netfilter: nfnetlink_acct: Adding quota support to accounting framework

nfacct objects already support accounting at the byte and packet
level. As such it is a natural extension to add the possiblity to
define a ceiling limit for both metrics.

All the support for quotas itself is added to nfnetlink acctounting
framework to stay coherent with current accounting object management.
Quota limit checks are implemented in xt_nfacct filter where
statistic collection is already done.

Pablo Neira Ayuso has also contributed to this feature.

Signed-off-by: Mathieu Poirier <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter/nfnetlink_acct.h

···
 
 #include <uapi/linux/netfilter/nfnetlink_acct.h>
 
+enum {
+	NFACCT_NO_QUOTA		= -1,
+	NFACCT_UNDERQUOTA,
+	NFACCT_OVERQUOTA,
+};
 
 struct nf_acct;
 
 struct nf_acct *nfnl_acct_find_get(const char *filter_name);
 void nfnl_acct_put(struct nf_acct *acct);
 void nfnl_acct_update(const struct sk_buff *skb, struct nf_acct *nfacct);
-
+extern int nfnl_acct_overquota(const struct sk_buff *skb,
+			      struct nf_acct *nfacct);
 #endif /* _NFNL_ACCT_H */

include/uapi/linux/netfilter/nfnetlink.h

···
 #define NFNLGRP_CONNTRACK_EXP_DESTROY	NFNLGRP_CONNTRACK_EXP_DESTROY
 	NFNLGRP_NFTABLES,
 #define NFNLGRP_NFTABLES                NFNLGRP_NFTABLES
+	NFNLGRP_ACCT_QUOTA,
+#define NFNLGRP_ACCT_QUOTA		NFNLGRP_ACCT_QUOTA
 	__NFNLGRP_MAX,
 };
 #define NFNLGRP_MAX	(__NFNLGRP_MAX - 1)

include/uapi/linux/netfilter/nfnetlink_acct.h

···
 	NFNL_MSG_ACCT_GET,
 	NFNL_MSG_ACCT_GET_CTRZERO,
 	NFNL_MSG_ACCT_DEL,
+	NFNL_MSG_ACCT_OVERQUOTA,
 	NFNL_MSG_ACCT_MAX
+};
+
+enum nfnl_acct_flags {
+	NFACCT_F_QUOTA_PKTS	= (1 << 0),
+	NFACCT_F_QUOTA_BYTES	= (1 << 1),
+	NFACCT_F_OVERQUOTA	= (1 << 2), /* can't be set from userspace */
 };
 
 enum nfnl_acct_type {
···
 	NFACCT_PKTS,
 	NFACCT_BYTES,
 	NFACCT_USE,
+	NFACCT_FLAGS,
+	NFACCT_QUOTA,
 	__NFACCT_MAX
 };
 #define NFACCT_MAX (__NFACCT_MAX - 1)

net/netfilter/nfnetlink_acct.c

···
 struct nf_acct {
 	atomic64_t		pkts;
 	atomic64_t		bytes;
+	unsigned long		flags;
 	struct list_head	head;
 	atomic_t		refcnt;
 	char			name[NFACCT_NAME_MAX];
 	struct rcu_head		rcu_head;
+	char			data[0];
 };
+
+#define NFACCT_F_QUOTA (NFACCT_F_QUOTA_PKTS | NFACCT_F_QUOTA_BYTES)
 
 static int
 nfnl_acct_new(struct sock *nfnl, struct sk_buff *skb,
···
 {
 	struct nf_acct *nfacct, *matching = NULL;
 	char *acct_name;
+	unsigned int size = 0;
+	u32 flags = 0;
 
 	if (!tb[NFACCT_NAME])
 		return -EINVAL;
···
 			/* reset counters if you request a replacement. */
 			atomic64_set(&matching->pkts, 0);
 			atomic64_set(&matching->bytes, 0);
+			smp_mb__before_clear_bit();
+			/* reset overquota flag if quota is enabled. */
+			if ((matching->flags & NFACCT_F_QUOTA))
+				clear_bit(NFACCT_F_OVERQUOTA, &matching->flags);
 			return 0;
 		}
 		return -EBUSY;
 	}
 
