text: // 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/spinlock.h>
  #include <linux/netlink.h>
  #include <linux/netfilter.h>
  #include <linux/netfilter/nf_tables.h>
  #include <net/netfilter/nf_tables.h>
  
  struct nft_limit {
  	spinlock_t	lock;
  	u64		last;
  	u64		tokens;
  	u64		tokens_max;
  	u64		rate;
  	u64		nsecs;
  	u32		burst;
  	bool		invert;
  };
  
  static inline bool nft_limit_eval(struct nft_limit *limit, u64 cost)
  {
  	u64 now, tokens;
  	s64 delta;
  
  	spin_lock_bh(&limit->lock);
  	now = ktime_get_ns();
  	tokens = limit->tokens + now - limit->last;
  	if (tokens > limit->tokens_max)
  		tokens = limit->tokens_max;
  
  	limit->last = now;
  	delta = tokens - cost;
  	if (delta >= 0) {
  		limit->tokens = delta;
  		spin_unlock_bh(&limit->lock);
  		return limit->invert;
  	}
  	limit->tokens = tokens;
  	spin_unlock_bh(&limit->lock);
  	return !limit->invert;
  }
  
  /* Use same default as in iptables. */
  #define NFT_LIMIT_PKT_BURST_DEFAULT	5
  
  static int nft_limit_init(struct nft_limit *limit,
  			  const struct nlattr * const tb[], bool pkts)
  {
  	u64 unit, tokens;
  
  	if (tb[NFTA_LIMIT_RATE] == NULL ||
  	    tb[NFTA_LIMIT_UNIT] == NULL)
  		return -EINVAL;
  
  	limit->rate = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_RATE]));
  	unit = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_UNIT]));
  	limit->nsecs = unit * NSEC_PER_SEC;
  	if (limit->rate == 0 || limit->nsecs < unit)
  		return -EOVERFLOW;
  
  	if (tb[NFTA_LIMIT_BURST])
  		limit->burst = ntohl(nla_get_be32(tb[NFTA_LIMIT_BURST]));
  
  	if (pkts && limit->burst == 0)
  		limit->burst = NFT_LIMIT_PKT_BURST_DEFAULT;
  
  	if (limit->rate + limit->burst < limit->rate)
  		return -EOVERFLOW;
  
  	if (pkts) {
  		tokens = div_u64(limit->nsecs, limit->rate) * limit->burst;
  	} else {
  		/* The token bucket size limits the number of tokens can be
  		 * accumulated. tokens_max specifies the bucket size.
  		 * tokens_max = unit * (rate + burst) / rate.
  		 */
  		tokens = div_u64(limit->nsecs * (limit->rate + limit->burst),
  				 limit->rate);
  	}
  
  	limit->tokens = tokens;
  	limit->tokens_max = limit->tokens;
  
  	if (tb[NFTA_LIMIT_FLAGS]) {
  		u32 flags = ntohl(nla_get_be32(tb[NFTA_LIMIT_FLAGS]));
  
  		if (flags & NFT_LIMIT_F_INV)
  			limit->invert = true;
  	}
  	limit->last = ktime_get_ns();
  	spin_lock_init(&limit->lock);
  
  	return 0;
  }
  
  static int nft_limit_dump(struct sk_buff *skb, const struct nft_limit *limit,
  			  enum nft_limit_type type)
  {
  	u32 flags = limit->invert ? NFT_LIMIT_F_INV : 0;
  	u64 secs = div_u64(limit->nsecs, NSEC_PER_SEC);
  
  	if (nla_put_be64(skb, NFTA_LIMIT_RATE, cpu_to_be64(limit->rate),
  			 NFTA_LIMIT_PAD) ||
  	    nla_put_be64(skb, NFTA_LIMIT_UNIT, cpu_to_be64(secs),
  			 NFTA_LIMIT_PAD) ||
  	    nla_put_be32(skb, NFTA_LIMIT_BURST, htonl(limit->burst)) ||
  	    nla_put_be32(skb, NFTA_LIMIT_TYPE, htonl(type)) ||
  	    nla_put_be32(skb, NFTA_LIMIT_FLAGS, htonl(flags)))
  		goto nla_put_failure;
  	return 0;
  
  nla_put_failure:
  	return -1;
  }
  
  struct nft_limit_pkts {
  	struct nft_limit	limit;
  	u64			cost;
  };
  
  static void nft_limit_pkts_eval(const struct nft_expr *expr,
  				struct nft_regs *regs,
  				const struct nft_pktinfo *pkt)
  {
  	struct nft_limit_pkts *priv = nft_expr_priv(expr);
  
