static void parse_message(char *msg)
{
char *label = msg;
char *value = strchr(label, ' ');
char *cksum;
if (!value) {
fprintf(stderr, "Did not find value in message \"%s\"\n", msg);
return;
}
*value = 0;
value++;
cksum = strchr(value, ' ');
if (!cksum) {
fprintf(stderr, "Did not find cksum in message \"%s\"\n", msg);
return;
}
*cksum = 0;
cksum++;
if (*cksum != compute_cksum(label, value)) {
fprintf(stderr, "%s %s has cksum %c, invalid on the wire.\n", label, value, *cksum);
return;
} else {
// fprintf(stderr, "%s %s has valid cksum %c\n", label, value, *cksum);
accumulate_value(label, value);
}
}
int send_final_close_ack(uint32_t source_port, int portno, int sockfd)
{
int num_sent;
struct tcp_hdr close_req_seg;
char tcp_char_seg[255];
unsigned short int cksum_arr[12];
close_req_seg.src = source_port; //set source port
close_req_seg.des = portno; //set destination port
close_req_seg.seq = 0; //Assign an initial client sequence number with
close_req_seg.ack = 0; //a zero acknowledgement number
close_req_seg.hdr_flags = FIN; //set the FIN bit to 1
close_req_seg.rec = 0;
close_req_seg.cksum = 0;
close_req_seg.ptr = 0;
close_req_seg.opt = 0;
memcpy(cksum_arr, &close_req_seg, 24);
close_req_seg.cksum = compute_cksum(cksum_arr);
printf("-----CLOSE ACKNOWLEDGEMENT TO SERVER-----\n");
print_tcp_seg(&close_req_seg);
memcpy(tcp_char_seg, &close_req_seg, sizeof close_req_seg);
num_sent = write(sockfd, tcp_char_seg, 255);
if (num_sent < 0)
{
printf("error writing to socket...\n");
return 1;
}
return 0;
}
int send_conn_request(uint32_t source_port, int portno, int sockfd)
{
int num_sent;
struct tcp_hdr tcp_seg;
unsigned short int cksum_arr[12];
char tcp_char_segment[255];
/*set up connection request tcp struct*/
tcp_seg.src = source_port; //set source port
tcp_seg.des = portno; //set destination port
tcp_seg.seq = CLIENT_SEQ; //Assign an initial client sequence number with
tcp_seg.ack = 0; //a zero acknowledgement number
tcp_seg.hdr_flags = SYN; //set the SYN bit to 1
tcp_seg.rec = 0;
tcp_seg.cksum = 0;
tcp_seg.ptr = 0;
tcp_seg.opt = 0;
memcpy(cksum_arr, &tcp_seg, 24); //Copying 24 bytes
tcp_seg.cksum = compute_cksum(cksum_arr); //compute checksum
printf("-----TRANSMITTED CONNECTION REQUEST SEGMENT-----\n");
print_tcp_seg(&tcp_seg);
/* send TCP struct to server */
memcpy(tcp_char_segment, &tcp_seg, sizeof(tcp_seg)); //copy struct to char array
num_sent = write(sockfd, tcp_char_segment, 255); //write to socket
if (num_sent < 0)
{
printf("error writing to socket...\n");
exit(1);
}
return 0;
}
int send_ack_tcp_seg(int sockfd)
{
int num_recv, num_sent, temp_portno;
char tcp_char_seg[255];
unsigned short int cksum_arr[12];
struct tcp_hdr conn_grant_seg;
/* read in connection granted segment */
num_recv = read(sockfd, tcp_char_seg, 255); //read from socket
if(num_recv < 0)
{
printf("error reading from socket...\n");
exit(1);
}
memcpy(&conn_grant_seg, tcp_char_seg, sizeof conn_grant_seg); //copy buffer to segment
printf("-----RECEIVED CONNECTION GRANTED SEGMENT-----\n");
print_tcp_seg(&conn_grant_seg);
