linux/net/netfilter/nft_bitwise.c

// 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/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 <net/netfilter/nf_tables_offload.h>

struct nft_bitwise {
	u8			sreg;
	u8			dreg;
	enum nft_bitwise_ops	op:8;
	u8			len;
	struct nft_data		mask;
	struct nft_data		xor;
	struct nft_data		data;
};

static void nft_bitwise_eval_bool(u32 *dst, const u32 *src,
				  const struct nft_bitwise *priv)
{
	unsigned int i;

	for (i = 0; i < DIV_ROUND_UP(priv->len, sizeof(u32)); i++)
		dst[i] = (src[i] & priv->mask.data[i]) ^ priv->xor.data[i];
}

static void nft_bitwise_eval_lshift(u32 *dst, const u32 *src,
				    const struct nft_bitwise *priv)
{
	u32 shift = priv->data.data[0];
	unsigned int i;
	u32 carry = 0;

	for (i = DIV_ROUND_UP(priv->len, sizeof(u32)); i > 0; i--) {
		dst[i - 1] = (src[i - 1] << shift) | carry;
		carry = src[i - 1] >> (BITS_PER_TYPE(u32) - shift);
	}
}

static void nft_bitwise_eval_rshift(u32 *dst, const u32 *src,
				    const struct nft_bitwise *priv)
{
	u32 shift = priv->data.data[0];
	unsigned int i;
	u32 carry = 0;

	for (i = 0; i < DIV_ROUND_UP(priv->len, sizeof(u32)); i++) {
		dst[i] = carry | (src[i] >> shift);
		carry = src[i] << (BITS_PER_TYPE(u32) - shift);
	}
}

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

	switch (priv->op) {
	case NFT_BITWISE_BOOL:
		nft_bitwise_eval_bool(dst, src, priv);
		break;
	case NFT_BITWISE_LSHIFT:
		nft_bitwise_eval_lshift(dst, src, priv);
		break;
	case NFT_BITWISE_RSHIFT:
		nft_bitwise_eval_rshift(dst, src, priv);
		break;
	}
}

static const struct nla_policy nft_bitwise_policy[NFTA_BITWISE_MAX + 1] = {
	[NFTA_BITWISE_SREG]	= { .type = NLA_U32 },
	[NFTA_BITWISE_DREG]	= { .type = NLA_U32 },
	[NFTA_BITWISE_LEN]	= { .type = NLA_U32 },
	[NFTA_BITWISE_MASK]	= { .type = NLA_NESTED },
	[NFTA_BITWISE_XOR]	= { .type = NLA_NESTED },
	[NFTA_BITWISE_OP]	= NLA_POLICY_MAX(NLA_BE32, 255),
	[NFTA_BITWISE_DATA]	= { .type = NLA_NESTED },
};

static int nft_bitwise_init_bool(struct nft_bitwise *priv,
				 const struct nlattr *const tb[])
{
	struct nft_data_desc mask = {
		.type	= NFT_DATA_VALUE,
		.size	= sizeof(priv->mask),
		.len	= priv->len,
	};
	struct nft_data_desc xor = {
		.type	= NFT_DATA_VALUE,
		.size	= sizeof(priv->xor),
		.len	= priv->len,
	};
	int err;

	if (tb[NFTA_BITWISE_DATA])
		return -EINVAL;

	if (!tb[NFTA_BITWISE_MASK] ||
	    !tb[NFTA_BITWISE_XOR])
		return -EINVAL;

	err = nft_data_init(NULL, &priv->mask, &mask, tb[NFTA_BITWISE_MASK]);
	if (err < 0)
		return err;

	err = nft_data_init(NULL, &priv->xor, &xor, tb[NFTA_BITWISE_XOR]);
	if (err < 0)
		goto err_xor_err;

	return 0;

err_xor_err:
	nft_data_release(&priv->mask, mask.type);

	return err;
}

static int nft_bitwise_init_shift(struct nft_bitwise *priv,
				  const struct nlattr *const tb[])
{
	struct nft_data_desc desc = {
		.type	= NFT_DATA_VALUE,
		.size	= sizeof(priv->data),
		.len	= sizeof(u32),
	};
	int err;

	if (tb[NFTA_BITWISE_MASK] ||
	    tb[NFTA_BITWISE_XOR])
		return -EINVAL;

	if (!tb[NFTA_BITWISE_DATA])
		return -EINVAL;

	err = nft_data_init(NULL, &priv->data, &desc, tb[NFTA_BITWISE_DATA]);
	if (err < 0)
		return err;

	if (priv->data.data[0] >= BITS_PER_TYPE(u32)) {
		nft_data_release(&priv->data, desc.type);
		return -EINVAL;
	}

	return 0;
}

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

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

	priv->len = len;

