Subject: Re: [PATCH 1/1] netfilter: xt_recent: Add optional mask option for xt_recent

From: Pablo Neira Ayuso <[email-masked]>
Date: Wed, 2 May 2012 03:01:19 +0200

On Tue, Mar 06, 2012 at 01:24:44PM +0200, Denys Fedoryshchenko wrote:
> Use case for this feature:
> 1)In some occasions if you need to allow,block,match specific subnet.
> 2)I can use recent as a trigger when netfilter rule matches, with mask 0.0.0.0
> 
> Example:
> 
> If you ping 8.8.8.8, after that you can't ping 2.2.2.10
> 
> Tested for backward compatibility:
> )old (userspace) iptables, new kernel
> )old kernel, new iptables
> )new kernel, new iptables
> 
> Signed-off-by: Denys Fedoryshchenko <[email-masked]>
> ---
>  include/linux/netfilter.h           |   11 +++++
>  include/linux/netfilter/xt_recent.h |   10 +++++
>  net/netfilter/xt_recent.c           |   70 +++++++++++++++++++++++++++++++----
>  3 files changed, 83 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
> index b809265..c132de6 100644
> --- a/include/linux/netfilter.h
> +++ b/include/linux/netfilter.h
> @@ -85,6 +85,17 @@ static inline int NF_DROP_GETERR(int verdict)
> 	return -(verdict >> NF_VERDICT_QBITS);
>  }
> 
> +
> +static inline void nf_inet_addr_mask(const union nf_inet_addr *a1,
> +				    union nf_inet_addr *result,
> +				    const union nf_inet_addr *mask)
> +{
> +	result->all[0] = a1->all[0] & mask->all[0];
> +	result->all[1] = a1->all[1] & mask->all[1];
> +	result->all[2] = a1->all[2] & mask->all[2];
> +	result->all[3] = a1->all[3] & mask->all[3];
> +}

Please, put this function in the xt_recent. I prefer leave it there
until more clients of it show up.

> +
>  static inline int nf_inet_addr_cmp(const union nf_inet_addr *a1,
> 				   const union nf_inet_addr *a2)
>  {
> diff --git a/include/linux/netfilter/xt_recent.h b/include/linux/netfilter/xt_recent.h
> index 83318e0..6ef36c1 100644
> --- a/include/linux/netfilter/xt_recent.h
> +++ b/include/linux/netfilter/xt_recent.h
> @@ -32,4 +32,14 @@ struct xt_recent_mtinfo {
> 	__u8 side;
>  };
> 
> +struct xt_recent_mtinfo_v1 {
> +	__u32 seconds;
> +	__u32 hit_count;
> +	__u8 check_set;
> +	__u8 invert;
> +	char name[XT_RECENT_NAME_LEN];
> +	__u8 side;
> +	union nf_inet_addr mask;
> +};
> +
>  #endif /* _LINUX_NETFILTER_XT_RECENT_H */
> diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
> index d2ff15a..bdc38fa 100644
> --- a/net/netfilter/xt_recent.c
> +++ b/net/netfilter/xt_recent.c
> @@ -75,6 +75,7 @@ struct recent_entry {
>  struct recent_table {
> 	struct list_head	list;
> 	char			name[XT_RECENT_NAME_LEN];
> +	union nf_inet_addr	mask;
> 	unsigned int		refcnt;
> 	unsigned int		entries;
> 	struct list_head	lru_list;
> @@ -228,10 +229,11 @@ recent_mt(const struct sk_buff *skb, struct xt_action_param *par)
>  {
> 	struct net *net = dev_net(par->in ? par->in : par->out);
> 	struct recent_net *recent_net = recent_pernet(net);
> -	const struct xt_recent_mtinfo *info = par->matchinfo;
> +	const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
> 	struct recent_table *t;
> 	struct recent_entry *e;
> 	union nf_inet_addr addr = {};
> +	union nf_inet_addr addr_masked;
> 	u_int8_t ttl;
> 	bool ret = info->invert;
> 
> @@ -261,12 +263,15 @@ recent_mt(const struct sk_buff *skb, struct xt_action_param *par)
> 
> 	spin_lock_bh(&recent_lock);
> 	t = recent_table_lookup(recent_net, info->name);
> -	e = recent_entry_lookup(t, &addr, par->family,
> +
> +	nf_inet_addr_mask(&addr, &addr_masked, &t->mask);
> +
> +	e = recent_entry_lookup(t, &addr_masked, par->family,
> 				(info->check_set & XT_RECENT_TTL) ? ttl : 0);
> 	if (e == NULL) {
> 		if (!(info->check_set & XT_RECENT_SET))
> 			goto out;
> -		e = recent_entry_init(t, &addr, par->family, ttl);
> +		e = recent_entry_init(t, &addr_masked, par->family, ttl);
> 		if (e == NULL)
> 			par->hotdrop = true;
> 		ret = !ret;
> @@ -306,10 +311,10 @@ out:
> 	return ret;
>  }
> 
> -static int recent_mt_check(const struct xt_mtchk_param *par)
> +static int recent_mt_check(const struct xt_mtchk_param *par,
> +	const struct xt_recent_mtinfo_v1 *info)
>  {
> 	struct recent_net *recent_net = recent_pernet(par->net);
> -	const struct xt_recent_mtinfo *info = par->matchinfo;
> 	struct recent_table *t;
>  #ifdef CONFIG_PROC_FS
> 	struct proc_dir_entry *pde;
> @@ -361,6 +366,8 @@ static int recent_mt_check(const struct xt_mtchk_param *par)
> 		goto out;
> 	}
> 	t->refcnt = 1;
> +
> +	memcpy(&t->mask, &info->mask, sizeof(t->mask));
> 	strcpy(t->name, info->name);
> 	INIT_LIST_HEAD(&t->lru_list);
> 	for (i = 0; i < ip_list_hash_size; i++)
> @@ -385,10 +392,37 @@ out:
> 	return ret;
>  }
> 
> +static int recent_mt_check_v0(const struct xt_mtchk_param *par)
> +{
> +	const struct xt_recent_mtinfo_v0 *info_v0 = par->matchinfo;
> +	struct xt_recent_mtinfo_v1 *info_v1 = par->matchinfo;
> +	int ret;
> +
> +	info_v1 = kzalloc(sizeof(struct xt_recent_mtinfo_v1),
> +		    GFP_KERNEL);

