netfilter: reduce size of hook entry point locations

struct net contains:

struct nf_hook_entries __rcu *hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];

which store the hook entry point locations for the various protocol
families and the hooks.

Using array results in compact c code when doing accesses, i.e.
  x = rcu_dereference(net->nf.hooks[pf][hook]);

but its also wasting a lot of memory, as most families are
not used.

So split the array into those families that are used, which
are only 5 (instead of 13).  In most cases, the 'pf' argument is
constant, i.e. gcc removes switch statement.

struct net before:
 /* size: 5184, cachelines: 81, members: 46 */
after:
 /* size: 4672, cachelines: 73, members: 46 */

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

3 files changed, 50 insertions, 11 deletions

diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index c2eea1b..27f1d4f 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -991,7 +991,7 @@ int br_nf_hook_thresh(unsigned int hook, struct net *net,
 	unsigned int i;
 	int ret;
 
-	e = rcu_dereference(net->nf.hooks[NFPROTO_BRIDGE][hook]);
+	e = rcu_dereference(net->nf.hooks_bridge[hook]);
 	if (!e)
 		return okfn(net, sk, skb);
 
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 6921f9f..a6eaaf3 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -264,8 +264,23 @@ out_assign:
 
 static struct nf_hook_entries __rcu **nf_hook_entry_head(struct net *net, const struct nf_hook_ops *reg)
 {
-	if (reg->pf != NFPROTO_NETDEV)
-		return net->nf.hooks[reg->pf]+reg->hooknum;
+	switch (reg->pf) {
+	case NFPROTO_NETDEV:
+		break;
+	case NFPROTO_ARP:
+		return net->nf.hooks_arp + reg->hooknum;
+	case NFPROTO_BRIDGE:
+		return net->nf.hooks_bridge + reg->hooknum;
+	case NFPROTO_IPV4:
+		return net->nf.hooks_ipv4 + reg->hooknum;
+	case NFPROTO_IPV6:
+		return net->nf.hooks_ipv6 + reg->hooknum;
+	case NFPROTO_DECNET:
+		return net->nf.hooks_decnet + reg->hooknum;
+	default:
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
 
 #ifdef CONFIG_NETFILTER_INGRESS
 	if (reg->hooknum == NF_NETDEV_INGRESS) {
@@ -534,14 +549,21 @@ void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
 EXPORT_SYMBOL(nf_nat_decode_session_hook);
 #endif
 
-static int __net_init netfilter_net_init(struct net *net)
+static void __net_init __netfilter_net_init(struct nf_hook_entries *e[NF_MAX_HOOKS])
 {
-	int i, h;
+	int h;
 
-	for (i = 0; i < ARRAY_SIZE(net->nf.hooks); i++) {
-		for (h = 0; h < NF_MAX_HOOKS; h++)
-			RCU_INIT_POINTER(net->nf.hooks[i][h], NULL);
-	}
+	for (h = 0; h < NF_MAX_HOOKS; h++)
+		RCU_INIT_POINTER(e[h], NULL);
+}
+
+static int __net_init netfilter_net_init(struct net *net)
+{
+	__netfilter_net_init(net->nf.hooks_ipv4);
+	__netfilter_net_init(net->nf.hooks_ipv6);
+	__netfilter_net_init(net->nf.hooks_arp);
+	__netfilter_net_init(net->nf.hooks_bridge);
+	__netfilter_net_init(net->nf.hooks_decnet);
 
 #ifdef CONFIG_PROC_FS
 	net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
diff --git a/net/netfilter/nf_queue.c b/net/netfilter/nf_queue.c
index 4e42a4a..836aeb0 100644
--- a/net/netfilter/nf_queue.c
+++ b/net/netfilter/nf_queue.c
@@ -201,6 +201,23 @@ repeat:
 	return NF_ACCEPT;
 }
 
+static struct nf_hook_entries *nf_hook_entries_head(const struct net *net, u8 pf, u8 hooknum)
+{
+	switch (pf) {
+	case NFPROTO_BRIDGE:
+		return rcu_dereference(net->nf.hooks_bridge[hooknum]);
+	case NFPROTO_IPV4:
+		return rcu_dereference(net->nf.hooks_ipv4[hooknum]);
+	case NFPROTO_IPV6:
+		return rcu_dereference(net->nf.hooks_ipv6[hooknum]);
+	default:
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
+
+	return NULL;
+}
+
 /* Caller must hold rcu read-side lock */
 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 {
@@ -216,12 +233,12 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 	net = entry->state.net;
 	pf = entry->state.pf;
 
-	hooks = rcu_dereference(net->nf.hooks[pf][entry->state.hook]);
+	hooks = nf_hook_entries_head(net, pf, entry->state.hook);
 
 	nf_queue_entry_release_refs(entry);
 
 	i = entry->hook_index;
-	if (WARN_ON_ONCE(i >= hooks->num_hook_entries)) {
+	if (WARN_ON_ONCE(!hooks || i >= hooks->num_hook_entries)) {
 		kfree_skb(skb);
 		kfree(entry);
 		return;