xapi_vif: Guarantee the device parameter is an unsigned decimal integer (#6495)

This has been always true as xapi will call valid_device on VIF creation
to
make sure device is an integer, but the datamodel type of 'device' is
string,
    without any such guarantees.

Specify the guarantee in the documentation and make the check stricter
(int_of_string will accept "0x9fe" as an integer, for example), making
sure
that the device is specifically a decimal unsigned integer.
allowed_VIF_devices
has already enforced the unsigned decimal integer limitation on
compliant clients.

This could be helpful in ensuring that the clients will always be right
in
sorting devices as numbers, not as strings (so that "2" follows "1"
instead of
    the string order of "1"->"10"->"11", etc.).

Author: last-genius

ocaml/idl/datamodel.ml

@@ -3866,7 +3866,9 @@ module VIF = struct
                   , "order in which VIF backends are created by xapi"
                   )
                 ]
-              "device" "order in which VIF backends are created by xapi"
+              "device"
+              "order in which VIF backends are created by xapi. Guaranteed to \
+               be an unsigned decimal integer."
           ; field ~qualifier:StaticRO ~ty:(Ref _network)
               ~lifecycle:
                 [

ocaml/idl/schematest.ml

@@ -3,7 +3,7 @@ let hash x = Digest.string x |> Digest.to_hex
 (* BEWARE: if this changes, check that schema has been bumped accordingly in
    ocaml/idl/datamodel_common.ml, usually schema_minor_vsn *)
 
-let last_known_schema_hash = "dc1ccf295f957509f7eac4a005d17965"
+let last_known_schema_hash = "4cd835e2557dd7b5cbda6c681730c447"
 
 let current_schema_hash : string =
   let open Datamodel_types in

ocaml/xapi/xapi_vif_helpers.ml

@@ -192,10 +192,11 @@ let clear_current_operations ~__context ~self =
 
 (**************************************************************************************)
 
-(** Check if the device string has the right form *)
+(** Check if the device string has the right form - it should only be an
+    unsigned decimal integer *)
 let valid_device dev =
   try
-    ignore (int_of_string dev) ;
+    Scanf.sscanf dev "%u%!" ignore ;
     true
   with _ -> false