int handle_cstate_est_send(mysocket_t sd, context_t * ctx){
//our_dprintf("*IN EST SEND\n");
size_t eff_wind = calc_eff_window(ctx);
size_t max_to_send = MIN(eff_wind, STCP_MSS);
if (max_to_send == 0) {
//our_dprintf("window too small to send min(%u, %u) \n", eff_wind, STCP_MSS);
return 0;
}
//our_dprintf("max to send %u\n", max_to_send);
/* receive data from app */
size_t recd_app;
uint8_t buff[max_to_send];
recd_app = stcp_app_recv(sd, buff, max_to_send);
/* construct header */
uint32_t header_size = sizeof(struct tcphdr);
uint8_t header_buf[header_size];
memset(header_buf, 0, header_size);
struct tcphdr * tcp_header = ( struct tcphdr *) header_buf;
tcp_header->th_seq = htonl(ctx->sent_last_byte_sent + 1);
tcp_header->th_flags |= TH_SYN;
tcp_header->th_off = 5; /* no options, data begins 20 bytes into packet */
/* set adv window size */
tcp_header->th_win = htons(calc_adv_wind(ctx));
ctx->sent_adv_window = calc_adv_wind(ctx);
/* copy the data into the tcp buffer */
uint32_t wind_index = ((ctx->sent_last_byte_written + 1)
- ctx->initial_sequence_num) % MAX_WINDOW_SIZE;
our_dprintf("window index %u\n", wind_index);
/* we're wrapping the buffer */
if (wind_index + recd_app > MAX_WINDOW_SIZE) {
size_t delta = MAX_WINDOW_SIZE - wind_index;
our_dprintf("wrapping the buffer\n");
/* fill the end of the buffer */
memcpy(ctx->send_wind + wind_index, buff, delta);
/* restart at the beginning of the buffer */
memcpy(ctx->send_wind, buff+delta, recd_app - delta);
stcp_network_send(sd, header_buf, header_size, ctx->send_wind + wind_index, delta,
ctx->send_wind, recd_app - delta, NULL);
} else {
/* don't need to wrap the buffer */
our_dprintf("not wrapping the buffer\n");
memcpy(ctx->send_wind + wind_index, buff, recd_app);
stcp_network_send(sd, header_buf, header_size, (ctx->send_wind + wind_index), recd_app, NULL);
}
ctx->sent_last_byte_sent += recd_app;
ctx->sent_last_byte_written += recd_app;
return 0;
}
static void transport_send_data(mysocket_t sd, char* data, int len, context_t* ctx)//LAN
{
strncpy(send_buffer, data);
ctx.next_seq += len;
ssize_t result = stcp_network_send(sd, send_buffer, sizeof(send_buffer), NULL);
//send real app data or stub data
}
/* ***************************************************
* Function: network_send
* ***************************************************
* Wrapper function for sending network data. It converts header fields
* into network byte-order but then changes them back before returning
* in case the caller plans to use that packet later on.
*/
ssize_t network_send(mysocket_t sd, const void *src, size_t src_len)
{
struct tcphdr* hdr = (struct tcphdr *)src;
hdr->th_ack = htonl(hdr->th_ack);
hdr->th_seq = htonl(hdr->th_seq);
hdr->th_win = htons(hdr->th_win);
hdr->th_flags = hdr->th_flags;
hdr->th_off = hdr->th_off;
ssize_t result;
while ((result = stcp_network_send(sd, src, src_len, NULL))<0);
hdr->th_ack = ntohl(hdr->th_ack);
hdr->th_seq = ntohl(hdr->th_seq);
hdr->th_win = ntohs(hdr->th_win);
return result;
}
static void transport_send_head(mysocket_t sd, int hflag, context_t* ctx)//LAN
{
struct tcphdr head;
//fill a ACK header
head.th_flags = hflag;
head.th_seq = ;//unsent seq number
head.th_ack = ctx->next_seq;//ctx->next_seq;
head.th_win = ;//???
