root/include/linux/netfilter/x_tables.h

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INCLUDED FROM

DEFINITIONS

This source file includes following definitions.
  1. xt_write_recseq_begin
  2. xt_write_recseq_end
  3. ifname_compare_aligned
#ifndef _X_TABLES_H
#define _X_TABLES_H


#include <linux/netdevice.h>
#include <uapi/linux/netfilter/x_tables.h>

/**
 * struct xt_action_param - parameters for matches/targets
 *
 * @match:      the match extension
 * @target:     the target extension
 * @matchinfo:  per-match data
 * @targetinfo: per-target data
 * @in:         input netdevice
 * @out:        output netdevice
 * @fragoff:    packet is a fragment, this is the data offset
 * @thoff:      position of transport header relative to skb->data
 * @hook:       hook number given packet came from
 * @family:     Actual NFPROTO_* through which the function is invoked
 *              (helpful when match->family == NFPROTO_UNSPEC)
 *
 * Fields written to by extensions:
 *
 * @hotdrop:    drop packet if we had inspection problems
 * Network namespace obtainable using dev_net(in/out)
 */
struct xt_action_param {
        union {
                const struct xt_match *match;
                const struct xt_target *target;
        };
        union {
                const void *matchinfo, *targinfo;
        };
        const struct net_device *in, *out;
        int fragoff;
        unsigned int thoff;
        unsigned int hooknum;
        u_int8_t family;
        bool hotdrop;
};

/**
 * struct xt_mtchk_param - parameters for match extensions'
 * checkentry functions
 *
 * @net:        network namespace through which the check was invoked
 * @table:      table the rule is tried to be inserted into
 * @entryinfo:  the family-specific rule data
 *              (struct ipt_ip, ip6t_ip, arpt_arp or (note) ebt_entry)
 * @match:      struct xt_match through which this function was invoked
 * @matchinfo:  per-match data
 * @hook_mask:  via which hooks the new rule is reachable
 * Other fields as above.
 */
struct xt_mtchk_param {
        struct net *net;
        const char *table;
        const void *entryinfo;
        const struct xt_match *match;
        void *matchinfo;
        unsigned int hook_mask;
        u_int8_t family;
};

/**
 * struct xt_mdtor_param - match destructor parameters
 * Fields as above.
 */
struct xt_mtdtor_param {
        struct net *net;
        const struct xt_match *match;
        void *matchinfo;
        u_int8_t family;
};

/**
 * struct xt_tgchk_param - parameters for target extensions'
 * checkentry functions
 *
 * @entryinfo:  the family-specific rule data
 *              (struct ipt_entry, ip6t_entry, arpt_entry, ebt_entry)
 *
 * Other fields see above.
 */
struct xt_tgchk_param {
        struct net *net;
        const char *table;
        const void *entryinfo;
        const struct xt_target *target;
        void *targinfo;
        unsigned int hook_mask;
        u_int8_t family;
};

/* Target destructor parameters */
struct xt_tgdtor_param {
        struct net *net;
        const struct xt_target *target;
        void *targinfo;
        u_int8_t family;
};

struct xt_match {
        struct list_head list;

        const char name[XT_EXTENSION_MAXNAMELEN];
        u_int8_t revision;

        /* Return true or false: return FALSE and set *hotdrop = 1 to
           force immediate packet drop. */
        /* Arguments changed since 2.6.9, as this must now handle
           non-linear skb, using skb_header_pointer and
           skb_ip_make_writable. */
        bool (*match)(const struct sk_buff *skb,
                      struct xt_action_param *);

        /* Called when user tries to insert an entry of this type. */
        int (*checkentry)(const struct xt_mtchk_param *);

        /* Called when entry of this type deleted. */
        void (*destroy)(const struct xt_mtdtor_param *);
#ifdef CONFIG_COMPAT
        /* Called when userspace align differs from kernel space one */
        void (*compat_from_user)(void *dst, const void *src);
        int (*compat_to_user)(void __user *dst, const void *src);
#endif
        /* Set this to THIS_MODULE if you are a module, otherwise NULL */
        struct module *me;

        const char *table;
        unsigned int matchsize;
#ifdef CONFIG_COMPAT
        unsigned int compatsize;
#endif
        unsigned int hooks;
        unsigned short proto;

        unsigned short family;
};

/* Registration hooks for targets. */
struct xt_target {
        struct list_head list;

        const char name[XT_EXTENSION_MAXNAMELEN];
        u_int8_t revision;

        /* Returns verdict. Argument order changed since 2.6.9, as this
           must now handle non-linear skbs, using skb_copy_bits and
           skb_ip_make_writable. */
        unsigned int (*target)(struct sk_buff *skb,
                               const struct xt_action_param *);

