tcp.h

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/* TCP handling code.
 *
 */

#ifndef _TCP_H
#define _TCP_H

#include "tcpproxy.h"

#define TCP_PROTO          6
#define IP_VERSION         4
#define IP_START_TTL       254   /* TTL for spoofed packets from proxy, e.g. TCP RST. */
#define TCP_LINK_MSS       1402  /* MSS of the GPRS link in bytes. */
#define TCP_TWO_MSL        60000 /* Twice maximum segment lifetime, in milliseconds.  */
#define TCP_WIN_CLAMP_SIZE 12618 /* TCP window size to clamp to (9 * MSS). */

typedef struct tcp_cid
{
    /* Values stored in network byte order. */
    __u32 saddr;
    __u32 daddr;            
    __u16 sport;
    __u16 dport;                
} Ttcp_cid;

/* NB: Remember to modify tcp_switch in tcp.c if tcp_state is modified. */
typedef enum tcp_state
{
    TCPS_FREE = 0,
    TCPS_NEW,
    TCPS_SYN_SENT,
    TCPS_SYN_RECV,
    TCPS_ESTABLISHED,
    TCPS_FIN_WAIT1,
    TCPS_FIN_WAIT2,
    TCPS_TIME_WAIT,
    TCPS_CLOSED,
    TCPS_CLOSE_WAIT,
    TCPS_LAST_ACK,
    TCPS_CLOSING,
    TCPS_MAX_STATES
} Ttcp_state;

enum {
    TCP_INIT_MH_SEQ = 1,
    TCP_INIT_MH_ACK = 2,
    TCP_INIT_FH_SEQ = 4,
    TCP_INIT_FH_ACK = 8
};

typedef struct tcp_cb
{
    /* Value of cid must be such that saddr is that of the host on proxied link 
     * (e.g. the mobile host).
     */
    struct tcp_cid cid;
    enum tcp_state state;  /* State is that of the mobile host's TCP.        */
    unsigned init;         /* Bits to indicate initialised parts of state.   */
    unsigned mh_seq;       /* Current sequence number from MH (seq+segsize). */
    unsigned mh_ack;       /* Highest ack received from MH.                  */
    unsigned fh_seq;       /* Current sequence number from FH (seq+segsize). */
    unsigned fh_ack;       /* Highest ack received from FG.                  */
    int out_queue;         /* Number of tcp output queue.                    */
    pthread_mutex_t mut;   /* Mutex for synchronisation.                     */
} Ttcp_cb;


void init_tcp();
void cleanup_tcp();
inline int seq_cmp(unsigned a, unsigned b);
inline int tcp_data_size(Tpacket_data *pd);
void tcp_timeout(void *ptr);
int handle_tcp(Tpacket_data *pd);

#endif /* _TCP_H */

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