netfilter.h 11.4 KB
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#ifndef __LINUX_NETFILTER_H
#define __LINUX_NETFILTER_H

#ifdef __KERNEL__
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/if.h>
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#include <linux/in.h>
#include <linux/in6.h>
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#include <linux/wait.h>
#include <linux/list.h>
#endif
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#include <linux/types.h>
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#include <linux/compiler.h>
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#include <linux/sysctl.h>
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/* Responses from hook functions. */
#define NF_DROP 0
#define NF_ACCEPT 1
#define NF_STOLEN 2
#define NF_QUEUE 3
#define NF_REPEAT 4
#define NF_STOP 5
#define NF_MAX_VERDICT NF_STOP

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/* we overload the higher bits for encoding auxiliary data such as the queue
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 * number or errno values. Not nice, but better than additional function
 * arguments. */
#define NF_VERDICT_MASK 0x000000ff

/* extra verdict flags have mask 0x0000ff00 */
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#define NF_VERDICT_FLAG_QUEUE_BYPASS	0x00008000
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/* queue number (NF_QUEUE) or errno (NF_DROP) */
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#define NF_VERDICT_QMASK 0xffff0000
#define NF_VERDICT_QBITS 16

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#define NF_QUEUE_NR(x) ((((x) << 16) & NF_VERDICT_QMASK) | NF_QUEUE)
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#define NF_DROP_ERR(x) (((-x) << 16) | NF_DROP)
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/* only for userspace compatibility */
#ifndef __KERNEL__
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/* Generic cache responses from hook functions.
   <= 0x2000 is used for protocol-flags. */
#define NFC_UNKNOWN 0x4000
#define NFC_ALTERED 0x8000
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/* NF_VERDICT_BITS should be 8 now, but userspace might break if this changes */
#define NF_VERDICT_BITS 16
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#endif
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enum nf_inet_hooks {
	NF_INET_PRE_ROUTING,
	NF_INET_LOCAL_IN,
	NF_INET_FORWARD,
	NF_INET_LOCAL_OUT,
	NF_INET_POST_ROUTING,
	NF_INET_NUMHOOKS
};

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enum {
	NFPROTO_UNSPEC =  0,
	NFPROTO_IPV4   =  2,
	NFPROTO_ARP    =  3,
	NFPROTO_BRIDGE =  7,
	NFPROTO_IPV6   = 10,
	NFPROTO_DECNET = 12,
	NFPROTO_NUMPROTO,
};

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union nf_inet_addr {
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	__u32		all[4];
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	__be32		ip;
	__be32		ip6[4];
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	struct in_addr	in;
	struct in6_addr	in6;
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};

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#ifdef __KERNEL__
#ifdef CONFIG_NETFILTER
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static inline int NF_DROP_GETERR(int verdict)
{
	return -(verdict >> NF_VERDICT_QBITS);
}
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static inline int nf_inet_addr_cmp(const union nf_inet_addr *a1,
				   const union nf_inet_addr *a2)
{
	return a1->all[0] == a2->all[0] &&
	       a1->all[1] == a2->all[1] &&
	       a1->all[2] == a2->all[2] &&
	       a1->all[3] == a2->all[3];
}

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static inline void nf_inet_addr_mask(const union nf_inet_addr *a1,
				     union nf_inet_addr *result,
				     const union nf_inet_addr *mask)
{
	result->all[0] = a1->all[0] & mask->all[0];
	result->all[1] = a1->all[1] & mask->all[1];
	result->all[2] = a1->all[2] & mask->all[2];
	result->all[3] = a1->all[3] & mask->all[3];
}

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extern void netfilter_init(void);

/* Largest hook number + 1 */
#define NF_MAX_HOOKS 8

struct sk_buff;

typedef unsigned int nf_hookfn(unsigned int hooknum,
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			       struct sk_buff *skb,
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			       const struct net_device *in,
			       const struct net_device *out,
			       int (*okfn)(struct sk_buff *));

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struct nf_hook_ops {
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	struct list_head list;

	/* User fills in from here down. */
	nf_hookfn *hook;
	struct module *owner;
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	u_int8_t pf;
	unsigned int hooknum;
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	/* Hooks are ordered in ascending priority. */
	int priority;
};

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struct nf_sockopt_ops {
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	struct list_head list;

