x_tables.h

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#ifndef _X_TABLES_H
#define _X_TABLES_H


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

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 {
    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_mtdtor_param {
    struct net *net;
    const struct xt_match *match;
    void *matchinfo;
    u_int8_t family;
};

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 *))
extern int xt_register_target(struct xt_target *target);
extern void xt_unregister_target(struct xt_target *target);
extern int xt_register_targets(struct xt_target *target, unsigned int n);
extern void xt_unregister_targets(struct xt_target *target, unsigned int n);

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

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

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

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

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

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

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

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

DECLARE_PER_CPU(seqcount_t, xt_recseq);

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;
}

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;
}

extern struct nf_hook_ops *xt_hook_link(const struct xt_table *, nf_hookfn *);
extern 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))

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

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

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

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