len != size)
                return -EOPNOTSUPP;

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

        err = nft_parse_register_store(ctx, tb[NFTA_BYTEORDER_DREG],
                                       &priv->dreg, NULL, NFT_DATA_VALUE,
                                       len);
        if (err < 0)
                return err;

        if (nft_reg_overlap(priv->sreg, priv->dreg, len))
                return -EINVAL;

        return 0;
}

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

        if (nft_dump_register(skb, NFTA_BYTEORDER_SREG, priv->sreg))
                goto nla_put_failure;
        if (nft_dump_register(skb, NFTA_BYTEORDER_DREG, priv->dreg))
                goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_BYTEORDER_OP, htonl(priv->op)))
                goto nla_put_failure;
        if (nla_put_be32(skb, NFTA_BYTEORDER_SIZE, htonl(priv->size)))
                goto nla_put_failure;
        /* compatibility for old userspace which permitted size != len */
        if (nla_put_be32(skb, NFTA_BYTEORDER_LEN, htonl(priv->size)))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}

static const struct nft_expr_ops nft_byteorder_ops = {
        .type           = &nft_byteorder_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_byteorder)),
        .eval           = nft_byteorder_eval,
        .init           = nft_byteorder_init,
        .dump           = nft_byteorder_dump,
};

struct nft_expr_type nft_byteorder_type __read_mostly = {
        .name           = "byteorder",
        .ops            = &nft_byteorder_ops,
        .policy         = nft_byteorder_policy,
        .maxattr        = NFTA_BYTEORDER_MAX,
        .owner          = THIS_MODULE,
};