iscsi-target: Initial traditional TCP conversion to iscsit_transport

This patch performs the initial conversion of existing traditional iscsi
to use iscsit_transport API callers.  This includes:

- iscsi-np cleanups for iscsit_transport_type
- Add iscsi-np transport calls w/ ->iscsit_setup_up() and ->iscsit_free_np()
- Convert login thread process context to use ->iscsit_accept_np() for
  connections with pre-allocated struct iscsi_conn
- Convert existing socket accept code to iscsit_accept_np()
- Convert login RX/TX callers to use ->iscsit_get_login_rx() and
  ->iscsit_put_login_tx() to exchange request/response PDUs
- Convert existing socket login RX/TX calls into iscsit_get_login_rx()
  and iscsit_put_login_tx()
- Change iscsit_close_connection() to invoke ->iscsit_free_conn() +
  iscsit_put_transport() calls.
- Add iscsit_register_transport() + iscsit_unregister_transport() calls
  to module init/exit

v4 changes:

- Add missing iscsit_put_transport() call in iscsi_target_setup_login_socket()
  failure case

v2 changes:

- Update module init/exit to use register_transport() + unregister_transport()

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/iscsi/iscsi_target_parameters.c b/drivers/target/iscsi/iscsi_target_parameters.c
index ca2be40..84ce94a 100644
--- a/drivers/target/iscsi/iscsi_target_parameters.c
+++ b/drivers/target/iscsi/iscsi_target_parameters.c
@@ -59,7 +59,7 @@
 	char *text_buf,
 	int text_length)
 {
-	int length, tx_sent;
+	int length, tx_sent, iov_cnt = 1;
 	struct kvec iov[2];
 
 	length = (ISCSI_HDR_LEN + text_length);
@@ -67,8 +67,12 @@
 	memset(&iov[0], 0, 2 * sizeof(struct kvec));
 	iov[0].iov_len		= ISCSI_HDR_LEN;
 	iov[0].iov_base		= pdu_buf;
-	iov[1].iov_len		= text_length;
-	iov[1].iov_base		= text_buf;
+
+	if (text_buf && text_length) {
+		iov[1].iov_len	= text_length;
+		iov[1].iov_base	= text_buf;
+		iov_cnt++;
+	}
 
 	/*
 	 * Initial Marker-less Interval.
@@ -77,7 +81,7 @@
 	 */
 	conn->if_marker += length;
 
-	tx_sent = tx_data(conn, &iov[0], 2, length);
+	tx_sent = tx_data(conn, &iov[0], iov_cnt, length);
 	if (tx_sent != length) {
 		pr_err("tx_data returned %d, expecting %d.\n",
 				tx_sent, length);