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netfilter: xt_quota: fix the behavior of xt_quota module

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A major flaw of the current xt_quota module is that quota in a specific
rule gets reset every time there is a rule change in the same table. It
makes the xt_quota module not very useful in a table in which iptables
rules are changed at run time. This fix introduces a new counter that is
visible to userspace as the remaining quota of the current rule. When
userspace restores the rules in a table, it can restore the counter to
the remaining quota instead of resetting it to the full quota.

Signed-off-by: Chenbo Feng <fengc@google.com>
Suggested-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Chenbo Feng 2018-10-01 18:23:08 -07:00 committed by Pablo Neira Ayuso
parent a2d88182d2
commit e9837e55b0
2 changed files with 26 additions and 35 deletions
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8
include/uapi/linux/netfilter/xt_quota.h
View File

@ -15,9 +15,11 @@ struct xt_quota_info {
__u32 flags;
__u32 pad;
__aligned_u64 quota;
/* Used internally by the kernel */
struct xt_quota_priv *master;
#ifdef __KERNEL__
atomic64_t counter;
#else
__aligned_u64 remain;
#endif
};
#endif /* _XT_QUOTA_H */

51
net/netfilter/xt_quota.c
View File

@ -11,11 +11,6 @@
#include <linux/netfilter/xt_quota.h>
#include <linux/module.h>
struct xt_quota_priv {
spinlock_t lock;
uint64_t quota;
};
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
MODULE_DESCRIPTION("Xtables: countdown quota match");
@ -26,54 +21,48 @@ static bool
quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
struct xt_quota_info *q = (void *)par->matchinfo;
struct xt_quota_priv *priv = q->master;
u64 current_count = atomic64_read(&q->counter);
bool ret = q->flags & XT_QUOTA_INVERT;
u64 old_count, new_count;
spin_lock_bh(&priv->lock);
if (priv->quota >= skb->len) {
priv->quota -= skb->len;
ret = !ret;
} else {
/* we do not allow even small packets from now on */
priv->quota = 0;
}
spin_unlock_bh(&priv->lock);
do {
if (current_count == 1)
return ret;
if (current_count <= skb->len) {
atomic64_set(&q->counter, 1);
return ret;
}
old_count = current_count;
new_count = current_count - skb->len;
current_count = atomic64_cmpxchg(&q->counter, old_count,
new_count);
} while (current_count != old_count);
return !ret;
}
static int quota_mt_check(const struct xt_mtchk_param *par)
{
struct xt_quota_info *q = par->matchinfo;
BUILD_BUG_ON(sizeof(atomic64_t) != sizeof(__aligned_u64));
if (q->flags & ~XT_QUOTA_MASK)
return -EINVAL;
if (atomic64_read(&q->counter) > q->quota + 1)
return -ERANGE;
q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
if (q->master == NULL)
return -ENOMEM;
spin_lock_init(&q->master->lock);
q->master->quota = q->quota;
if (atomic64_read(&q->counter) == 0)
atomic64_set(&q->counter, q->quota + 1);
return 0;
}
static void quota_mt_destroy(const struct xt_mtdtor_param *par)
{
const struct xt_quota_info *q = par->matchinfo;
kfree(q->master);
}
static struct xt_match quota_mt_reg __read_mostly = {
.name = "quota",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = quota_mt,
.checkentry = quota_mt_check,
.destroy = quota_mt_destroy,
.matchsize = sizeof(struct xt_quota_info),
.usersize = offsetof(struct xt_quota_info, master),
.me = THIS_MODULE,
};