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	u_int8_t pf;
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	/* Non-inclusive ranges: use 0/0/NULL to never get called. */
	int set_optmin;
	int set_optmax;
	int (*set)(struct sock *sk, int optval, void __user *user, unsigned int len);
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#ifdef CONFIG_COMPAT
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	int (*compat_set)(struct sock *sk, int optval,
			void __user *user, unsigned int len);
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#endif
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	int get_optmin;
	int get_optmax;
	int (*get)(struct sock *sk, int optval, void __user *user, int *len);
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#ifdef CONFIG_COMPAT
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	int (*compat_get)(struct sock *sk, int optval,
			void __user *user, int *len);
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#endif
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	/* Use the module struct to lock set/get code in place */
	struct module *owner;
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};

/* Function to register/unregister hook points. */
int nf_register_hook(struct nf_hook_ops *reg);
void nf_unregister_hook(struct nf_hook_ops *reg);
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int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n);
void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n);
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/* Functions to register get/setsockopt ranges (non-inclusive).  You
   need to check permissions yourself! */
int nf_register_sockopt(struct nf_sockopt_ops *reg);
void nf_unregister_sockopt(struct nf_sockopt_ops *reg);

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extern struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
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#if defined(CONFIG_JUMP_LABEL)
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#include <linux/static_key.h>
extern struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
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static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
{
	if (__builtin_constant_p(pf) &&
	    __builtin_constant_p(hook))
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		return static_key_false(&nf_hooks_needed[pf][hook]);
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	return !list_empty(&nf_hooks[pf][hook]);
}
#else
static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
{
	return !list_empty(&nf_hooks[pf][hook]);
}
#endif

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int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
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		 struct net_device *indev, struct net_device *outdev,
		 int (*okfn)(struct sk_buff *), int thresh);

/**
 *	nf_hook_thresh - call a netfilter hook
 *	
 *	Returns 1 if the hook has allowed the packet to pass.  The function
 *	okfn must be invoked by the caller in this case.  Any other return
 *	value indicates the packet has been consumed by the hook.
 */
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static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,
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				 struct sk_buff *skb,
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				 struct net_device *indev,
				 struct net_device *outdev,
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				 int (*okfn)(struct sk_buff *), int thresh)
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{
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	if (nf_hooks_active(pf, hook))
		return nf_hook_slow(pf, hook, skb, indev, outdev, okfn, thresh);
	return 1;
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}

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static inline int nf_hook(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
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			  struct net_device *indev, struct net_device *outdev,
			  int (*okfn)(struct sk_buff *))
{
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	return nf_hook_thresh(pf, hook, skb, indev, outdev, okfn, INT_MIN);
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}
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/* Activate hook; either okfn or kfree_skb called, unless a hook
   returns NF_STOLEN (in which case, it's up to the hook to deal with
   the consequences).

   Returns -ERRNO if packet dropped.  Zero means queued, stolen or
   accepted.
*/

/* RR:
   > I don't want nf_hook to return anything because people might forget
   > about async and trust the return value to mean "packet was ok".

   AK:
   Just document it clearly, then you can expect some sense from kernel
   coders :)
*/

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static inline int
NF_HOOK_THRESH(uint8_t pf, unsigned int hook, struct sk_buff *skb,
	       struct net_device *in, struct net_device *out,
	       int (*okfn)(struct sk_buff *), int thresh)
{
	int ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, thresh);
	if (ret == 1)
		ret = okfn(skb);
	return ret;
}
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static inline int
NF_HOOK_COND(uint8_t pf, unsigned int hook, struct sk_buff *skb,
	     struct net_device *in, struct net_device *out,
	     int (*okfn)(struct sk_buff *), bool cond)
{
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	int ret;

