gbn.h

#ifndef _gbn_h
#define _gbn_h

#include<sys/types.h>
#include<sys/socket.h>
#include<sys/ioctl.h>
#include<signal.h>
#include<unistd.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<netinet/in.h>
#include<errno.h>
#include<netdb.h>
#include<time.h>
#include<assert.h>

/*----- Error variables -----*/
extern int h_errno;
extern int errno;

/*----- Protocol parameters -----*/
#define LOSS_PROB 1e-2    /* loss probability                            */
#define CORR_PROB 1e-3    /* corruption probability                      */
#define DATALEN   1024    /* length of the payload                       */
#define N         1024    /* Max number of packets a single call to gbn_send can process */
#define TIMEOUT      1    /* timeout to resend packets (1 second)        */


/*----- Packet types -----*/
#define SYN      0        /* Opens a connection                          */
#define SYNACK   1        /* Acknowledgement of the SYN packet           */
#define DATA     2        /* Data packets                                */
#define DATAACK  3        /* Acknowledgement of the DATA packet          */
#define FIN      4        /* Ends a connection                           */
#define FINACK   5        /* Acknowledgement of the FIN packet           */
#define RST      6        /* Reset packet used to reject new connections */

/*---- Actionable variables ----*/
#define MAX_ATTEMPTS 5
#define BACKLOG      1
#define TIMEOUT      1

/*----- Go-Back-n packet format -----*/
typedef struct {
    uint8_t  type;            /* packet type (e.g. SYN, DATA, ACK, FIN)     */
    uint32_t  seqnum;          /* sequence number of the packet              */
    uint16_t checksum;        /* header and payload checksum                */
    uint8_t data[DATALEN];    /* pointer to the payload                     */
    uint16_t actual_len;       /* actual data length in data field           */
} __attribute__((packed)) gbnhdr;

typedef struct state_t{

    int curr_state; /* ESTABLISHED, CLOSED, etc...*/
    uint32_t seq_num;  /* the current sequence number */
    uint8_t window_size; /* the current window size which should be reset to 1 when congestion */
    struct sockaddr address; /* the destination address */
    socklen_t sock_len; /* the size of the destination address */

} state_t;

enum {
    CLOSED=0,
    SYN_SENT,
    SYN_RCVD,
    ESTABLISHED,
    FIN_SENT,
    FIN_RCVD
};

extern state_t s;

void gbn_init();

uint8_t validate_packet(gbnhdr *packet);
gbnhdr *create_rcv_pkt();
void create_DATA_packet(gbnhdr *DATA_packet, uint32_t pkt_seqnum, \
            const void *buf_pointer, size_t data_len, int data_type);
void timeout_hdler(int);

int gbn_connect(int sockfd, const struct sockaddr *server, socklen_t socklen);
int gbn_listen(int sockfd, int backlog);
int gbn_bind(int sockfd, const struct sockaddr *server, socklen_t socklen);
int gbn_socket(int domain, int type, int protocol);
int gbn_accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
int gbn_close(int sockfd);
ssize_t gbn_send(int sockfd, const void *buf, size_t len, int flags);
ssize_t gbn_recv(int sockfd, void *buf, size_t len, int flags);

ssize_t  maybe_recvfrom(int  s, char *buf, size_t len, int flags, \
            struct sockaddr *from, socklen_t *fromlen);

uint16_t checksum(uint16_t *buf, int nwords);




#define h_addr h_addr_list[0] /* for backward compatibility */

#endif