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netfilter: nft_limit: convert to token-based limiting at nanosecond granularity

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Rework the limit expression to use a token-based limiting approach that refills
the bucket gradually. The tokens are calculated at nanosecond granularity
instead jiffies to improve precision.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2015-07-31 14:10:22 +02:00
parent 09e4e42a00
commit dba27ec1bc
1 changed files with 25 additions and 15 deletions
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40
net/netfilter/nft_limit.c
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@ -20,10 +20,11 @@
static DEFINE_SPINLOCK(limit_lock);
struct nft_limit {
u64 last;
u64 tokens;
u64 tokens_max;
u64 rate;
u64 unit;
unsigned long stamp;
u64 nsecs;
};
static void nft_limit_pkts_eval(const struct nft_expr *expr,
@ -31,18 +32,23 @@ static void nft_limit_pkts_eval(const struct nft_expr *expr,
const struct nft_pktinfo *pkt)
{
struct nft_limit *priv = nft_expr_priv(expr);
u64 now, tokens, cost = div_u64(priv->nsecs, priv->rate);
s64 delta;
spin_lock_bh(&limit_lock);
if (time_after_eq(jiffies, priv->stamp)) {
priv->tokens = priv->rate;
priv->stamp = jiffies + priv->unit * HZ;
}
now = ktime_get_ns();
tokens = priv->tokens + now - priv->last;
if (tokens > priv->tokens_max)
tokens = priv->tokens_max;
if (priv->tokens >= 1) {
priv->tokens--;
priv->last = now;
delta = tokens - cost;
if (delta >= 0) {
priv->tokens = delta;
spin_unlock_bh(&limit_lock);
return;
}
priv->tokens = tokens;
spin_unlock_bh(&limit_lock);
regs->verdict.code = NFT_BREAK;
@ -58,25 +64,29 @@ static int nft_limit_init(const struct nft_ctx *ctx,
const struct nlattr * const tb[])
{
struct nft_limit *priv = nft_expr_priv(expr);
u64 unit;
if (tb[NFTA_LIMIT_RATE] == NULL ||
tb[NFTA_LIMIT_UNIT] == NULL)
return -EINVAL;
priv->rate = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_RATE]));
priv->unit = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_UNIT]));
priv->stamp = jiffies + priv->unit * HZ;
priv->tokens = priv->rate;
priv->rate = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_RATE]));
unit = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_UNIT]));
priv->nsecs = unit * NSEC_PER_SEC;
if (priv->rate == 0 || priv->nsecs < unit)
return -EOVERFLOW;
priv->tokens = priv->tokens_max = priv->nsecs;
priv->last = ktime_get_ns();
return 0;
}
static int nft_limit_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
const struct nft_limit *priv = nft_expr_priv(expr);
u64 secs = div_u64(priv->nsecs, NSEC_PER_SEC);
if (nla_put_be64(skb, NFTA_LIMIT_RATE, cpu_to_be64(priv->rate)))
goto nla_put_failure;
if (nla_put_be64(skb, NFTA_LIMIT_UNIT, cpu_to_be64(priv->unit)))
if (nla_put_be64(skb, NFTA_LIMIT_RATE, cpu_to_be64(priv->rate)) ||
nla_put_be64(skb, NFTA_LIMIT_UNIT, cpu_to_be64(secs)))
goto nla_put_failure;
return 0;