//swap port numbers
temp_portno = conn_grant_seg.src;
conn_grant_seg.src = conn_grant_seg.des;
conn_grant_seg.des = temp_portno;
//Assign a sequence number as initial client sequence number + 1 with an acknowledgement number equal to initial server sequence number + 1
conn_grant_seg.ack = conn_grant_seg.seq + 1; //201
//Set the ACK bit to 1
conn_grant_seg.hdr_flags = ACK;
//Compute the 16-bit checksum of the entire TCP segment and populate the checksum field
memcpy(cksum_arr, &conn_grant_seg, 24);
conn_grant_seg.cksum = compute_cksum(cksum_arr);
//respond to server with acknowledgent TCP segment
bzero(tcp_char_seg,255);
memcpy(tcp_char_seg, &conn_grant_seg, sizeof conn_grant_seg);
printf("-----TRANSMITTED ACKNOWLEDGEMENT SEGMENT-----\n");
print_tcp_seg(&conn_grant_seg);
num_sent = write(sockfd, tcp_char_seg, 255); //write back to server
if (num_sent < 0)
{
printf("error writing to socket...\n");
exit(1);
}
return 0;
}
static void run_reset_resident(void)
{
const struct rrcode *p = (const struct rrcode *)phystop;
for (--p; p > (struct rrcode *)&etv_timer; p--)
{
if (p->magic != RR_MAGIC)
continue;
if (p->pointer != p)
continue;
if (compute_cksum((const UWORD *)p) != RR_CHKSUM)
continue;
regsafe_call(p->program);
}
}
int send_close_req(uint32_t source_port, int portno, int sockfd)
{
int num_sent, num_recv;
struct tcp_hdr close_req_seg;
struct tcp_hdr close_ack_seg;
char tcp_char_seg[255];
unsigned short int cksum_arr[12];
close_req_seg.src = source_port; //set source port
close_req_seg.des = portno; //set destination port
close_req_seg.seq = CLIENT_SEQ; //Assign an initial client sequence number with
close_req_seg.ack = 0; //a zero acknowledgement number
close_req_seg.hdr_flags = FIN; //set the FIN bit to 1
close_req_seg.rec = 0;
close_req_seg.cksum = 0;
close_req_seg.ptr = 0;
close_req_seg.opt = 0;
memcpy(cksum_arr, &close_req_seg, 24);
close_req_seg.cksum = compute_cksum(cksum_arr);
printf("-----TRANSMITTED CLOSE REQUEST-----\n");
print_tcp_seg(&close_req_seg);
memcpy(tcp_char_seg, &close_req_seg, sizeof close_req_seg);
num_sent = write(sockfd, tcp_char_seg, 255);
if (num_sent < 0)
{
printf("error writing to socket...\n");
return 1;
}
/* read in close acknowledge segment */
bzero(tcp_char_seg, 255);
num_recv = read(sockfd, tcp_char_seg, 255); //read from socket
if(num_recv < 0)
{
printf("error reading from socket...\n");
exit(1);
}
memcpy(&close_ack_seg, tcp_char_seg, sizeof close_ack_seg); //copy buffer to segment
printf("-----CLOSE ACK SEGMENT FROM SERVER-----\n");
print_tcp_seg(&close_ack_seg);
/* read in second close acknowledge segment */
bzero(tcp_char_seg, 255);
num_recv = read(sockfd, tcp_char_seg, 255); //read from socket
if(num_recv < 0)
{
printf("error reading from socket...\n");
exit(1);
}
memcpy(&close_ack_seg, tcp_char_seg, sizeof close_ack_seg); //copy buffer to segment
close_ack_seg.hdr_flags = ACK;
close_ack_seg.ack = close_ack_seg.seq;
printf("-----SECOND CLOSE ACK SEGMENT FROM SERVER-----\n");
print_tcp_seg(&close_ack_seg);
return 0;
}