        /* Called when user tries to insert an entry of this type:
           hook_mask is a bitmask of hooks from which it can be
           called. */
        /* Should return 0 on success or an error code otherwise (-Exxxx). */
        int (*checkentry)(const struct xt_tgchk_param *);

        /* Called when entry of this type deleted. */
        void (*destroy)(const struct xt_tgdtor_param *);
#ifdef CONFIG_COMPAT
        /* Called when userspace align differs from kernel space one */
        void (*compat_from_user)(void *dst, const void *src);
        int (*compat_to_user)(void __user *dst, const void *src);
#endif
        /* Set this to THIS_MODULE if you are a module, otherwise NULL */
        struct module *me;

        const char *table;
        unsigned int targetsize;
#ifdef CONFIG_COMPAT
        unsigned int compatsize;
#endif
        unsigned int hooks;
        unsigned short proto;

        unsigned short family;
};

/* Furniture shopping... */
struct xt_table {
        struct list_head list;

        /* What hooks you will enter on */
        unsigned int valid_hooks;

        /* Man behind the curtain... */
        struct xt_table_info *private;

        /* Set this to THIS_MODULE if you are a module, otherwise NULL */
        struct module *me;

        u_int8_t af;            /* address/protocol family */
        int priority;           /* hook order */

        /* A unique name... */
        const char name[XT_TABLE_MAXNAMELEN];
};

#include <linux/netfilter_ipv4.h>

/* The table itself */
struct xt_table_info {
        /* Size per table */
        unsigned int size;
        /* Number of entries: FIXME. --RR */
        unsigned int number;
        /* Initial number of entries. Needed for module usage count */
        unsigned int initial_entries;

        /* Entry points and underflows */
        unsigned int hook_entry[NF_INET_NUMHOOKS];
        unsigned int underflow[NF_INET_NUMHOOKS];

        /*
         * Number of user chains. Since tables cannot have loops, at most
         * @stacksize jumps (number of user chains) can possibly be made.
         */
        unsigned int stacksize;
        unsigned int __percpu *stackptr;
        void ***jumpstack;
        /* ipt_entry tables: one per CPU */
        /* Note : this field MUST be the last one, see XT_TABLE_INFO_SZ */
        void *entries[1];
};

#define XT_TABLE_INFO_SZ (offsetof(struct xt_table_info, entries) \
                          + nr_cpu_ids * sizeof(char *))
int xt_register_target(struct xt_target *target);
void xt_unregister_target(struct xt_target *target);
int xt_register_targets(struct xt_target *target, unsigned int n);
void xt_unregister_targets(struct xt_target *target, unsigned int n);

int xt_register_match(struct xt_match *target);
void xt_unregister_match(struct xt_match *target);
int xt_register_matches(struct xt_match *match, unsigned int n);
void xt_unregister_matches(struct xt_match *match, unsigned int n);

int xt_check_match(struct xt_mtchk_param *, unsigned int size, u_int8_t proto,
                   bool inv_proto);
int xt_check_target(struct xt_tgchk_param *, unsigned int size, u_int8_t proto,
                    bool inv_proto);

struct xt_table *xt_register_table(struct net *net,
                                   const struct xt_table *table,
                                   struct xt_table_info *bootstrap,
                                   struct xt_table_info *newinfo);
void *xt_unregister_table(struct xt_table *table);

struct xt_table_info *xt_replace_table(struct xt_table *table,
                                       unsigned int num_counters,
                                       struct xt_table_info *newinfo,
                                       int *error);

struct xt_match *xt_find_match(u8 af, const char *name, u8 revision);
struct xt_target *xt_find_target(u8 af, const char *name, u8 revision);
struct xt_match *xt_request_find_match(u8 af, const char *name, u8 revision);
struct xt_target *xt_request_find_target(u8 af, const char *name, u8 revision);
int xt_find_revision(u8 af, const char *name, u8 revision, int target,
                     int *err);

struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
                                    const char *name);
void xt_table_unlock(struct xt_table *t);

int xt_proto_init(struct net *net, u_int8_t af);
void xt_proto_fini(struct net *net, u_int8_t af);

struct xt_table_info *xt_alloc_table_info(unsigned int size);
void xt_free_table_info(struct xt_table_info *info);

/**
 * xt_recseq - recursive seqcount for netfilter use
 * 
 * Packet processing changes the seqcount only if no recursion happened
 * get_counters() can use read_seqcount_begin()/read_seqcount_retry(),
 * because we use the normal seqcount convention :
 * Low order bit set to 1 if a writer is active.
 */
DECLARE_PER_CPU(seqcount_t, xt_recseq);