Better allocate this in the stack. It's fairly small and it is used
temporarily.

> +	if (info_v1 == NULL)
> +		return -ENOMEM;
> +
> +
> +	/* Copy old data */
> +	memcpy(info_v1, info_v0, sizeof(struct xt_recent_mtinfo));
> +	/* Default mask will make same behavior as old recent */
> +	memset(info_v1->mask.all, 0xFF, sizeof(info_v1->mask.all));
> +	ret = recent_mt_check(par, info_v1);
> +
> +	kfree(info_v1);
> +	return ret;
> +}
> +
> +static int recent_mt_check_v1(const struct xt_mtchk_param *par)
> +{
> +	return recent_mt_check(par, par->matchinfo);
> +}
> +
>  static void recent_mt_destroy(const struct xt_mtdtor_param *par)
>  {
> 	struct recent_net *recent_net = recent_pernet(par->net);
> -	const struct xt_recent_mtinfo *info = par->matchinfo;
> +	const struct xt_recent_mtinfo_v1 *info = par->matchinfo;
> 	struct recent_table *t;
> 
> 	mutex_lock(&recent_mutex);
> @@ -625,7 +659,7 @@ static struct xt_match recent_mt_reg[] __read_mostly = {
> 		.family     = NFPROTO_IPV4,
> 		.match      = recent_mt,
> 		.matchsize  = sizeof(struct xt_recent_mtinfo),
> -		.checkentry = recent_mt_check,
> +		.checkentry = recent_mt_check_v0,
> 		.destroy    = recent_mt_destroy,
> 		.me         = THIS_MODULE,
> 	},
> @@ -635,10 +669,30 @@ static struct xt_match recent_mt_reg[] __read_mostly = {
> 		.family     = NFPROTO_IPV6,
> 		.match      = recent_mt,
> 		.matchsize  = sizeof(struct xt_recent_mtinfo),
> -		.checkentry = recent_mt_check,
> +		.checkentry = recent_mt_check_v0,
> 		.destroy    = recent_mt_destroy,
> 		.me         = THIS_MODULE,
> 	},
> +	{
> +		.name       = "recent",
> +		.revision   = 1,
> +		.family     = NFPROTO_IPV4,
> +		.match      = recent_mt,
> +		.matchsize  = sizeof(struct xt_recent_mtinfo_v1),
> +		.checkentry = recent_mt_check_v1,
> +		.destroy    = recent_mt_destroy,
> +		.me         = THIS_MODULE,
> +	},
> +	{
> +		.name       = "recent",
> +		.revision   = 1,
> +		.family     = NFPROTO_IPV6,
> +		.match      = recent_mt,
> +		.matchsize  = sizeof(struct xt_recent_mtinfo_v1),
> +		.checkentry = recent_mt_check_v1,
> +		.destroy    = recent_mt_destroy,
> +		.me         = THIS_MODULE,
> +	}
>  };
> 
>  static int __init recent_mt_init(void)
> --
> 1.7.3.4