head.th_seq = htons(head.th_seq);
head.th_ack = htons(head.th_ack);
head.th_win = htons(head.th_win);
ssize_t result = stcp_network_send(sd, send_buffer, sizeof(struct tcphdr), NULL);
//use htonl htons to codec
}
int send_syn_ack_fin(mysocket_t sd, context_t * ctx, uint8_t to_send_flags,
tcp_seq seq_num, tcp_seq ack_num) {
size_t len = sizeof(struct tcphdr);
uint8_t buff[len];
struct tcphdr * tcp_packet = (struct tcphdr *) buff;
/* th_sport, th_dport, th_sum are set by network layer */
/* th_urg is ignored by stcp*/
if (to_send_flags & SEND_SYN) {
tcp_packet->th_seq = htonl(seq_num);
tcp_packet->th_flags |= TH_SYN;
ctx->sent_last_byte_written = seq_num;
ctx->sent_last_byte_sent = seq_num;
} else {
tcp_packet->th_seq = htonl(ctx->sent_last_byte_sent + 1);
}
if (to_send_flags & SEND_ACK) {
tcp_packet->th_ack = htonl(ack_num);
tcp_packet->th_flags |= TH_ACK;
//our_dprintf("sending ack %u\n", ack_num);
}
if (to_send_flags & SEND_FIN) {
tcp_packet->th_flags |= TH_FIN;
ctx->sent_last_byte_sent++;
ctx->sent_last_byte_written++;
}
tcp_packet->th_off = 5; /* no options, data begins 20 bytes into packet */
/* set adv window size */
tcp_packet->th_win = htons(calc_adv_wind(ctx));
ctx->sent_adv_window = calc_adv_wind(ctx);
/* send the newly constructed packet */
ssize_t n = stcp_network_send(sd, buff , len, 0);
if (n == -1){
fprintf(stderr,"error: client bad send\n");
return -1;
}
return 0;
}
/* control_loop() is the main STCP loop; it repeatedly waits for one of the
* following to happen:
* - incoming data from the peer
* - new data from the application (via mywrite())
* - the socket to be closed (via myclose())
* - a timeout
*/
static void control_loop(mysocket_t sd, context_t *ctx)
{
assert(ctx);
int tcplen;
char payload[MAXLEN];
STCPHeader *in_header;
void *packtosend;
char *indicpt;
char tempbuff[WINLEN];
stcp_event_type_t eventflag;
while (!ctx->done)
{
unsigned int event;
eventflag = ANY_EVENT;
/* set timeout if there is any unack'd data; if not, just make it NULL */
struct timespec timestart;
struct timespec *timeout;
if (ctx->send_unack < ctx->send_next) {
timestart = ((packet_t *)list_get_at(ctx->unackd_packets, 0))->start_time;
timeout = ×tart;
/* constructs the timeout with absolute time by adding the RTO */
timeout->tv_sec += ctx->rto.tv_sec;
timeout->tv_nsec += ctx->rto.tv_nsec;
/* ensures no nanosecond overflow */
if (timeout->tv_nsec >= 1000000000) {
timeout->tv_sec += timeout->tv_nsec / 1000000000;
timeout->tv_nsec = timeout->tv_nsec % 1000000000;
}
if (timeout->tv_sec <= time(NULL))
/*earliest unacked packet has timed out, unless it's currently sitting in buffer */
eventflag = NETWORK_DATA|TIMEOUT;
}
else {
timeout = NULL;
DEBUG("No timeout set\n");
}
/* see stcp_api.h or stcp_api.c for details of this function */
/* XXX: you will need to change some of these arguments! */
event = stcp_wait_for_event(sd, eventflag, timeout);
/* check whether it was the network, app, or a close request */
if (event & APP_DATA)
{
DEBUG("Application Data\n");
/* the application has requested that data be sent */
/* we should send as long as send_wind > 0 */
int open_window = ctx->send_wind - (ctx->send_next - ctx->send_unack);
if(open_window > 0)
{
int send_size;
/* only read in as much from app as we can send */
if(open_window > MAXLEN) send_size = MAXLEN;
else send_size = open_window;
void* buffer = (char *) calloc(1, send_size);
tcplen = stcp_app_recv(sd, buffer, send_size);
if( tcplen > 0 ) {
DEBUG("Application data size: %d\n", tcplen);
/*create and send packet*/
packtosend = (void *)make_stcp_packet(TH_ACK, ctx->send_next, ctx->recv_next, tcplen);