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

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

	if (tb[NFTA_BITWISE_OP]) {
		priv->op = ntohl(nla_get_be32(tb[NFTA_BITWISE_OP]));
		switch (priv->op) {
		case NFT_BITWISE_BOOL:
		case NFT_BITWISE_LSHIFT:
		case NFT_BITWISE_RSHIFT:
			break;
		default:
			return -EOPNOTSUPP;
		}
	} else {
		priv->op = NFT_BITWISE_BOOL;
	}

	switch(priv->op) {
	case NFT_BITWISE_BOOL:
		err = nft_bitwise_init_bool(priv, tb);
		break;
	case NFT_BITWISE_LSHIFT:
	case NFT_BITWISE_RSHIFT:
		err = nft_bitwise_init_shift(priv, tb);
		break;
	}

	return err;
}

static int nft_bitwise_dump_bool(struct sk_buff *skb,
				 const struct nft_bitwise *priv)
{
	if (nft_data_dump(skb, NFTA_BITWISE_MASK, &priv->mask,
			  NFT_DATA_VALUE, priv->len) < 0)
		return -1;

	if (nft_data_dump(skb, NFTA_BITWISE_XOR, &priv->xor,
			  NFT_DATA_VALUE, priv->len) < 0)
		return -1;

	return 0;
}

static int nft_bitwise_dump_shift(struct sk_buff *skb,
				  const struct nft_bitwise *priv)
{
	if (nft_data_dump(skb, NFTA_BITWISE_DATA, &priv->data,
			  NFT_DATA_VALUE, sizeof(u32)) < 0)
		return -1;
	return 0;
}

static int nft_bitwise_dump(struct sk_buff *skb,
			    const struct nft_expr *expr, bool reset)
{
	const struct nft_bitwise *priv = nft_expr_priv(expr);
	int err = 0;

	if (nft_dump_register(skb, NFTA_BITWISE_SREG, priv->sreg))
		return -1;
	if (nft_dump_register(skb, NFTA_BITWISE_DREG, priv->dreg))
		return -1;
	if (nla_put_be32(skb, NFTA_BITWISE_LEN, htonl(priv->len)))
		return -1;
	if (nla_put_be32(skb, NFTA_BITWISE_OP, htonl(priv->op)))
		return -1;

	switch (priv->op) {
	case NFT_BITWISE_BOOL:
		err = nft_bitwise_dump_bool(skb, priv);
		break;
	case NFT_BITWISE_LSHIFT:
	case NFT_BITWISE_RSHIFT:
		err = nft_bitwise_dump_shift(skb, priv);
		break;
	}

	return err;
}

static struct nft_data zero;

static int nft_bitwise_offload(struct nft_offload_ctx *ctx,
			       struct nft_flow_rule *flow,
			       const struct nft_expr *expr)
{
	const struct nft_bitwise *priv = nft_expr_priv(expr);
	struct nft_offload_reg *reg = &ctx->regs[priv->dreg];

	if (priv->op != NFT_BITWISE_BOOL)
		return -EOPNOTSUPP;

	if (memcmp(&priv->xor, &zero, sizeof(priv->xor)) ||
	    priv->sreg != priv->dreg || priv->len != reg->len)
		return -EOPNOTSUPP;

	memcpy(&reg->mask, &priv->mask, sizeof(priv->mask));

	return 0;
}

static bool nft_bitwise_reduce(struct nft_regs_track *track,
			       const struct nft_expr *expr)
{
	const struct nft_bitwise *priv = nft_expr_priv(expr);
	const struct nft_bitwise *bitwise;
	unsigned int regcount;
	u8 dreg;
	int i;

