[sys net destiny]

- added dynamic calculation of round trip timeout (RTO)

projects/tlayer/main.c

@@ -265,7 +265,7 @@ void send_tcp_bulk(char *str)
 void send_tcp_bandwidth_test(char *str)
 	{
 	timex_t start, end, total;
-	uint32_t secs;
+	double secs;
 
 	int i = 0, count;
 	char command[80];
@@ -280,10 +280,9 @@ void send_tcp_bandwidth_test(char *str)
 		}
 	end = vtimer_now();
 	total = timex_sub(end, start);
-	secs = total.microseconds / 1000000;
+	secs = total.microseconds / 1000000.0f;
 	printf("Start: %lu, End: %lu, Total: %lu\n", start.microseconds, end.microseconds, total.microseconds);
-	secs = total.microseconds / 1000000;
-	printf("Time: %lu seconds, Bandwidth: %lu byte/second\n", secs, (count*48)/secs);
+	printf("Time: %f seconds, Bandwidth: %f byte/second\n", secs, (count*48)/secs);
 	}
 
 void connect_tcp(char *str)

sys/net/destiny/socket.c

@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <math.h>
 #include "udp.h"
 #include "tcp.h"
 #include "socket.h"
@@ -216,6 +217,7 @@ int bind_tcp_socket(int s, sockaddr6_t *name, int namelen, uint8_t pid)
 		}
 	memcpy(&getSocket(s)->socket_values.local_address, name, namelen);
 	getSocket(s)->recv_pid = pid;
+	getSocket(s)->socket_values.tcp_control.rto = TCP_INITIAL_ACK_TIMEOUT;
 	return 1;
 	}
 
@@ -587,6 +589,36 @@ int connect(int socket, sockaddr6_t *addr, uint32_t addrlen)
 	return 0;
 	}
 
+void calculate_rto(tcp_cb_t *tcp_control, timex_t current_time)
+	{
+	double rtt = timex_sub(current_time, tcp_control->last_packet_time).microseconds;
+	double srtt = tcp_control->srtt;
+	double rttvar = tcp_control->rttvar;
+	double rto = tcp_control->rto;
+
+	if ((srtt == 0) && (rttvar == 0) && (rto == TCP_INITIAL_ACK_TIMEOUT))
+		{
+		// First calculation
+		srtt = rtt;
+		rttvar = 0.5*rtt;
+		rto = rtt + 4*rttvar;
+		}
+	else
+		{
+		// every other calculation
+		srtt = (1-TCP_ALPHA)*srtt+TCP_ALPHA*rtt;
+		rttvar = (1-TCP_BETA)*rttvar+TCP_BETA*abs(srtt-rtt);
+		rto = srtt + (((4*rttvar) < TCP_TIMER_RESOLUTION) ? (TCP_TIMER_RESOLUTION) : (4*rttvar));
+		}
+	if (rto < SECOND)
+		{
+		rto = SECOND;
+		}
+	tcp_control->srtt = srtt;
+	tcp_control->rttvar = rttvar;
+	tcp_control->rto = rto;
+	}
+
 int32_t send(int s, void *msg, uint64_t len, int flags)
 	{
 	// Variables
@@ -690,6 +722,10 @@ int32_t send(int s, void *msg, uint64_t len, int flags)
 				{
 				case TCP_ACK:
 					{
+					if (current_tcp_socket->tcp_control.no_of_retries == 0)
+						{
+						calculate_rto(&current_tcp_socket->tcp_control, vtimer_now());
+						}
 					tcp_hdr_t *tcp_header = ((tcp_hdr_t*)(recv_msg.content.ptr));
 					if ((current_tcp_socket->tcp_control.send_nxt == tcp_header->ack_nr) && (total_sent_bytes == len))
 						{

sys/net/destiny/socket.h

@@ -158,6 +158,10 @@ typedef struct tcp_control_block
 
 	uint8_t 			state;
 
+	double				srtt;
+	double				rttvar;
+	double				rto;
+
 #ifdef TCP_HC
 	tcp_hc_context_t	tcp_context;
 #endif

sys/net/destiny/tcp_timer.c

@@ -50,7 +50,7 @@ void handle_synchro_timeout(socket_internal_t *current_socket)
 void handle_established(socket_internal_t *current_socket)
 	{
 	msg_t send;
-	uint32_t current_timeout = TCP_ACK_TIMEOUT;
+	uint32_t current_timeout = (uint32_t)(current_socket->socket_values.tcp_control.rto);
 	uint8_t i;
 	if ((current_socket->socket_values.tcp_control.send_nxt > current_socket->socket_values.tcp_control.send_una) &&
 			(thread_getstatus(current_socket->send_pid) == STATUS_RECEIVE_BLOCKED))
@@ -130,7 +130,7 @@ void inc_global_variables(void)
 void tcp_general_timer(void)
 	{
 	vtimer_t tcp_vtimer;
-	timex_t interval = timex_set(0, 500*1000);
+	timex_t interval = timex_set(0, TCP_TIMER_RESOLUTION);
 
 	while (1)
 		{

sys/net/destiny/tcp_timer.h

@@ -8,13 +8,18 @@
 #ifndef TCP_TIMER_H_
 #define TCP_TIMER_H_
 
-#define SECONDS						1000*1000
+#define TCP_TIMER_RESOLUTION		500*1000
+
+#define SECOND						1000*1000
 #define TCP_TIMER_STACKSIZE			2048
-#define TCP_SYN_INITIAL_TIMEOUT		6*SECONDS
-#define TCP_SYN_TIMEOUT				24*SECONDS
+#define TCP_SYN_INITIAL_TIMEOUT		6*SECOND
+#define TCP_SYN_TIMEOUT				24*SECOND
 #define TCP_MAX_SYN_RETRIES			3
-#define TCP_ACK_TIMEOUT				3*SECONDS 	// still static, should be calculated via RTT
-#define TCP_ACK_MAX_TIMEOUT			30*SECONDS 	// TODO: Set back to 90 Seconds
+#define TCP_INITIAL_ACK_TIMEOUT		3*SECOND 	// still static, should be calculated via RTT
+#define TCP_ACK_MAX_TIMEOUT			30*SECOND 	// TODO: Set back to 90 Seconds
+
+#define TCP_ALPHA					1.0f/8.0f
+#define TCP_BETA					1.0f/4.0f
 
 #define TCP_NOT_DEFINED				0
 #define TCP_RETRY					1