memcpy(packtosend + sizeof(STCPHeader), buffer, tcplen);
stcp_network_send(sd, packtosend, sizeof(STCPHeader) + tcplen, NULL);
DEBUG("Packet of payload size %d, ack number %d, seq number %d sent to network\n", tcplen, ctx->recv_next, ctx->send_next);
packet_t_create(ctx, packtosend, sizeof(STCPHeader) + tcplen); /* now a packet has been pushed onto the unacked queue */
/* update window length and send_next */
ctx->send_next += tcplen;
}
free(buffer);
buffer = NULL;
free(packtosend);
packtosend = NULL;
}
else DEBUG("Could not get application data\n");
}
if (event & NETWORK_DATA)
{
DEBUG("Network Data\n");
in_header = malloc(sizeof(STCPHeader));
/* network data transmission */
int data_size = recv_packet(sd, ctx, payload, MAXLEN, in_header);
DEBUG("Received net data size is %d\n", data_size);
/* send ACK as long as it's not past our window, and actually contained data */
if(data_size > 0 || data_size == -2) { /* -2 indicates it received old data, which we should not send to the application */
packtosend = (void *)make_stcp_packet(TH_ACK, ctx->send_next, ctx->recv_next, 0);
stcp_network_send(sd, packtosend, sizeof(STCPHeader), NULL);
free(packtosend);
packtosend = NULL;
}
/* send payload to application, if it's valid */
if(data_size > 0) {
DEBUG("Sent data of size %d to application\n", data_size);
stcp_app_send(sd, ctx->recv_buffer, data_size);
/* slide the window over */
indicpt = strchr(ctx->recv_indicator, '\0');
data_size = indicpt - ctx->recv_indicator;
memcpy(tempbuff, ctx->recv_buffer + data_size, WINLEN - data_size);
memset(ctx->recv_buffer, '\0', WINLEN);
memcpy(ctx->recv_buffer, tempbuff, WINLEN - data_size);
/* slide window indicator over */
memcpy(tempbuff, indicpt, WINLEN - data_size);
memset(ctx->recv_indicator, '\0', WINLEN);
memcpy(ctx->recv_indicator, tempbuff, WINLEN - data_size);
}
/* deal with connection teardown, if need be */
if (in_header->th_flags & TH_ACK) {
/* go from FIN-WAIT1 --> FIN-WAIT2 */
if(ctx->connection_state == CSTATE_FIN_WAIT1) {
DEBUG("State: FIN-WAIT2\n");
ctx->connection_state = CSTATE_FIN_WAIT2;
}
/* go from LAST-ACK --> CLOSED */
if(ctx->connection_state == CSTATE_LAST_ACK) {
DEBUG("State: CLOSED\n");
ctx->connection_state = CSTATE_CLOSED;
free(in_header);
in_header = NULL;
break;
}
/* go from CLOSING --> CLOSED */
if(ctx->connection_state == CSTATE_CLOSING) {
DEBUG("State: CLOSED\n");
ctx->connection_state = CSTATE_CLOSED;
free(in_header);
in_header = NULL;
break;
}
}
/* branching for the receipt of a FIN packet */
if (in_header->th_flags & TH_FIN) {
DEBUG("Received FIN packet\n");
/* Acknowledge FIN, which counts as a byte */
ctx->recv_next++;
packtosend = (void *)make_stcp_packet(TH_ACK, ctx->send_next, ctx->recv_next, 0);
stcp_network_send(sd, packtosend, sizeof(STCPHeader), NULL);
/* go into CLOSE-WAIT */
if (ctx->connection_state == CSTATE_ESTABLISHED) {
DEBUG("State: CLOSE_WAIT\n");
/* inform app of FIN */
stcp_fin_received(sd);
ctx->connection_state = CSTATE_CLOSE_WAIT;
}
/* go from FIN-WAIT2 --> CLOSED */
if (ctx->connection_state == CSTATE_FIN_WAIT2) {
DEBUG("State: CLOSED\n");
ctx->connection_state = CSTATE_CLOSED;
free(in_header);
in_header = NULL;
break;
}
/* go from FIN-WAIT1 --> CLOSING */
if (ctx->connection_state == CSTATE_FIN_WAIT1) {
DEBUG("State: CLOSING\n");
/* inform app of FIN */
stcp_fin_received(sd);
ctx->connection_state = CSTATE_CLOSING;
}
free(in_header);
in_header = NULL;
}
}
if (event & APP_CLOSE_REQUESTED)
{
DEBUG("Application close requested\n");
if(ctx->connection_state == CSTATE_ESTABLISHED)
{
/* need to send all outstanding data first */
