Add iscsi_tcp_set_user_timeout function

This patch adds a user configurable option to set the TCP_USER_TIMEOUT
socket option. With this timeout set a broken TCP session is shutdown
after a given timeout even there are unacked packets. SO_KEEPALIVE
seems not to work in this case.

include/iscsi-private.h

@@ -84,6 +84,8 @@ struct iscsi_context {
 
 	int fd;
 	int is_connected;
+	
+	int tcp_user_timeout;
 
 	int current_phase;
 	int next_phase;

include/iscsi.h

@@ -967,6 +967,13 @@ iscsi_scsi_cancel_all_tasks(struct iscsi_context *iscsi);
 EXTERN void
 iscsi_set_debug(struct iscsi_context *iscsi, int level);
 
+/*
+ * This function is to set the TCP_USER_TIMEOUT option. It has to be called after iscsi
+ * context creation. The value given in ms is then applied each time a new socket is created.
+ */
+EXTERN void 
+iscsi_set_tcp_user_timeout(struct iscsi_context *iscsi, int timeout_ms);
+
 #ifdef __cplusplus
 }
 #endif