#ifndef _CONNTRACK_PROTO_GRE_H
#define _CONNTRACK_PROTO_GRE_H
#include <asm/byteorder.h>

/* GRE PROTOCOL HEADER */

/* GRE Version field */
#define GRE_VERSION_1701        0x0
#define GRE_VERSION_PPTP        0x1

/* GRE Protocol field */
#define GRE_PROTOCOL_PPTP       0x880B

/* GRE Flags */
#define GRE_FLAG_C              0x80
#define GRE_FLAG_R              0x40
#define GRE_FLAG_K              0x20
#define GRE_FLAG_S              0x10
#define GRE_FLAG_A              0x80

#define GRE_IS_C(f)     ((f)&GRE_FLAG_C)
#define GRE_IS_R(f)     ((f)&GRE_FLAG_R)
#define GRE_IS_K(f)     ((f)&GRE_FLAG_K)
#define GRE_IS_S(f)     ((f)&GRE_FLAG_S)
#define GRE_IS_A(f)     ((f)&GRE_FLAG_A)

/* GRE is a mess: Four different standards */
struct gre_hdr {
#if defined(__LITTLE_ENDIAN_BITFIELD)
        __u16        rec:3,
                srr:1,
                seq:1,
                key:1,
                routing:1,
                csum:1,
                version:3,
                reserved:4,
                ack:1;
#elif defined(__BIG_ENDIAN_BITFIELD)
        __u16        csum:1,
                routing:1,
                key:1,
                seq:1,
                srr:1,
                rec:3,
                ack:1,
                reserved:4,
                version:3;
#else
#error "Adjust your <asm/byteorder.h> defines"
#endif
        __u16        protocol;
};

/* modified GRE header for PPTP */
struct gre_hdr_pptp {
        __u8  flags;                /* bitfield */
        __u8  version;                /* should be GRE_VERSION_PPTP */
        __u16 protocol;                /* should be GRE_PROTOCOL_PPTP */
        __u16 payload_len;        /* size of ppp payload, not inc. gre header */
        __u16 call_id;                /* peer's call_id for this session */
        __u32 seq;                /* sequence number.  Present if S==1 */
        __u32 ack;                /* seq number of highest packet recieved by */
                                /*  sender in this session */
};

/* this is part of ip_conntrack */
struct ip_ct_gre {
        unsigned int stream_timeout;
        unsigned int timeout;
};

/* this is part of ip_conntrack_expect */
struct ip_ct_gre_expect {
        struct ip_ct_gre_keymap *keymap_orig, *keymap_reply;
};

#ifdef __KERNEL__

/* structure for original <-> reply keymap */
struct ip_ct_gre_keymap {
        struct list_head list;

        struct ip_conntrack_tuple tuple;
        struct ip_conntrack_expect *master;
};

/* add new tuple->key_reply pair to keymap */
int ip_ct_gre_keymap_add(struct ip_conntrack_expect *exp,
                         struct ip_conntrack_tuple *t,
                         int reply);

/* change an existing keymap entry */
void ip_ct_gre_keymap_change(struct ip_ct_gre_keymap *km,
                             struct ip_conntrack_tuple *t);

/* get pointer to gre key, if present */
static inline u_int32_t *gre_key(struct gre_hdr *greh)
{
        if (!greh->key)
                return NULL;
        if (greh->csum || greh->routing)
                return (u_int32_t *) (greh+sizeof(*greh)+4);
        return (u_int32_t *) (greh+sizeof(*greh));
}

/* get pointer ot gre csum, if present */
static inline u_int16_t *gre_csum(struct gre_hdr *greh)
{
        if (!greh->csum)
                return NULL;
        return (u_int16_t *) (greh+sizeof(*greh));
}

#endif /* __KERNEL__ */

#endif /* _CONNTRACK_PROTO_GRE_H */