netfilter: ipt_CLUSTERIP: only add arp mangle hook when required

Do not register the arp mangling hooks from pernet init path.

As-is, load of the module is enough for these hooks to become active
in each net namespace.

Use checkentry instead so hook is only added if a CLUSTERIP rule is used.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 8f7ca67..6d7ff14 100644 (file)
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -71,6 +71,16 @@ struct clusterip_net {
        /* mutex protects the config->pde*/
        struct mutex mutex;
 #endif
+       unsigned int hook_users;
+};
+
+static unsigned int clusterip_arp_mangle(void *priv, struct sk_buff *skb, const struct nf_hook_state *state);
+
+static const struct nf_hook_ops cip_arp_ops = {
+       .hook = clusterip_arp_mangle,
+       .pf = NFPROTO_ARP,
+       .hooknum = NF_ARP_OUT,
+       .priority = -1
 };
 
 static unsigned int clusterip_net_id __read_mostly;
@@ -458,6 +468,7 @@ clusterip_tg(struct sk_buff *skb, const struct xt_action_param *par)
 static int clusterip_tg_check(const struct xt_tgchk_param *par)
 {
        struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
+       struct clusterip_net *cn = clusterip_pernet(par->net);
        const struct ipt_entry *e = par->entryinfo;
        struct clusterip_config *config;
        int ret, i;
@@ -467,6 +478,9 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
                return -EOPNOTSUPP;
        }
 
+       if (cn->hook_users == UINT_MAX)
+               return -EOVERFLOW;
+
        if (cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP &&
            cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT &&
            cipinfo->hash_mode != CLUSTERIP_HASHMODE_SIP_SPT_DPT) {
@@ -517,6 +531,19 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
                return ret;
        }
 
+       if (cn->hook_users == 0) {
+               ret = nf_register_net_hook(par->net, &cip_arp_ops);
+
+               if (ret < 0) {
+                       clusterip_config_entry_put(config);
+                       clusterip_config_put(config);
+                       nf_ct_netns_put(par->net, par->family);
+                       return ret;
+               }
+       }
+
+       cn->hook_users++;
+
        if (!par->net->xt.clusterip_deprecated_warning) {
                pr_info("ipt_CLUSTERIP is deprecated and it will removed soon, "
                        "use xt_cluster instead\n");
@@ -531,6 +558,7 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
 static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
 {
        const struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
+       struct clusterip_net *cn = clusterip_pernet(par->net);
 
        /* if no more entries are referencing the config, remove it
         * from the list and destroy the proc entry */
@@ -539,6 +567,10 @@ static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
        clusterip_config_put(cipinfo->config);
 
        nf_ct_netns_put(par->net, par->family);
+       cn->hook_users--;
+
+       if (cn->hook_users == 0)
+               nf_unregister_net_hook(par->net, &cip_arp_ops);
 }
 
 #ifdef CONFIG_NETFILTER_XTABLES_COMPAT
@@ -602,9 +634,8 @@ static void arp_print(struct arp_payload *payload)
 #endif
 
 static unsigned int
-arp_mangle(void *priv,
-          struct sk_buff *skb,
-          const struct nf_hook_state *state)
+clusterip_arp_mangle(void *priv, struct sk_buff *skb,
+                    const struct nf_hook_state *state)
 {
        struct arphdr *arp = arp_hdr(skb);
        struct arp_payload *payload;
@@ -654,13 +685,6 @@ arp_mangle(void *priv,
        return NF_ACCEPT;
 }
 
-static const struct nf_hook_ops cip_arp_ops = {
-       .hook = arp_mangle,
-       .pf = NFPROTO_ARP,
-       .hooknum = NF_ARP_OUT,
-       .priority = -1
-};
-
 /***********************************************************************
  * PROC DIR HANDLING
  ***********************************************************************/
@@ -817,20 +841,14 @@ static const struct proc_ops clusterip_proc_ops = {
 static int clusterip_net_init(struct net *net)
 {
        struct clusterip_net *cn = clusterip_pernet(net);
-       int ret;
 
        INIT_LIST_HEAD(&cn->configs);
 
        spin_lock_init(&cn->lock);
 
-       ret = nf_register_net_hook(net, &cip_arp_ops);
-       if (ret < 0)
-               return ret;
-
 #ifdef CONFIG_PROC_FS
        cn->procdir = proc_mkdir("ipt_CLUSTERIP", net->proc_net);
        if (!cn->procdir) {
-               nf_unregister_net_hook(net, &cip_arp_ops);
                pr_err("Unable to proc dir entry\n");
                return -ENOMEM;
        }
@@ -850,7 +868,6 @@ static void clusterip_net_exit(struct net *net)
        cn->procdir = NULL;
        mutex_unlock(&cn->mutex);
 #endif
-       nf_unregister_net_hook(net, &cip_arp_ops);
 }
 
 static struct pernet_operations clusterip_net_ops = {