  	if (nft_limit_eval(&priv->limit, priv->cost))
  		regs->verdict.code = NFT_BREAK;
  }
  
  static const struct nla_policy nft_limit_policy[NFTA_LIMIT_MAX + 1] = {
  	[NFTA_LIMIT_RATE]	= { .type = NLA_U64 },
  	[NFTA_LIMIT_UNIT]	= { .type = NLA_U64 },
  	[NFTA_LIMIT_BURST]	= { .type = NLA_U32 },
  	[NFTA_LIMIT_TYPE]	= { .type = NLA_U32 },
  	[NFTA_LIMIT_FLAGS]	= { .type = NLA_U32 },
  };
  
  static int nft_limit_pkts_init(const struct nft_ctx *ctx,
  			       const struct nft_expr *expr,
  			       const struct nlattr * const tb[])
  {
  	struct nft_limit_pkts *priv = nft_expr_priv(expr);
  	int err;
  
  	err = nft_limit_init(&priv->limit, tb, true);
  	if (err < 0)
  		return err;
  
  	priv->cost = div64_u64(priv->limit.nsecs, priv->limit.rate);
  	return 0;
  }
  
  static int nft_limit_pkts_dump(struct sk_buff *skb, const struct nft_expr *expr)
  {
  	const struct nft_limit_pkts *priv = nft_expr_priv(expr);
  
  	return nft_limit_dump(skb, &priv->limit, NFT_LIMIT_PKTS);
  }
  
  static struct nft_expr_type nft_limit_type;
  static const struct nft_expr_ops nft_limit_pkts_ops = {
  	.type		= &nft_limit_type,
  	.size		= NFT_EXPR_SIZE(sizeof(struct nft_limit_pkts)),
  	.eval		= nft_limit_pkts_eval,
  	.init		= nft_limit_pkts_init,
  	.dump		= nft_limit_pkts_dump,
  };
  
  static void nft_limit_bytes_eval(const struct nft_expr *expr,
  				 struct nft_regs *regs,
  				 const struct nft_pktinfo *pkt)
  {
  	struct nft_limit *priv = nft_expr_priv(expr);
  	u64 cost = div64_u64(priv->nsecs * pkt->skb->len, priv->rate);
  
  	if (nft_limit_eval(priv, cost))
  		regs->verdict.code = NFT_BREAK;
  }
  
  static int nft_limit_bytes_init(const struct nft_ctx *ctx,
  				const struct nft_expr *expr,
  				const struct nlattr * const tb[])
  {
  	struct nft_limit *priv = nft_expr_priv(expr);
  
  	return nft_limit_init(priv, tb, false);
  }
  
  static int nft_limit_bytes_dump(struct sk_buff *skb,
  				const struct nft_expr *expr)
  {
  	const struct nft_limit *priv = nft_expr_priv(expr);
  
  	return nft_limit_dump(skb, priv, NFT_LIMIT_PKT_BYTES);
  }
  
  static const struct nft_expr_ops nft_limit_bytes_ops = {
  	.type		= &nft_limit_type,
  	.size		= NFT_EXPR_SIZE(sizeof(struct nft_limit)),
  	.eval		= nft_limit_bytes_eval,
  	.init		= nft_limit_bytes_init,
  	.dump		= nft_limit_bytes_dump,
  };
  
  static const struct nft_expr_ops *
  nft_limit_select_ops(const struct nft_ctx *ctx,
  		     const struct nlattr * const tb[])
  {
  	if (tb[NFTA_LIMIT_TYPE] == NULL)
  		return &nft_limit_pkts_ops;
  
  	switch (ntohl(nla_get_be32(tb[NFTA_LIMIT_TYPE]))) {
  	case NFT_LIMIT_PKTS:
  		return &nft_limit_pkts_ops;
  	case NFT_LIMIT_PKT_BYTES:
  		return &nft_limit_bytes_ops;
  	}
  	return ERR_PTR(-EOPNOTSUPP);
  }
  
  static struct nft_expr_type nft_limit_type __read_mostly = {
  	.name		= "limit",
  	.select_ops	= nft_limit_select_ops,
  	.policy		= nft_limit_policy,
  	.maxattr	= NFTA_LIMIT_MAX,
  	.flags		= NFT_EXPR_STATEFUL,
  	.owner		= THIS_MODULE,
  };
  
  static void nft_limit_obj_pkts_eval(struct nft_object *obj,
  				    struct nft_regs *regs,
  				    const struct nft_pktinfo *pkt)
  {
  	struct nft_limit_pkts *priv = nft_obj_data(obj);
  
  	if (nft_limit_eval(&priv->limit, priv->cost))
  		regs->verdict.code = NFT_BREAK;
  }
  
