Commit 10fdd6d8 authored by Phil Sutter's avatar Phil Sutter Committed by Pablo Neira Ayuso
Browse files

netfilter: nf_tables: Implement fast bitwise expression 



A typical use of bitwise expression is to mask out parts of an IP
address when matching on the network part only. Optimize for this common
use with a fast variant for NFT_BITWISE_BOOL-type expressions operating
on 32bit-sized values.

Signed-off-by: default avatarPhil Sutter <phil@nwl.cc>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 5f48846d

include/net/netfilter/nf_tables_core.h

+9 −0
Original line number Diff line number Diff line
@@ -23,6 +23,13 @@ extern struct nft_object_type nft_secmark_obj_type; 
int nf_tables_core_module_init(void);

void nf_tables_core_module_exit(void);



struct nft_bitwise_fast_expr {

	u32			mask;

	u32			xor;

	enum nft_registers	sreg:8;

	enum nft_registers	dreg:8;

};



struct nft_cmp_fast_expr {

	u32			data;

	u32			mask;
@@ -68,6 +75,8 @@ struct nft_payload_set { 


extern const struct nft_expr_ops nft_payload_fast_ops;



extern const struct nft_expr_ops nft_bitwise_fast_ops;



extern struct static_key_false nft_counters_enabled;

extern struct static_key_false nft_trace_enabled;

net/netfilter/nf_tables_core.c

+12 −0
Original line number Diff line number Diff line
@@ -47,6 +47,16 @@ static inline void nft_trace_packet(struct nft_traceinfo *info, 
	}

}



static void nft_bitwise_fast_eval(const struct nft_expr *expr,

				  struct nft_regs *regs)

{

	const struct nft_bitwise_fast_expr *priv = nft_expr_priv(expr);

	u32 *src = &regs->data[priv->sreg];

	u32 *dst = &regs->data[priv->dreg];



	*dst = (*src & priv->mask) ^ priv->xor;

}



static void nft_cmp_fast_eval(const struct nft_expr *expr,

			      struct nft_regs *regs)

{
@@ -175,6 +185,8 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv) 
		nft_rule_for_each_expr(expr, last, rule) {

			if (expr->ops == &nft_cmp_fast_ops)

				nft_cmp_fast_eval(expr, &regs);

			else if (expr->ops == &nft_bitwise_fast_ops)

				nft_bitwise_fast_eval(expr, &regs);

			else if (expr->ops != &nft_payload_fast_ops ||

				 !nft_payload_fast_eval(expr, &regs, pkt))

				expr_call_ops_eval(expr, &regs, pkt);

net/netfilter/nft_bitwise.c

+135 −6
Original line number Diff line number Diff line
@@ -163,11 +163,6 @@ static int nft_bitwise_init(const struct nft_ctx *ctx, 
	u32 len;

	int err;



	if (!tb[NFTA_BITWISE_SREG] ||

	    !tb[NFTA_BITWISE_DREG] ||

	    !tb[NFTA_BITWISE_LEN])

		return -EINVAL;



	err = nft_parse_u32_check(tb[NFTA_BITWISE_LEN], U8_MAX, &len);

	if (err < 0)

		return err;
@@ -292,9 +287,143 @@ static const struct nft_expr_ops nft_bitwise_ops = { 
	.offload	= nft_bitwise_offload,

};



static int

nft_bitwise_extract_u32_data(const struct nlattr * const tb, u32 *out)

{

	struct nft_data_desc desc;

	struct nft_data data;

	int err = 0;



	err = nft_data_init(NULL, &data, sizeof(data), &desc, tb);

	if (err < 0)

		return err;



	if (desc.type != NFT_DATA_VALUE || desc.len != sizeof(u32)) {

		err = -EINVAL;

		goto err;

	}

	*out = data.data[0];

err:

	nft_data_release(&data, desc.type);

	return err;

}



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;



	priv->sreg = nft_parse_register(tb[NFTA_BITWISE_SREG]);

	err = nft_validate_register_load(priv->sreg, sizeof(u32));

	if (err < 0)

		return err;



	priv->dreg = nft_parse_register(tb[NFTA_BITWISE_DREG]);

	err = nft_validate_register_store(ctx, 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)

{

	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;

}



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,

	.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",

	.ops		= &nft_bitwise_ops,

	.select_ops	= nft_bitwise_select_ops,

	.policy		= nft_bitwise_policy,

	.maxattr	= NFTA_BITWISE_MAX,

	.owner		= THIS_MODULE,