iscsi: Add Serial Number Arithmetic LT and GT into iscsi_proto.h

This patch moves the iscsi_sna_lt() and iscsi_sna_lte(), along with
iscsi_sna_gt() and iscsi_sna_gte() from iscsi_target_mod into
static inlines inside of include/scsi/iscsi_proto.h

This patch also includes the ISCSI_HDR_LEN and ISCSI_CRC_LEN
definitions.

(Added JesperJ simpliciation for iscsi_sna_* usage)
Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>

drivers/scsi/libiscsi.c

@@ -84,22 +84,6 @@ MODULE_PARM_DESC(debug_libiscsi_eh,
 					     __func__, ##arg);		\
 	} while (0);
 
-/* Serial Number Arithmetic, 32 bits, less than, RFC1982 */
-#define SNA32_CHECK 2147483648UL
-
-static int iscsi_sna_lt(u32 n1, u32 n2)
-{
-	return n1 != n2 && ((n1 < n2 && (n2 - n1 < SNA32_CHECK)) ||
-			    (n1 > n2 && (n2 - n1 < SNA32_CHECK)));
-}
-
-/* Serial Number Arithmetic, 32 bits, less than, RFC1982 */
-static int iscsi_sna_lte(u32 n1, u32 n2)
-{
-	return n1 == n2 || ((n1 < n2 && (n2 - n1 < SNA32_CHECK)) ||
-			    (n1 > n2 && (n2 - n1 < SNA32_CHECK)));
-}
-
 inline void iscsi_conn_queue_work(struct iscsi_conn *conn)
 {
 	struct Scsi_Host *shost = conn->session->host;

include/scsi/iscsi_proto.h

@@ -29,9 +29,39 @@
 /* default iSCSI listen port for incoming connections */
 #define ISCSI_LISTEN_PORT	3260
 
+/* iSCSI header length */
+#define ISCSI_HDR_LEN		48
+
+/* iSCSI CRC32C length */
+#define ISCSI_CRC_LEN		4
+
 /* Padding word length */
 #define ISCSI_PAD_LEN		4
 
+/*
+ * Serial Number Arithmetic, 32 bits, RFC1982
+ */
+
+static inline int iscsi_sna_lt(u32 n1, u32 n2)
+{
+	return (s32)(n1 - n2) < 0;
+}
+
+static inline int iscsi_sna_lte(u32 n1, u32 n2)
+{
+	return (s32)(n1 - n2) <= 0;
+}
+
+static inline int iscsi_sna_gt(u32 n1, u32 n2)
+{
+	return (s32)(n1 - n2) > 0;
+}
+
+static inline int iscsi_sna_gte(u32 n1, u32 n2)
+{
+	return (s32)(n1 - n2) >= 0;
+}
+
 /*
  * useful common(control and data pathes) macro
  */