store the time a client connected.

src/main.c

@@ -936,6 +936,7 @@ fork_failed:
 					ctmp->remote_addr_len = ws.remote_addr_len;
 
 					ctmp->pid = pid;
+					ctmp->conn_time = time(0);
 					ctmp->fd = cmd_fd[0];
 					set_cloexec_flag (cmd_fd[0], 1);
 

src/main.h

@@ -77,6 +77,8 @@ struct proc_st {
 	pid_t pid;
 	time_t udp_fd_receive_time; /* when the corresponding process has received a UDP fd */
 	
+	time_t conn_time; /* the time the user connected */
+
 	/* the tun lease this process has */
 	struct tun_lease_st tun_lease;
 	struct ip_lease_st *ipv4;