xref: /Linux-v4.19/net/netfilter/nf_tables_core.c

/*
 * Copyright (c) 2008 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/module.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/static_key.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_core.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_log.h>

static noinline void __nft_trace_packet(struct nft_traceinfo *info,
					const struct nft_chain *chain,
					enum nft_trace_types type)
{
	const struct nft_pktinfo *pkt = info->pkt;

	if (!info->trace || !pkt->skb->nf_trace)
		return;

	info->chain = chain;
	info->type = type;

	nft_trace_notify(info);
}

static inline void nft_trace_packet(struct nft_traceinfo *info,
				    const struct nft_chain *chain,
				    const struct nft_rule *rule,
				    enum nft_trace_types type)
{
	if (static_branch_unlikely(&nft_trace_enabled)) {
		info->rule = rule;
		__nft_trace_packet(info, chain, type);
	}
}

static void nft_cmp_fast_eval(const struct nft_expr *expr,
			      struct nft_regs *regs)
{
	const struct nft_cmp_fast_expr *priv = nft_expr_priv(expr);
	u32 mask = nft_cmp_fast_mask(priv->len);

	if ((regs->data[priv->sreg] & mask) == priv->data)
		return;
	regs->verdict.code = NFT_BREAK;
}

static bool nft_payload_fast_eval(const struct nft_expr *expr,
				  struct nft_regs *regs,
				  const struct nft_pktinfo *pkt)
{
	const struct nft_payload *priv = nft_expr_priv(expr);
	const struct sk_buff *skb = pkt->skb;
	u32 *dest = &regs->data[priv->dreg];
	unsigned char *ptr;

	if (priv->base == NFT_PAYLOAD_NETWORK_HEADER)
		ptr = skb_network_header(skb);
	else {
		if (!pkt->tprot_set)
			return false;
		ptr = skb_network_header(skb) + pkt->xt.thoff;
	}

	ptr += priv->offset;

	if (unlikely(ptr + priv->len > skb_tail_pointer(skb)))
		return false;

	*dest = 0;
	if (priv->len == 2)
		*(u16 *)dest = *(u16 *)ptr;
	else if (priv->len == 4)
		*(u32 *)dest = *(u32 *)ptr;
	else
		*(u8 *)dest = *(u8 *)ptr;
	return true;
}

DEFINE_STATIC_KEY_FALSE(nft_counters_enabled);

static noinline void nft_update_chain_stats(const struct nft_chain *chain,
					    const struct nft_pktinfo *pkt)
{
	struct nft_base_chain *base_chain;
	struct nft_stats *stats;

	base_chain = nft_base_chain(chain);
	if (!base_chain->stats)
		return;

	local_bh_disable();
	stats = this_cpu_ptr(rcu_dereference(base_chain->stats));
	if (stats) {
		u64_stats_update_begin(&stats->syncp);
		stats->pkts++;
		stats->bytes += pkt->skb->len;
		u64_stats_update_end(&stats->syncp);
	}
	local_bh_enable();
}

struct nft_jumpstack {
	const struct nft_chain	*chain;
	struct nft_rule	*const *rules;
};

static void expr_call_ops_eval(const struct nft_expr *expr,
			       struct nft_regs *regs,
			       struct nft_pktinfo *pkt)
{
	unsigned long e = (unsigned long)expr->ops->eval;

	if (e == (unsigned long)nft_meta_get_eval)
		nft_meta_get_eval(expr, regs, pkt);
	else if (e == (unsigned long)nft_lookup_eval)
		nft_lookup_eval(expr, regs, pkt);
	else
		expr->ops->eval(expr, regs, pkt);
}

