Modify data-xfer semantics: it is no longer necessary to call one of

request(), seek() or deliver_xxx() in order to start the data flow.
Autonomous generators must be genuinely autonomous (having their own
process), or otherwise arrange to be called.  TCP does this by
starting the retry timer immediately.

Add some debugging statements.

src/net/tcp.c

@@ -210,7 +210,9 @@ static int tcp_open ( struct xfer_interface *xfer, struct sockaddr *peer,
 	DBGC ( tcp, "TCP %p allocated\n", tcp );
 	memset ( tcp, 0, sizeof ( *tcp ) );
 	xfer_init ( &tcp->xfer, &tcp_xfer_operations, &tcp->refcnt );
-	tcp->tcp_state = tcp->prev_tcp_state = TCP_CLOSED;
+	tcp->prev_tcp_state = TCP_CLOSED;
+	tcp->tcp_state = TCP_STATE_SENT ( TCP_SYN );
+	tcp_dump_state ( tcp );
 	tcp->snd_seq = random();
 	INIT_LIST_HEAD ( &tcp->queue );
 	tcp->timer.expired = tcp_expired;
@@ -221,6 +223,9 @@ static int tcp_open ( struct xfer_interface *xfer, struct sockaddr *peer,
 	if ( ( rc = tcp_bind ( tcp, bind_port ) ) != 0 )
 		goto err;
 
+	/* Start timer to initiate SYN */
+	start_timer ( &tcp->timer );
+
 	/* Attach parent interface, transfer reference to connection
 	 * list and return
 	 */
@@ -360,6 +365,10 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) {
 	size_t window;
 	int rc;
 
+	/* If retransmission timer is already running, do nothing */
+	if ( timer_running ( &tcp->timer ) )
+		return 0;
+
 	/* Calculate both the actual (payload) and sequence space
 	 * lengths that we wish to transmit.
 	 */
@@ -869,19 +878,6 @@ struct tcpip_protocol tcp_protocol __tcpip_protocol = {
  ***************************************************************************
  */
 
-/**
- * Ensure TCP connection has started
- *
- * @v tcp		TCP connection
- */
-static void tcp_ensure_started ( struct tcp_connection *tcp ) {
-	if ( ! ( tcp->tcp_state & TCP_STATE_SENT ( TCP_SYN ) ) ) {
-		tcp->tcp_state = TCP_SYN_SENT;
-		tcp_dump_state ( tcp );
-		tcp_xmit ( tcp, 0 );
-	}
-}
-
 /**
  * Close interface
  *
@@ -899,27 +895,6 @@ static void tcp_xfer_close ( struct xfer_interface *xfer, int rc ) {
 	tcp_xmit ( tcp, 0 );
 }
 
-/**
- * Request data
- *
- * @v xfer		Data transfer interface
- * @v offset		Offset to new position
- * @v whence		Basis for new position
- * @v len		Length of requested data
- * @ret rc		Return status code
- */
-static int tcp_xfer_request ( struct xfer_interface *xfer,
-			      off_t offset __unused, int whence __unused,
-			      size_t len __unused ) {
-	struct tcp_connection *tcp =
-		container_of ( xfer, struct tcp_connection, xfer );
-
-	/* Ensure connection has been started */
-	tcp_ensure_started ( tcp );
-
-	return 0;
-}
-
 /**
  * Seek to position
  *
@@ -933,9 +908,6 @@ static int tcp_xfer_seek ( struct xfer_interface *xfer, off_t offset,
 	struct tcp_connection *tcp =
 		container_of ( xfer, struct tcp_connection, xfer );
 
-	/* Ensure connection has been started */
-	tcp_ensure_started ( tcp );
-
 	/* TCP doesn't support seeking to arbitrary positions */
 	if ( ( whence != SEEK_CUR ) || ( offset != 0 ) )
 		return -EINVAL;
@@ -963,9 +935,6 @@ static int tcp_xfer_deliver_iob ( struct xfer_interface *xfer,
 	struct tcp_connection *tcp =
 		container_of ( xfer, struct tcp_connection, xfer );
 
-	/* Ensure connection has been started */
-	tcp_ensure_started ( tcp );
-
 	/* Enqueue packet */
 	list_add_tail ( &iobuf->list, &tcp->queue );
 
@@ -979,7 +948,7 @@ static int tcp_xfer_deliver_iob ( struct xfer_interface *xfer,
 static struct xfer_interface_operations tcp_xfer_operations = {
 	.close		= tcp_xfer_close,
 	.vredirect	= ignore_xfer_vredirect,
-	.request	= tcp_xfer_request,
+	.request	= ignore_xfer_request,
 	.seek		= tcp_xfer_seek,
 	.alloc_iob	= default_xfer_alloc_iob,
 	.deliver_iob	= tcp_xfer_deliver_iob,