	if (!track->regs[priv->sreg].selector)
		return false;

	bitwise = nft_expr_priv(track->regs[priv->dreg].selector);
	if (track->regs[priv->sreg].selector == track->regs[priv->dreg].selector &&
	    track->regs[priv->sreg].num_reg == 0 &&
	    track->regs[priv->dreg].bitwise &&
	    track->regs[priv->dreg].bitwise->ops == expr->ops &&
	    priv->sreg == bitwise->sreg &&
	    priv->dreg == bitwise->dreg &&
	    priv->op == bitwise->op &&
	    priv->len == bitwise->len &&
	    !memcmp(&priv->mask, &bitwise->mask, sizeof(priv->mask)) &&
	    !memcmp(&priv->xor, &bitwise->xor, sizeof(priv->xor)) &&
	    !memcmp(&priv->data, &bitwise->data, sizeof(priv->data))) {
		track->cur = expr;
		return true;
	}

	if (track->regs[priv->sreg].bitwise ||
	    track->regs[priv->sreg].num_reg != 0) {
		nft_reg_track_cancel(track, priv->dreg, priv->len);
		return false;
	}

	if (priv->sreg != priv->dreg) {
		nft_reg_track_update(track, track->regs[priv->sreg].selector,
				     priv->dreg, priv->len);
	}

	dreg = priv->dreg;
	regcount = DIV_ROUND_UP(priv->len, NFT_REG32_SIZE);
	for (i = 0; i < regcount; i++, dreg++)
		track->regs[dreg].bitwise = expr;

	return false;
}

static const struct nft_expr_ops nft_bitwise_ops = {
	.type		= &nft_bitwise_type,
	.size		= NFT_EXPR_SIZE(sizeof(struct nft_bitwise)),
	.eval		= nft_bitwise_eval,
	.init		= nft_bitwise_init,
	.dump		= nft_bitwise_dump,
	.reduce		= nft_bitwise_reduce,
	.offload	= nft_bitwise_offload,
};

static int
nft_bitwise_extract_u32_data(const struct nlattr * const tb, u32 *out)
{
	struct nft_data data;
	struct nft_data_desc desc = {
		.type	= NFT_DATA_VALUE,
		.size	= sizeof(data),
		.len	= sizeof(u32),
	};
	int err;

	err = nft_data_init(NULL, &data, &desc, tb);
	if (err < 0)
		return err;

	*out = data.data[0];

	return 0;
}

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

	err = nft_parse_register_load(tb[NFTA_BITWISE_SREG], &priv->sreg,
				      sizeof(u32));
	if (err < 0)
		return err;

	err = nft_parse_register_store(ctx, tb[NFTA_BITWISE_DREG], &priv->dreg,
				       NULL, NFT_DATA_VALUE, sizeof(u32));
	if (err < 0)
		return err;

	if (tb[NFTA_BITWISE_DATA])
		return -EINVAL;

	if (!tb[NFTA_BITWISE_MASK] ||
	    !tb[NFTA_BITWISE_XOR])
		return -EINVAL;

	err = nft_bitwise_extract_u32_data(tb[NFTA_BITWISE_MASK], &priv->mask);
	if (err < 0)
		return err;

	err = nft_bitwise_extract_u32_data(tb[NFTA_BITWISE_XOR], &priv->xor);
	if (err < 0)
		return err;

	return 0;
}

static int
nft_bitwise_fast_dump(struct sk_buff *skb,
		      const struct nft_expr *expr, bool reset)
{
	const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
	struct nft_data data;

	if (nft_dump_register(skb, NFTA_BITWISE_SREG, priv->sreg))
		return -1;
	if (nft_dump_register(skb, NFTA_BITWISE_DREG, priv->dreg))
		return -1;
	if (nla_put_be32(skb, NFTA_BITWISE_LEN, htonl(sizeof(u32))))
		return -1;
	if (nla_put_be32(skb, NFTA_BITWISE_OP, htonl(NFT_BITWISE_BOOL)))
		return -1;

