/*
 * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Development of this code funded by Astaro AG (http://www.astaro.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_core.h>
#include <net/netfilter/nf_tables.h>

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

static 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);
	u32 *src = &regs->data[priv->sreg];
	u32 *dst = &regs->data[priv->dreg];
	union { u32 u32; u16 u16; } *s, *d;
	unsigned int i;

	s = (void *)src;
	d = (void *)dst;

	switch (priv->size) {
	case 4:
		switch (priv->op) {
		case NFT_BYTEORDER_NTOH:
			for (i = 0; i < priv->len / 4; i++)
				d[i].u32 = ntohl((__force __be32)s[i].u32);
			break;
		case NFT_BYTEORDER_HTON:
			for (i = 0; i < priv->len / 4; i++)
				d[i].u32 = (__force __u32)htonl(s[i].u32);
			break;
		}
		break;
	case 2:
		switch (priv->op) {
		case NFT_BYTEORDER_NTOH:
			for (i = 0; i < priv->len / 2; i++)
				d[i].u16 = ntohs((__force __be16)s[i].u16);
			break;
		case NFT_BYTEORDER_HTON:
			for (i = 0; i < priv->len / 2; i++)
				d[i].u16 = (__force __u16)htons(s[i].u16);
			break;
		}
		break;
	}
}

static const struct nla_policy nft_byteorder_policy[NFTA_BYTEORDER_MAX + 1] = {
	[NFTA_BYTEORDER_SREG]	= { .type = NLA_U32 },
	[NFTA_BYTEORDER_DREG]	= { .type = NLA_U32 },
	[NFTA_BYTEORDER_OP]	= { .type = NLA_U32 },
	[NFTA_BYTEORDER_LEN]	= { .type = NLA_U32 },
	[NFTA_BYTEORDER_SIZE]	= { .type = NLA_U32 },
};

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);
	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;
	}

	priv->size = ntohl(nla_get_be32(tb[NFTA_BYTEORDER_SIZE]));
	switch (priv->size) {
	case 2:
	case 4:
		break;
	default:
		return -EINVAL;
	}

	priv->sreg = nft_parse_register(tb[NFTA_BYTEORDER_SREG]);
	priv->len  = ntohl(nla_get_be32(tb[NFTA_BYTEORDER_LEN]));
	err = nft_validate_register_load(priv->sreg, priv->len);
	if (err < 0)
		return err;

	priv->dreg = nft_parse_register(tb[NFTA_BYTEORDER_DREG]);
	return nft_validate_register_store(ctx, priv->dreg, NULL,
					   NFT_DATA_VALUE, priv->len);
}

static int nft_byteorder_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
	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_LEN, htonl(priv->len)))
		goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_BYTEORDER_SIZE, htonl(priv->size)))
		goto nla_put_failure;
	return 0;

nla_put_failure:
	return -1;
}

static struct nft_expr_type nft_byteorder_type;
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,
};

static 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,
};

int __init nft_byteorder_module_init(void)
{
	return nft_register_expr(&nft_byteorder_type);
}

void nft_byteorder_module_exit(void)
{
	nft_unregister_expr(&nft_byteorder_type);
}