CA-411122: do not call set-iscsi-initiator with an empty string for IQN

Back in 2018 a4a94b3 rejected empty IQNs in set_iscsi_iqn API calls.
However hosts are created with an empty IQN, and if this code runs too early then it will attempt to call `set-iscsi-initiator` with an empty string for the IQN:
```
/opt/xensource/libexec/set-iscsi-initiator  myhost
```

About a second later the script is called again with the correct value.
This could potentially result in the iscsid service being restarted multiple times (and if a restart is still pending when restart is called a 2nd time I'm not sure it'll take effect, so we might be left with an empty initiator).

It is best to avoid setting empty initiators. The exception would be raised and ignore due to the log_and_ignore in the caller.

Also log wherever the IQN is set using %S, so that we notice if it ends up containing some extra whitespace characters.

Signed-off-by: Edwin Török <[email protected]>

Author: edwintorok

ocaml/xapi/xapi_host.ml

@@ -2790,6 +2790,7 @@ let set_uefi_certificates ~__context ~host:_ ~value:_ =
 let set_iscsi_iqn ~__context ~host ~value =
   if value = "" then
     raise Api_errors.(Server_error (invalid_value, ["value"; value])) ;
+  D.debug "%s: iqn=%S" __FUNCTION__ value ;
   (* Note, the following sequence is carefully written - see the
      other-config watcher thread in xapi_host_helpers.ml *)
   Db.Host.remove_from_other_config ~__context ~self:host ~key:"iscsi_iqn" ;

ocaml/xapi/xapi_host_helpers.ml

@@ -497,10 +497,13 @@ module Configuration = struct
     [iqn; hostname_chopped]
 
   let set_initiator_name iqn =
+    if iqn = "" then
+      raise Api_errors.(Server_error (invalid_value, ["iqn"; iqn])) ;
     let hostname = Unix.gethostname () in
     (* CA-377454 - robustness, create dir if necessary *)
     Unixext.mkdir_rec "/var/lock/sm/iscsiadm" 0o700 ;
     let args = make_set_initiator_args iqn hostname in
+    D.debug "%s: iqn=%S" __FUNCTION__ iqn ;
     ignore (Helpers.call_script !Xapi_globs.set_iSCSI_initiator_script args)
 
   let set_multipathing enabled =
@@ -541,6 +544,7 @@ module Configuration = struct
             | Some "" ->
                 ()
             | Some iqn when iqn <> host_rec.API.host_iscsi_iqn ->
+                D.debug "%s: iqn=%S" __FUNCTION__ iqn ;
                 Client.Client.Host.set_iscsi_iqn ~rpc ~session_id ~host:host_ref
                   ~value:iqn
             | _ ->