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

From: Pablo Neira Ayuso <[email-masked]>
Date: Wed, 6 Jun 2012 02:01:00 +0200

On Thu, May 17, 2012 at 11:07:18PM +0300, 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
> 
> Tested for backward compatibility:
> )old (userspace) iptables, new kernel
> )old kernel, new iptables
> )new kernel, new iptables
> 
> For v2:
>  As Pablo Neira Ayuso suggested, moved nf_inet_addr_mask to xt_recent.h
>  and made info_v1 as a stack variable.

Applied with some minor glitches (see below).

Thanks Denys.

> Signed-off-by: Denys Fedoryshchenko <[email-masked]>
> CC: Pablo Neira Ayuso <[email-masked]>
> ---
>  include/linux/netfilter/xt_recent.h |   20 +++++++++++
>  net/netfilter/xt_recent.c           |   62 ++++++++++++++++++++++++++++++----
>  2 files changed, 74 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/netfilter/xt_recent.h b/include/linux/netfilter/xt_recent.h
> index 83318e0..5f69ebc 100644
> --- a/include/linux/netfilter/xt_recent.h
> +++ b/include/linux/netfilter/xt_recent.h
> @@ -32,4 +32,24 @@ 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;
> +};
> +
> +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];

Yes, I told you to move this to xt_recent. But then I noticed that
nf_inet_addr_cmp in linux/netfilter.h. and well, this is static inline
and other may get some benefit with it.

Yes, I'm changing my mind :-).

> +}
> +
>  #endif /* _LINUX_NETFILTER_XT_RECENT_H */
> diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
> index fc0d6db..ca4375c 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;

I've put addr_masked with addr (same line).

>  	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 +392,29 @@ 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;
> +	int ret;
> +
> +	/* 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);
> +	return ret;

return recent_mt_check(...)

I removed that ret variable.

> +}
> +
> +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 +651,7 @@ 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 +661,30 @@ 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
> 
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