unsigned int
nft_do_chain(struct nft_pktinfo *pkt, void *priv)
{
	const struct nft_chain *chain = priv, *basechain = chain;
	const struct net *net = nft_net(pkt);
	struct nft_rule *const *rules;
	const struct nft_rule *rule;
	const struct nft_expr *expr, *last;
	struct nft_regs regs;
	unsigned int stackptr = 0;
	struct nft_jumpstack jumpstack[NFT_JUMP_STACK_SIZE];
	bool genbit = READ_ONCE(net->nft.gencursor);
	struct nft_traceinfo info;

	info.trace = false;
	if (static_branch_unlikely(&nft_trace_enabled))
		nft_trace_init(&info, pkt, &regs.verdict, basechain);
do_chain:
	if (genbit)
		rules = rcu_dereference(chain->rules_gen_1);
	else
		rules = rcu_dereference(chain->rules_gen_0);

next_rule:
	rule = *rules;
	regs.verdict.code = NFT_CONTINUE;
	for (; *rules ; rules++) {
		rule = *rules;
		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_payload_fast_ops ||
				 !nft_payload_fast_eval(expr, &regs, pkt))
				expr_call_ops_eval(expr, &regs, pkt);

			if (regs.verdict.code != NFT_CONTINUE)
				break;
		}

		switch (regs.verdict.code) {
		case NFT_BREAK:
			regs.verdict.code = NFT_CONTINUE;
			continue;
		case NFT_CONTINUE:
			nft_trace_packet(&info, chain, rule,
					 NFT_TRACETYPE_RULE);
			continue;
		}
		break;
	}

	switch (regs.verdict.code & NF_VERDICT_MASK) {
	case NF_ACCEPT:
	case NF_DROP:
	case NF_QUEUE:
	case NF_STOLEN:
		nft_trace_packet(&info, chain, rule,
				 NFT_TRACETYPE_RULE);
		return regs.verdict.code;
	}

	switch (regs.verdict.code) {
	case NFT_JUMP:
		if (WARN_ON_ONCE(stackptr >= NFT_JUMP_STACK_SIZE))
			return NF_DROP;
		jumpstack[stackptr].chain = chain;
		jumpstack[stackptr].rules = rules + 1;
		stackptr++;
		/* fall through */
	case NFT_GOTO:
		nft_trace_packet(&info, chain, rule,
				 NFT_TRACETYPE_RULE);

		chain = regs.verdict.chain;
		goto do_chain;
	case NFT_CONTINUE:
		/* fall through */
	case NFT_RETURN:
		nft_trace_packet(&info, chain, rule,
				 NFT_TRACETYPE_RETURN);
		break;
	default:
		WARN_ON(1);
	}

	if (stackptr > 0) {
		stackptr--;
		chain = jumpstack[stackptr].chain;
		rules = jumpstack[stackptr].rules;
		goto next_rule;
	}

	nft_trace_packet(&info, basechain, NULL, NFT_TRACETYPE_POLICY);

	if (static_branch_unlikely(&nft_counters_enabled))
		nft_update_chain_stats(basechain, pkt);

	return nft_base_chain(basechain)->policy;
}
EXPORT_SYMBOL_GPL(nft_do_chain);

static struct nft_expr_type *nft_basic_types[] = {
	&nft_imm_type,
	&nft_cmp_type,
	&nft_lookup_type,
	&nft_bitwise_type,
	&nft_byteorder_type,
	&nft_payload_type,
	&nft_dynset_type,
	&nft_range_type,
	&nft_meta_type,
	&nft_rt_type,
	&nft_exthdr_type,
};

int __init nf_tables_core_module_init(void)
{
	int err, i;

	for (i = 0; i < ARRAY_SIZE(nft_basic_types); i++) {
		err = nft_register_expr(nft_basic_types[i]);
		if (err)
			goto err;
	}

	return 0;

err:
	while (i-- > 0)
		nft_unregister_expr(nft_basic_types[i]);
	return err;
}

void nf_tables_core_module_exit(void)
{
	int i;

	i = ARRAY_SIZE(nft_basic_types);
	while (i-- > 0)
		nft_unregister_expr(nft_basic_types[i]);
}