 	nfacct = kzalloc(sizeof(struct nf_acct), GFP_KERNEL);
+	if (tb[NFACCT_FLAGS]) {
+		flags = ntohl(nla_get_be32(tb[NFACCT_FLAGS]));
+		if (flags & ~NFACCT_F_QUOTA)
+			return -EOPNOTSUPP;
+		if ((flags & NFACCT_F_QUOTA) == NFACCT_F_QUOTA)
+			return -EINVAL;
+		if (flags & NFACCT_F_OVERQUOTA)
+			return -EINVAL;
+
+		size += sizeof(u64);
+	}
+
+	nfacct = kzalloc(sizeof(struct nf_acct) + size, GFP_KERNEL);
 	if (nfacct == NULL)
 		return -ENOMEM;
+
+	if (flags & NFACCT_F_QUOTA) {
+		u64 *quota = (u64 *)nfacct->data;
+
+		*quota = be64_to_cpu(nla_get_be64(tb[NFACCT_QUOTA]));
+		nfacct->flags = flags;
+	}
 
 	strncpy(nfacct->name, nla_data(tb[NFACCT_NAME]), NFACCT_NAME_MAX);
 
···
 	if (type == NFNL_MSG_ACCT_GET_CTRZERO) {
 		pkts = atomic64_xchg(&acct->pkts, 0);
 		bytes = atomic64_xchg(&acct->bytes, 0);
+		smp_mb__before_clear_bit();
+		if (acct->flags & NFACCT_F_QUOTA)
+			clear_bit(NFACCT_F_OVERQUOTA, &acct->flags);
 	} else {
 		pkts = atomic64_read(&acct->pkts);
 		bytes = atomic64_read(&acct->bytes);
···
 	    nla_put_be64(skb, NFACCT_BYTES, cpu_to_be64(bytes)) ||
 	    nla_put_be32(skb, NFACCT_USE, htonl(atomic_read(&acct->refcnt))))
 		goto nla_put_failure;
+	if (acct->flags & NFACCT_F_QUOTA) {
+		u64 *quota = (u64 *)acct->data;
 
+		if (nla_put_be32(skb, NFACCT_FLAGS, htonl(acct->flags)) ||
+		    nla_put_be64(skb, NFACCT_QUOTA, cpu_to_be64(*quota)))
+			goto nla_put_failure;
+	}
 	nlmsg_end(skb, nlh);
 	return skb->len;
 
···
 	[NFACCT_NAME] = { .type = NLA_NUL_STRING, .len = NFACCT_NAME_MAX-1 },
 	[NFACCT_BYTES] = { .type = NLA_U64 },
 	[NFACCT_PKTS] = { .type = NLA_U64 },
+	[NFACCT_FLAGS] = { .type = NLA_U32 },
+	[NFACCT_QUOTA] = { .type = NLA_U64 },
 };
 
 static const struct nfnl_callback nfnl_acct_cb[NFNL_MSG_ACCT_MAX] = {
···
 	atomic64_add(skb->len, &nfacct->bytes);
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_update);
+
+static void nfnl_overquota_report(struct nf_acct *nfacct)
+{
+	int ret;
+	struct sk_buff *skb;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+	if (skb == NULL)
+		return;
+
+	ret = nfnl_acct_fill_info(skb, 0, 0, NFNL_MSG_ACCT_OVERQUOTA, 0,
+				  nfacct);
+	if (ret <= 0) {
+		kfree_skb(skb);
+		return;
+	}
+	netlink_broadcast(init_net.nfnl, skb, 0, NFNLGRP_ACCT_QUOTA,
+			  GFP_ATOMIC);
+}
+
+int nfnl_acct_overquota(const struct sk_buff *skb, struct nf_acct *nfacct)
+{
+	u64 now;
+	u64 *quota;
+	int ret = NFACCT_UNDERQUOTA;
+
+	/* no place here if we don't have a quota */
+	if (!(nfacct->flags & NFACCT_F_QUOTA))
+		return NFACCT_NO_QUOTA;
+
+	quota = (u64 *)nfacct->data;
+	now = (nfacct->flags & NFACCT_F_QUOTA_PKTS) ?
+	       atomic64_read(&nfacct->pkts) : atomic64_read(&nfacct->bytes);
+
+	ret = now > *quota;
+
+	if (now >= *quota &&
+	    !test_and_set_bit(NFACCT_F_OVERQUOTA, &nfacct->flags)) {
+		nfnl_overquota_report(nfacct);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfnl_acct_overquota);
 
 static int __init nfnl_acct_init(void)
 {

net/netfilter/xt_nfacct.c

···
 
 static bool nfacct_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
+	int overquota;
 	const struct xt_nfacct_match_info *info = par->targinfo;
 
 	nfnl_acct_update(skb, info->nfacct);
 
-	return true;
+	overquota = nfnl_acct_overquota(skb, info->nfacct);
+
+	return overquota == NFACCT_UNDERQUOTA ? false : true;
 }
 
 static int