DEBUG("Sending FIN packet with seq %d, ack %d\n", ctx->send_next, ctx->recv_next);
STCPHeader *header = make_stcp_packet(TH_FIN, ctx->send_next, ctx->recv_next, 0);
stcp_network_send(sd, header, sizeof(STCPHeader), NULL);
ctx->send_unack += 1;
packet_t_create(ctx, header, sizeof(STCPHeader));
free(header);
header = NULL;
/* go into FIN-WAIT1 */
ctx->connection_state = CSTATE_FIN_WAIT1;
DEBUG("State: FIN-WAIT1\n");
}
if(ctx->connection_state == CSTATE_CLOSE_WAIT)
{
DEBUG("Sending FIN packet with seq %d, ack %d\n", ctx->send_next, ctx->recv_next);
STCPHeader *header = make_stcp_packet(TH_FIN, ctx->send_next, ctx->recv_next, 0);
stcp_network_send(sd, header, sizeof(STCPHeader), NULL);
packet_t_create(ctx, header, sizeof(STCPHeader));
ctx->send_next += 1;
free(header);
header = NULL;
/* go from CLOSE-WAIT --> LAST-ACK */
ctx->connection_state = CSTATE_LAST_ACK;
DEBUG("State: LAST-ACK\n");
}
}
if (event == TIMEOUT)
{
int giveup = 0;
/* TIMEOUT--resend all packets in ctx->unackd_packets */
packet_t *resendpack;
list_iterator_start(ctx->unackd_packets);
while (list_iterator_hasnext(ctx->unackd_packets)) {
resendpack = (packet_t *)list_iterator_next(ctx->unackd_packets);
if (resendpack->retry_count > 6) {
/*close the connection*/
DEBUG("Too many retries");
errno = ECONNABORTED;
giveup = 1;
}
/* increment retries */
resendpack->retry_count++;
clock_gettime(CLOCK_REALTIME, &(resendpack->start_time));
((STCPHeader *)(resendpack->packet))->th_ack = htonl(ctx->recv_next);
stcp_network_send(sd, resendpack->packet, resendpack->packet_size, NULL);
DEBUG("Resent packet with sequence number %d\n", ntohl(((STCPHeader *)(resendpack->packet))->th_seq));
}
list_iterator_stop(ctx->unackd_packets);
if (giveup)
break;
}
}
}
/* initialise the transport layer, and start the main loop, handling
* any data from the peer or the application. this function should not
* return until the connection is closed.
*/
void transport_init(mysocket_t sd, bool_t is_active)
{
context_t *ctx;
uint8_t flags;
int tcplen;
ctx = (context_t *) calloc(1, sizeof(context_t));
assert(ctx);
/* ensures this array begins as entirely null characters */
memset(ctx->recv_indicator, '\0', WINLEN);
char buffer[sizeof(STCPHeader) + MAXLEN];
generate_initial_seq_num(ctx);
ctx->connection_state = CSTATE_CLOSED;
list_t unackd;
ctx->unackd_packets = &unackd;
list_init(ctx->unackd_packets);
/* used for setting timeouts */
struct timespec timestart;
struct timespec *timeout;
/* XXX: you should send a SYN packet here if is_active, or wait for one
* to arrive if !is_active. after the handshake completes, unblock the
* application with stcp_unblock_application(sd). you may also use
* this to communicate an error condition back to the application, e.g.
* if connection fails; to do so, just set errno appropriately (e.g. to
* ECONNREFUSED, etc.) before calling the function.
*/
if(is_active)
{
ctx->send_unack = ctx->initial_sequence_num;
STCPHeader *header = make_stcp_packet(TH_SYN, ctx->send_unack, 0, 0);
/* first step in the handshake: sending a SYN packet */
tcplen = stcp_network_send(sd, header, sizeof(STCPHeader), NULL);
ctx->send_next = ctx->send_unack;
/* this ensures the SYN packet will be resent if it is dropped/times out */
packet_t_create(ctx, header, sizeof(STCPHeader));
DEBUG("Sent SYN packet with seq number %d\n", ntohl(header->th_seq));
if(tcplen < 0) {
DEBUG("SYN send failed");
errno = ECONNREFUSED;
}
else
{
ctx->send_next++;
ctx->connection_state = CSTATE_SYN_SENT;
/* the client now waits for a SYN/ACK */
while(ctx->connection_state == CSTATE_SYN_SENT)
{
timestart = ((packet_t *)list_get_at(ctx->unackd_packets, 0))->start_time;
