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, 48 insertions, 0 deletions

diff --git a/etc/iscsid.conf b/etc/iscsid.conf
index e8f83fb..78c225c 100644
--- a/etc/iscsid.conf
+++ b/etc/iscsid.conf
@@ -22,6 +22,12 @@
 # Default for upstream open-iscsi scripts (uncomment to activate).
 iscsid.startup = /sbin/iscsid
 
+
+
+
+##############################
+# SendTargets Discovery Daemon
+##############################
 # If instead of doing discovery with iscsiadm and then logging
 # into the targets stored in the node db, set the following value
 # to have iscsid perform SendTargets discovery and log into all
@@ -35,6 +41,7 @@ iscsid.startup = /sbin/iscsid
 # default 3260 will be used.
 #
 # Example (first address has a port and the final two use the default 3260):
+#
 # discovery.daemon.sendtargets.addresses = 192.168.0.21,1234 192.168.1.20 192.168.10.10
 #
 # By default iscsid will check the discovery addresses above every 30
@@ -49,6 +56,47 @@ iscsid.startup = /sbin/iscsid
 # To remove them run "iscsiadm -m session -r $SID -u"
 
 
+
+#######################
+# iSNS Discovery Daemon
+#######################
+
+
+# iSNS can also be used by setting:
+#
+# discovery.daemon.isns.addresses = 192.168.0.21,1234 192.168.1.20 192.168.10.10
+#
+# The default port is 3205.
+#
+# By default iscsid will perform iSNS discovery to the addresses, register
+# for State Change Notifications (SCNs) and then login/logout of portals
+# depending on the SCN.
+#
+# To change the default behavior the following setting can be used:
+#
+# discovery.daemon.isns.poll_interval = 30
+#
+# - If set to 0, it will perform discovery once then exit.
+# - If set to greater than 0 then it will perform discovery every X seconds.
+#   It will still attempt to register for SCNs, but will still poll with
+#   a DevAttrQuery for all targets.
+#
+#
+#   ALERT
+#   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+#   This is needed for servers like Microsofts where they allow SCN
+#   registrations, but do not send SCN events. To auto discover new targets
+#   we have to poll. It is also useful for servers like linux-isns where it
+#   sometimes does not send SCN events in the proper format, so they
+#   may not get handled.
+#   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+#
+# - If set to less than zero (or not set at all) it will perform the default
+#   behavior.
+#
+# Note: like with SendTargets, logout of portals is not yet supported.
+
+
 #############################
 # NIC/HBA and driver settings
 #############################