iscsid: add isns discovery daemon and SCN support

This adds the following params to iscsid.conf
discovery.daemon.isns.addresses
discovery.daemon.isns.poll_interval

These work like SendTargets where if you the param iscsid will do
discovery and log into the portals found.

This also adds iSNS SCN support. Like the other code it only supports
login of new targets.

Some notes:
- It does not appear to work with the Microsoft iSNS server
shipping with Windows 2008 rc. I have not tested 2003.
The server does not seem to be sending any SCNs and at the
same time when we register for SCNs it tells us the operation
was successful. From the Microsoft docs it appears that
the server does not support SCN events.

- Linux-isns is not working with our code. The Linux-isns
code appears to be sending iSNS SCN pdus with an incorrect
format.

- It is working with open-isns.git.

1 files changed, 29 insertions, 3 deletions

diff --git a/README b/README
index b6fd1eb..3ff6726 100644
--- a/README
+++ b/README
@@ -799,9 +799,13 @@ There are three steps needed to set up a system to use iSCSI storage:
 7.3. Automate target logins for future system reboots.
 
 The init scripts will start the iSCSI daemon and log into any
-connections or nodes that are set up for automatic login. If your distro
-does not have a init script, then you will have to start the daemon
-and log into the targets manually.
+portals that are set up for automatic login (discussed in 7.2)
+or discovered through the discover daemon iscsid.conf params
+(discussed in 7.1.2).
+
+If your distro does not have a init script, then you will have to start the
+daemon and log into the targets manually.
+
 
 7.1.1 iSCSI startup using the init script
 -----------------------------------------------
@@ -832,6 +836,28 @@ gets installed with "make install"
 
 will usually get you started.
 
+
+7.1.2 Automatic Discovery and Login
+-----------------------------------
+
+When iscsid starts it will check iscsid.conf for:
+
+discovery.daemon.sendtargets.addresses =
+discovery.daemon.sendtargets.poll_interval =
+
+discovery.daemon.isns.addresses =
+discovery.daemon.isns.poll_interval =
+
+being set. If an address or addresses are set, iscsid will perform discovery
+to the address every poll_interval seconds, and it will log into any portals
+found from the discovery source using the ifaces in /etc/iscsi/ifaces.
+
+Note: iscsid will login into new portals, but does not yet support logging
+out of portals that are no longer returned during discovery.
+
+See the iscsid.conf for more examples.
+
+
 7.1.2 Manual Startup:
 ---------------------