	data.data[0] = priv->mask;
	if (nft_data_dump(skb, NFTA_BITWISE_MASK, &data,
			  NFT_DATA_VALUE, sizeof(u32)) < 0)
		return -1;

	data.data[0] = priv->xor;
	if (nft_data_dump(skb, NFTA_BITWISE_XOR, &data,
			  NFT_DATA_VALUE, sizeof(u32)) < 0)
		return -1;

	return 0;
}

static int nft_bitwise_fast_offload(struct nft_offload_ctx *ctx,
				    struct nft_flow_rule *flow,
				    const struct nft_expr *expr)
{
	const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
	struct nft_offload_reg *reg = &ctx->regs[priv->dreg];

	if (priv->xor || priv->sreg != priv->dreg || reg->len != sizeof(u32))
		return -EOPNOTSUPP;

	reg->mask.data[0] = priv->mask;
	return 0;
}

static bool nft_bitwise_fast_reduce(struct nft_regs_track *track,
				    const struct nft_expr *expr)
{
	const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);
	const struct nft_bitwise_fast_expr *bitwise;

	if (!track->regs[priv->sreg].selector)
		return false;

	bitwise = nft_expr_priv(track->regs[priv->dreg].selector);
	if (track->regs[priv->sreg].selector == track->regs[priv->dreg].selector &&
	    track->regs[priv->dreg].bitwise &&
	    track->regs[priv->dreg].bitwise->ops == expr->ops &&
	    priv->sreg == bitwise->sreg &&
	    priv->dreg == bitwise->dreg &&
	    priv->mask == bitwise->mask &&
	    priv->xor == bitwise->xor) {
		track->cur = expr;
		return true;
	}

	if (track->regs[priv->sreg].bitwise) {
		nft_reg_track_cancel(track, priv->dreg, NFT_REG32_SIZE);
		return false;
	}

	if (priv->sreg != priv->dreg) {
		track->regs[priv->dreg].selector =
			track->regs[priv->sreg].selector;
	}
	track->regs[priv->dreg].bitwise = expr;

	return false;
}

const struct nft_expr_ops nft_bitwise_fast_ops = {
	.type		= &nft_bitwise_type,
	.size		= NFT_EXPR_SIZE(sizeof(struct nft_bitwise_fast_expr)),
	.eval		= NULL, /* inlined */
	.init		= nft_bitwise_fast_init,
	.dump		= nft_bitwise_fast_dump,
	.reduce		= nft_bitwise_fast_reduce,
	.offload	= nft_bitwise_fast_offload,
};

static const struct nft_expr_ops *
nft_bitwise_select_ops(const struct nft_ctx *ctx,
		       const struct nlattr * const tb[])
{
	int err;
	u32 len;

	if (!tb[NFTA_BITWISE_LEN] ||
	    !tb[NFTA_BITWISE_SREG] ||
	    !tb[NFTA_BITWISE_DREG])
		return ERR_PTR(-EINVAL);

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

	if (len != sizeof(u32))
		return &nft_bitwise_ops;

	if (tb[NFTA_BITWISE_OP] &&
	    ntohl(nla_get_be32(tb[NFTA_BITWISE_OP])) != NFT_BITWISE_BOOL)
		return &nft_bitwise_ops;

	return &nft_bitwise_fast_ops;
}

struct nft_expr_type nft_bitwise_type __read_mostly = {
	.name		= "bitwise",
	.select_ops	= nft_bitwise_select_ops,
	.policy		= nft_bitwise_policy,
	.maxattr	= NFTA_BITWISE_MAX,
	.owner		= THIS_MODULE,
};

bool nft_expr_reduce_bitwise(struct nft_regs_track *track,
			     const struct nft_expr *expr)
{
	const struct nft_expr *last = track->last;
	const struct nft_expr *next;

	if (expr == last)
		return false;

	next = nft_expr_next(expr);
	if (next->ops == &nft_bitwise_ops)
		return nft_bitwise_reduce(track, next);
	else if (next->ops == &nft_bitwise_fast_ops)
		return nft_bitwise_fast_reduce(track, next);

	return false;
}
EXPORT_SYMBOL_GPL(nft_expr_reduce_bitwise);