	if (!cond ||
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	    ((ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN)) == 1))
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		ret = okfn(skb);
	return ret;
}
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static inline int
NF_HOOK(uint8_t pf, unsigned int hook, struct sk_buff *skb,
	struct net_device *in, struct net_device *out,
	int (*okfn)(struct sk_buff *))
{
	return NF_HOOK_THRESH(pf, hook, skb, in, out, okfn, INT_MIN);
}
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/* Call setsockopt() */
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int nf_setsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,
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		  unsigned int len);
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int nf_getsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,
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		  int *len);
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#ifdef CONFIG_COMPAT
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int compat_nf_setsockopt(struct sock *sk, u_int8_t pf, int optval,
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		char __user *opt, unsigned int len);
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int compat_nf_getsockopt(struct sock *sk, u_int8_t pf, int optval,
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		char __user *opt, int *len);
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#endif
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/* Call this before modifying an existing packet: ensures it is
   modifiable and linear to the point you care about (writable_len).
   Returns true or false. */
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extern int skb_make_writable(struct sk_buff *skb, unsigned int writable_len);
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struct flowi;
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struct nf_queue_entry;
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struct nf_afinfo {
	unsigned short	family;
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	__sum16		(*checksum)(struct sk_buff *skb, unsigned int hook,
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				    unsigned int dataoff, u_int8_t protocol);
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	__sum16		(*checksum_partial)(struct sk_buff *skb,
					    unsigned int hook,
					    unsigned int dataoff,
					    unsigned int len,
					    u_int8_t protocol);
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	int		(*route)(struct net *net, struct dst_entry **dst,
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				 struct flowi *fl, bool strict);
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	void		(*saveroute)(const struct sk_buff *skb,
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				     struct nf_queue_entry *entry);
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	int		(*reroute)(struct sk_buff *skb,
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				   const struct nf_queue_entry *entry);
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	int		route_key_size;
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};

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extern const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO];
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static inline const struct nf_afinfo *nf_get_afinfo(unsigned short family)
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{
	return rcu_dereference(nf_afinfo[family]);
}
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static inline __sum16
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nf_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff,
	    u_int8_t protocol, unsigned short family)
{
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	const struct nf_afinfo *afinfo;
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	__sum16 csum = 0;
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	rcu_read_lock();
	afinfo = nf_get_afinfo(family);
	if (afinfo)
		csum = afinfo->checksum(skb, hook, dataoff, protocol);
	rcu_read_unlock();
	return csum;
}

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static inline __sum16
nf_checksum_partial(struct sk_buff *skb, unsigned int hook,
		    unsigned int dataoff, unsigned int len,
		    u_int8_t protocol, unsigned short family)
{
	const struct nf_afinfo *afinfo;
	__sum16 csum = 0;

	rcu_read_lock();
	afinfo = nf_get_afinfo(family);
	if (afinfo)
		csum = afinfo->checksum_partial(skb, hook, dataoff, len,
						protocol);
	rcu_read_unlock();
	return csum;
}

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extern int nf_register_afinfo(const struct nf_afinfo *afinfo);
extern void nf_unregister_afinfo(const struct nf_afinfo *afinfo);
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#include <net/flow.h>
extern void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);

static inline void
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nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl, u_int8_t family)
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{
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#ifdef CONFIG_NF_NAT_NEEDED
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	void (*decodefn)(struct sk_buff *, struct flowi *);

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	if (family == AF_INET) {
		rcu_read_lock();
		decodefn = rcu_dereference(ip_nat_decode_session);
		if (decodefn)
			decodefn(skb, fl);
		rcu_read_unlock();
	}
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#endif
}

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#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
extern struct proc_dir_entry *proc_net_netfilter;
#endif

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#else /* !CONFIG_NETFILTER */
#define NF_HOOK(pf, hook, skb, indev, outdev, okfn) (okfn)(skb)
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#define NF_HOOK_COND(pf, hook, skb, indev, outdev, okfn, cond) (okfn)(skb)
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static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,
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				 struct sk_buff *skb,
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				 struct net_device *indev,
				 struct net_device *outdev,
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				 int (*okfn)(struct sk_buff *), int thresh)
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{
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	return okfn(skb);
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}
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static inline int nf_hook(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
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			  struct net_device *indev, struct net_device *outdev,
			  int (*okfn)(struct sk_buff *))
{
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	return 1;
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}
struct flowi;
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static inline void
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nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl, u_int8_t family)
{
}
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#endif /*CONFIG_NETFILTER*/

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#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
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extern void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu;
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extern void nf_ct_attach(struct sk_buff *, struct sk_buff *);
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extern void (*nf_ct_destroy)(struct nf_conntrack *) __rcu;
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struct nf_conn;
struct nlattr;

struct nfq_ct_hook {
	size_t (*build_size)(const struct nf_conn *ct);
	int (*build)(struct sk_buff *skb, struct nf_conn *ct);
	int (*parse)(const struct nlattr *attr, struct nf_conn *ct);
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};
extern struct nfq_ct_hook __rcu *nfq_ct_hook;

struct nfq_ct_nat_hook {
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	void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct,
			   u32 ctinfo, int off);
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};
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extern struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook;
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#else
static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
#endif

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#endif /*__KERNEL__*/
#endif /*__LINUX_NETFILTER_H*/