timeout = ×tart;
timeout->tv_sec += ctx->rto.tv_sec;
timeout->tv_nsec += ctx->rto.tv_nsec;
if (timeout->tv_nsec >= 1000000000) {
timeout->tv_sec += timeout->tv_nsec / 1000000000;
timeout->tv_nsec = timeout->tv_nsec % 1000000000;
}
unsigned int event = stcp_wait_for_event(sd, NETWORK_DATA, timeout); /* yes we need to add timeout later */
if(event & NETWORK_DATA)
{
/* we now expect the next packet to be a SYN-ACK */
tcplen = recv_packet(sd, ctx, NULL, 0, header);
flags = (TH_SYN|TH_ACK);
if( tcplen < 0 || !((header->th_flags & TH_SYN)&&(header->th_flags & TH_ACK))) {
DEBUG("Did not receive SYN/ACK\n");
continue;
}
else
{
DEBUG("packet received with seq %d and ack %d\n", ntohl(header->th_seq), ntohl(header->th_ack));
if(ntohl(header->th_ack) == ctx->send_next) {
header = make_stcp_packet(TH_ACK, ctx->send_next, ctx->recv_next, 0);
tcplen = stcp_network_send(sd, header, sizeof(STCPHeader), NULL);
/* the client now sends an ACK packet, and goes to the ESTABLISHED state */
DEBUG("Sent ACK packet with seq number %d\n", ntohl(header->th_seq));
if(tcplen < 0) {
DEBUG("ACK send failed");
errno = ECONNABORTED;
break;
}
ctx->connection_state = CSTATE_ESTABLISHED;
free(header);
header = NULL;
}
}
}
}
}
}
if(!is_active)
{
/* wait for a SYN packet */
while(ctx->connection_state == CSTATE_CLOSED)
{
ctx->send_unack = ctx->initial_sequence_num;
ctx->send_next = ctx->send_unack;
unsigned int event = stcp_wait_for_event(sd, NETWORK_DATA|TIMEOUT, NULL);
if(event & NETWORK_DATA) {
STCPHeader *header = (STCPHeader *) malloc(sizeof(STCPHeader));
tcplen = recv_packet(sd, ctx, NULL, 0, header);
if(tcplen < 0 || header->th_flags != TH_SYN) {
DEBUG("Did not receive SYN packet\n");
continue;
}
else
{
DEBUG("Received SYN with seq number %d\n", ntohl(header->th_seq));
ctx->connection_state = CSTATE_SYN_RECEIVED;
header = make_stcp_packet(TH_SYN|TH_ACK, ctx->send_unack, ctx->recv_next, 0);
tcplen = stcp_network_send(sd, header, sizeof(STCPHeader), NULL);
packet_t_create(ctx, header, sizeof(STCPHeader));
/* send out a SYN/ACK packet to the initiating client */
DEBUG("SYN/ACK sent with ack number %d and seq number %d\n", htonl(header->th_ack), htonl(header->th_seq));
if(tcplen < 0) {
DEBUG("SYN/ACK send failed");
errno = ECONNABORTED;
break;
}
/* ensures the SYN-ACK will be resent if it is not ACK'd */
packet_t_create(ctx, header, sizeof(STCPHeader));
ctx->send_next++;
}
}
}
while(ctx->connection_state == CSTATE_SYN_RECEIVED)
{
timestart = ((packet_t *)list_get_at(ctx->unackd_packets, 0))->start_time;
timeout = ×tart;
timeout->tv_sec += ctx->rto.tv_sec;
timeout->tv_nsec += ctx->rto.tv_nsec;
if (timeout->tv_nsec >= 1000000000) {
timeout->tv_sec += timeout->tv_nsec / 1000000000;
timeout->tv_nsec = timeout->tv_nsec % 1000000000;
}
unsigned int event = stcp_wait_for_event(sd, NETWORK_DATA, timeout);
if(event & NETWORK_DATA) {
STCPHeader *header = (STCPHeader *) buffer;
tcplen = recv_packet(sd, ctx, NULL, 0, header);
if(tcplen < 0 || !(header->th_flags & TH_ACK)) {
DEBUG("Did not receive ACK packet\n");
continue;
}
/* if it's the right ACK packet, go to the ESTABLISHED state */
if(ntohl(header->th_ack) == ctx->send_next) {
DEBUG("Received ACK with ack number %d\n", ntohl(header->th_ack));
ctx->connection_state = CSTATE_ESTABLISHED;
}
}
}
}
if(ctx->connection_state == CSTATE_ESTABLISHED)
DEBUG("State: seq %d ack %d send window %d\n", ctx->send_next, ctx->recv_next, ctx->send_wind);
/* unblocks the application */
/* relays possible error conditions */
stcp_unblock_application(sd);
control_loop(sd, ctx);
/* do any cleanup here */
free(ctx);
}