  static int nft_limit_obj_pkts_init(const struct nft_ctx *ctx,
  				   const struct nlattr * const tb[],
  				   struct nft_object *obj)
  {
  	struct nft_limit_pkts *priv = nft_obj_data(obj);
  	int err;
  
  	err = nft_limit_init(&priv->limit, tb, true);
  	if (err < 0)
  		return err;
  
  	priv->cost = div64_u64(priv->limit.nsecs, priv->limit.rate);
  	return 0;
  }
  
  static int nft_limit_obj_pkts_dump(struct sk_buff *skb,
  				   struct nft_object *obj,
  				   bool reset)
  {
  	const struct nft_limit_pkts *priv = nft_obj_data(obj);
  
  	return nft_limit_dump(skb, &priv->limit, NFT_LIMIT_PKTS);
  }
  
  static struct nft_object_type nft_limit_obj_type;
  static const struct nft_object_ops nft_limit_obj_pkts_ops = {
  	.type		= &nft_limit_obj_type,
  	.size		= NFT_EXPR_SIZE(sizeof(struct nft_limit_pkts)),
  	.init		= nft_limit_obj_pkts_init,
  	.eval		= nft_limit_obj_pkts_eval,
  	.dump		= nft_limit_obj_pkts_dump,
  };
  
  static void nft_limit_obj_bytes_eval(struct nft_object *obj,
  				     struct nft_regs *regs,
  				     const struct nft_pktinfo *pkt)
  {
  	struct nft_limit *priv = nft_obj_data(obj);
  	u64 cost = div64_u64(priv->nsecs * pkt->skb->len, priv->rate);
  
  	if (nft_limit_eval(priv, cost))
  		regs->verdict.code = NFT_BREAK;
  }
  
  static int nft_limit_obj_bytes_init(const struct nft_ctx *ctx,
  				    const struct nlattr * const tb[],
  				    struct nft_object *obj)
  {
  	struct nft_limit *priv = nft_obj_data(obj);
  
  	return nft_limit_init(priv, tb, false);
  }
  
  static int nft_limit_obj_bytes_dump(struct sk_buff *skb,
  				    struct nft_object *obj,
  				    bool reset)
  {
  	const struct nft_limit *priv = nft_obj_data(obj);
  
  	return nft_limit_dump(skb, priv, NFT_LIMIT_PKT_BYTES);
  }
  
  static struct nft_object_type nft_limit_obj_type;
  static const struct nft_object_ops nft_limit_obj_bytes_ops = {
  	.type		= &nft_limit_obj_type,
  	.size		= sizeof(struct nft_limit),
  	.init		= nft_limit_obj_bytes_init,
  	.eval		= nft_limit_obj_bytes_eval,
  	.dump		= nft_limit_obj_bytes_dump,
  };
  
  static const struct nft_object_ops *
  nft_limit_obj_select_ops(const struct nft_ctx *ctx,
  			 const struct nlattr * const tb[])
  {
  	if (!tb[NFTA_LIMIT_TYPE])
  		return &nft_limit_obj_pkts_ops;
  
  	switch (ntohl(nla_get_be32(tb[NFTA_LIMIT_TYPE]))) {
  	case NFT_LIMIT_PKTS:
  		return &nft_limit_obj_pkts_ops;
  	case NFT_LIMIT_PKT_BYTES:
  		return &nft_limit_obj_bytes_ops;
  	}
  	return ERR_PTR(-EOPNOTSUPP);
  }
  
  static struct nft_object_type nft_limit_obj_type __read_mostly = {
  	.select_ops	= nft_limit_obj_select_ops,
  	.type		= NFT_OBJECT_LIMIT,
  	.maxattr	= NFTA_LIMIT_MAX,
  	.policy		= nft_limit_policy,
  	.owner		= THIS_MODULE,
  };
  
  static int __init nft_limit_module_init(void)
  {
  	int err;
  
  	err = nft_register_obj(&nft_limit_obj_type);
  	if (err < 0)
  		return err;
  
  	err = nft_register_expr(&nft_limit_type);
  	if (err < 0)
  		goto err1;
  
  	return 0;
  err1:
  	nft_unregister_obj(&nft_limit_obj_type);
  	return err;
  }
  
  static void __exit nft_limit_module_exit(void)
  {
  	nft_unregister_expr(&nft_limit_type);
  	nft_unregister_obj(&nft_limit_obj_type);
  }
  
  module_init(nft_limit_module_init);
  module_exit(nft_limit_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  MODULE_ALIAS_NFT_EXPR("limit");
  MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_LIMIT);
  