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Commit e3b37f11 authored by Aaron Conole's avatar Aaron Conole Committed by Pablo Neira Ayuso
Browse files

netfilter: replace list_head with single linked list 



The netfilter hook list never uses the prev pointer, and so can be trimmed to
be a simple singly-linked list.

In addition to having a more light weight structure for hook traversal,
struct net becomes 5568 bytes (down from 6400) and struct net_device becomes
2176 bytes (down from 2240).

Signed-off-by: default avatarAaron Conole <aconole@bytheb.org>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 54f17bbc

include/linux/netdevice.h

+1 −1
Original line number Diff line number Diff line
@@ -1783,7 +1783,7 @@ struct net_device { 
#endif

	struct netdev_queue __rcu *ingress_queue;

#ifdef CONFIG_NETFILTER_INGRESS

	struct list_head	nf_hooks_ingress;

	struct nf_hook_entry __rcu *nf_hooks_ingress;

#endif



	unsigned char		broadcast[MAX_ADDR_LEN];

include/linux/netfilter.h

+34 −29
Original line number Diff line number Diff line
@@ -55,12 +55,34 @@ struct nf_hook_state { 
	struct net_device *out;

	struct sock *sk;

	struct net *net;

	struct list_head *hook_list;

	struct nf_hook_entry __rcu *hook_entries;

	int (*okfn)(struct net *, struct sock *, struct sk_buff *);

};



typedef unsigned int nf_hookfn(void *priv,

			       struct sk_buff *skb,

			       const struct nf_hook_state *state);

struct nf_hook_ops {

	struct list_head	list;



	/* User fills in from here down. */

	nf_hookfn		*hook;

	struct net_device	*dev;

	void			*priv;

	u_int8_t		pf;

	unsigned int		hooknum;

	/* Hooks are ordered in ascending priority. */

	int			priority;

};



struct nf_hook_entry {

	struct nf_hook_entry __rcu	*next;

	struct nf_hook_ops		ops;

	const struct nf_hook_ops	*orig_ops;

};



static inline void nf_hook_state_init(struct nf_hook_state *p,

				      struct list_head *hook_list,

				      struct nf_hook_entry *hook_entry,

				      unsigned int hook,

				      int thresh, u_int8_t pf,

				      struct net_device *indev,
@@ -76,26 +98,11 @@ static inline void nf_hook_state_init(struct nf_hook_state *p, 
	p->out = outdev;

	p->sk = sk;

	p->net = net;

	p->hook_list = hook_list;

	RCU_INIT_POINTER(p->hook_entries, hook_entry);

	p->okfn = okfn;

}



typedef unsigned int nf_hookfn(void *priv,

			       struct sk_buff *skb,

			       const struct nf_hook_state *state);



struct nf_hook_ops {

	struct list_head 	list;



	/* User fills in from here down. */

	nf_hookfn		*hook;

	struct net_device	*dev;

	void			*priv;

	u_int8_t		pf;

	unsigned int		hooknum;

	/* Hooks are ordered in ascending priority. */

	int			priority;

};



struct nf_sockopt_ops {

	struct list_head list;
@@ -161,7 +168,8 @@ static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook, 
				 int (*okfn)(struct net *, struct sock *, struct sk_buff *),

				 int thresh)

{

	struct list_head *hook_list;

	struct nf_hook_entry *hook_head;

	int ret = 1;



#ifdef HAVE_JUMP_LABEL

	if (__builtin_constant_p(pf) &&
@@ -170,23 +178,20 @@ static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook, 
		return 1;

#endif



	hook_list = &net->nf.hooks[pf][hook];



	if (!list_empty(hook_list)) {

	rcu_read_lock();

	hook_head = rcu_dereference(net->nf.hooks[pf][hook]);

	if (hook_head) {

		struct nf_hook_state state;

		int ret;



		/* We may already have this, but read-locks nest anyway */

		rcu_read_lock();

		nf_hook_state_init(&state, hook_list, hook, thresh,

		nf_hook_state_init(&state, hook_head, hook, thresh,

				   pf, indev, outdev, sk, net, okfn);



		ret = nf_hook_slow(skb, &state);

	}

	rcu_read_unlock();



	return ret;

}

	return 1;

}



static inline int nf_hook(u_int8_t pf, unsigned int hook, struct net *net,

			  struct sock *sk, struct sk_buff *skb,

include/linux/netfilter_ingress.h

+12 −5
Original line number Diff line number Diff line
@@ -11,23 +11,30 @@ static inline bool nf_hook_ingress_active(const struct sk_buff *skb) 
	if (!static_key_false(&nf_hooks_needed[NFPROTO_NETDEV][NF_NETDEV_INGRESS]))

		return false;

#endif

	return !list_empty(&skb->dev->nf_hooks_ingress);

	return rcu_access_pointer(skb->dev->nf_hooks_ingress);

}



/* caller must hold rcu_read_lock */

static inline int nf_hook_ingress(struct sk_buff *skb)

{

	struct nf_hook_entry *e = rcu_dereference(skb->dev->nf_hooks_ingress);

	struct nf_hook_state state;



	nf_hook_state_init(&state, &skb->dev->nf_hooks_ingress,

			   NF_NETDEV_INGRESS, INT_MIN, NFPROTO_NETDEV,

			   skb->dev, NULL, NULL, dev_net(skb->dev), NULL);

	/* Must recheck the ingress hook head, in the event it became NULL

	 * after the check in nf_hook_ingress_active evaluated to true.

	 */

	if (unlikely(!e))

		return 0;



	nf_hook_state_init(&state, e, NF_NETDEV_INGRESS, INT_MIN,

			   NFPROTO_NETDEV, skb->dev, NULL, NULL,

			   dev_net(skb->dev), NULL);

	return nf_hook_slow(skb, &state);

}



static inline void nf_hook_ingress_init(struct net_device *dev)

{

	INIT_LIST_HEAD(&dev->nf_hooks_ingress);

	RCU_INIT_POINTER(dev->nf_hooks_ingress, NULL);

}

#else /* CONFIG_NETFILTER_INGRESS */

static inline int nf_hook_ingress_active(struct sk_buff *skb)

include/net/netfilter/nf_queue.h

+1 −2
Original line number Diff line number Diff line
@@ -11,7 +11,6 @@ struct nf_queue_entry { 
	struct sk_buff		*skb;

	unsigned int		id;



	struct nf_hook_ops	*elem;

	struct nf_hook_state	state;

	u16			size; /* sizeof(entry) + saved route keys */
@@ -25,7 +24,7 @@ struct nf_queue_handler { 
	int		(*outfn)(struct nf_queue_entry *entry,

				 unsigned int queuenum);

	void		(*nf_hook_drop)(struct net *net,

					struct nf_hook_ops *ops);

					const struct nf_hook_entry *hooks);

};



void nf_register_queue_handler(struct net *net, const struct nf_queue_handler *qh);

include/net/netns/netfilter.h

+1 −1
Original line number Diff line number Diff line
@@ -16,6 +16,6 @@ struct netns_nf { 
#ifdef CONFIG_SYSCTL

	struct ctl_table_header *nf_log_dir_header;

#endif

	struct list_head hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];

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

};

#endif