/**
 * xt_write_recseq_begin - start of a write section
 *
 * Begin packet processing : all readers must wait the end
 * 1) Must be called with preemption disabled
 * 2) softirqs must be disabled too (or we should use this_cpu_add())
 * Returns :
 *  1 if no recursion on this cpu
 *  0 if recursion detected
 */
static inline unsigned int xt_write_recseq_begin(void)
{
        unsigned int addend;

        /*
         * Low order bit of sequence is set if we already
         * called xt_write_recseq_begin().
         */
        addend = (__this_cpu_read(xt_recseq.sequence) + 1) & 1;

        /*
         * This is kind of a write_seqcount_begin(), but addend is 0 or 1
         * We dont check addend value to avoid a test and conditional jump,
         * since addend is most likely 1
         */
        __this_cpu_add(xt_recseq.sequence, addend);
        smp_wmb();

        return addend;
}

/**
 * xt_write_recseq_end - end of a write section
 * @addend: return value from previous xt_write_recseq_begin()
 *
 * End packet processing : all readers can proceed
 * 1) Must be called with preemption disabled
 * 2) softirqs must be disabled too (or we should use this_cpu_add())
 */
static inline void xt_write_recseq_end(unsigned int addend)
{
        /* this is kind of a write_seqcount_end(), but addend is 0 or 1 */
        smp_wmb();
        __this_cpu_add(xt_recseq.sequence, addend);
}

/*
 * This helper is performance critical and must be inlined
 */
static inline unsigned long ifname_compare_aligned(const char *_a,
                                                   const char *_b,
                                                   const char *_mask)
{
        const unsigned long *a = (const unsigned long *)_a;
        const unsigned long *b = (const unsigned long *)_b;
        const unsigned long *mask = (const unsigned long *)_mask;
        unsigned long ret;

        ret = (a[0] ^ b[0]) & mask[0];
        if (IFNAMSIZ > sizeof(unsigned long))
                ret |= (a[1] ^ b[1]) & mask[1];
        if (IFNAMSIZ > 2 * sizeof(unsigned long))
                ret |= (a[2] ^ b[2]) & mask[2];
        if (IFNAMSIZ > 3 * sizeof(unsigned long))
                ret |= (a[3] ^ b[3]) & mask[3];
        BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
        return ret;
}

struct nf_hook_ops *xt_hook_link(const struct xt_table *, nf_hookfn *);
void xt_hook_unlink(const struct xt_table *, struct nf_hook_ops *);

#ifdef CONFIG_COMPAT
#include <net/compat.h>

struct compat_xt_entry_match {
        union {
                struct {
                        u_int16_t match_size;
                        char name[XT_FUNCTION_MAXNAMELEN - 1];
                        u_int8_t revision;
                } user;
                struct {
                        u_int16_t match_size;
                        compat_uptr_t match;
                } kernel;
                u_int16_t match_size;
        } u;
        unsigned char data[0];
};

struct compat_xt_entry_target {
        union {
                struct {
                        u_int16_t target_size;
                        char name[XT_FUNCTION_MAXNAMELEN - 1];
                        u_int8_t revision;
                } user;
                struct {
                        u_int16_t target_size;
                        compat_uptr_t target;
                } kernel;
                u_int16_t target_size;
        } u;
        unsigned char data[0];
};

/* FIXME: this works only on 32 bit tasks
 * need to change whole approach in order to calculate align as function of
 * current task alignment */

struct compat_xt_counters {
        compat_u64 pcnt, bcnt;                  /* Packet and byte counters */
};

struct compat_xt_counters_info {
        char name[XT_TABLE_MAXNAMELEN];
        compat_uint_t num_counters;
        struct compat_xt_counters counters[0];
};

struct _compat_xt_align {
        __u8 u8;
        __u16 u16;
        __u32 u32;
        compat_u64 u64;
};

#define COMPAT_XT_ALIGN(s) __ALIGN_KERNEL((s), __alignof__(struct _compat_xt_align))

void xt_compat_lock(u_int8_t af);
void xt_compat_unlock(u_int8_t af);

int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta);
void xt_compat_flush_offsets(u_int8_t af);
void xt_compat_init_offsets(u_int8_t af, unsigned int number);
int xt_compat_calc_jump(u_int8_t af, unsigned int offset);

int xt_compat_match_offset(const struct xt_match *match);
int xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
                              unsigned int *size);
int xt_compat_match_to_user(const struct xt_entry_match *m,
                            void __user **dstptr, unsigned int *size);

int xt_compat_target_offset(const struct xt_target *target);
void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
                                unsigned int *size);
int xt_compat_target_to_user(const struct xt_entry_target *t,
                             void __user **dstptr, unsigned int *size);

#endif /* CONFIG_COMPAT */
#endif /* _X_TABLES_H */
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