CP-51895: Drop FCoE support when fcoe_driver does not exists (#6202)

FCoE support will be removed from XS9 and dom0 will no longer provide
fcoe_driver. However, XS8 still actively support it.

Xapi checks the existence of fcoe_driver, and thinks all PIFs no longer
support FCoE if fcoe_driver not found

ocaml/networkd/lib/network_utils.ml

@@ -1067,12 +1067,19 @@ module Fcoe = struct
   let call ?log args = call_script ?log ~timeout:(Some 10.0) !fcoedriver args
 
   let get_capabilities name =
-    try
-      let output = call ~log:false ["--xapi"; name; "capable"] in
-      if Astring.String.is_infix ~affix:"True" output then ["fcoe"] else []
-    with _ ->
-      debug "Failed to get fcoe support status on device %s" name ;
-      []
+    match Sys.file_exists !fcoedriver with
+    | false ->
+        info "%s: %s not found, does not support FCoE" __FUNCTION__ !fcoedriver ;
+        [] (* Does not support FCoE *)
+    | true -> (
+      try
+        let output = call ~log:false ["--xapi"; name; "capable"] in
+        if Astring.String.is_infix ~affix:"True" output then ["fcoe"] else []
+      with _ ->
+        debug "%s: Failed to get fcoe support status on device %s" __FUNCTION__
+          name ;
+        []
+    )
 end
 
 module Sysctl = struct

ocaml/xapi/xapi_globs.ml

@@ -1689,11 +1689,6 @@ module Resources = struct
     ; ("xsh", xsh, "Path to xsh binary")
     ; ("static-vdis", static_vdis, "Path to static-vdis script")
     ; ("xen-cmdline-script", xen_cmdline_script, "Path to xen-cmdline script")
-    ; ( "fcoe-driver"
-      , fcoe_driver
-      , "Execute during PIF unplug to get the lun devices related with the \
-         ether interface of the PIF"
-      )
     ; ("list_domains", list_domains, "Path to the list_domains command")
     ; ("systemctl", systemctl, "Control the systemd system and service manager")
     ; ( "alert-certificate-check"
@@ -1797,6 +1792,12 @@ module Resources = struct
       , "Path to yum-config-manager command"
       )
     ; ("c_rehash", c_rehash, "Path to regenerate CA store")
+      (* Dropped since XS9, list here as XS8 still requires it *)
+    ; ( "fcoe-driver"
+      , fcoe_driver
+      , "Execute during PIF unplug to get the lun devices related with the \
+         ether interface of the PIF"
+      )
     ]
 
   let essential_files =

ocaml/xapi/xapi_pif.ml

@@ -319,33 +319,40 @@ let assert_no_other_local_pifs ~__context ~host ~network =
       )
 
 let assert_fcoe_not_in_use ~__context ~self =
-  let interface = Db.PIF.get_device ~__context ~self in
-  let output, _ =
-    Forkhelpers.execute_command_get_output !Xapi_globs.fcoe_driver
-      ["-t"; interface]
-  in
-  let output = String.trim output in
-  debug "Scsi ids on %s are: %s" interface output ;
-  let fcoe_scsids = Str.split (Str.regexp " ") output in
-  Helpers.get_my_pbds __context
-  |> List.iter (fun (_, pbd_rec) ->
-         let sr = pbd_rec.API.pBD_SR in
-         match Db.SR.get_type ~__context ~self:sr with
-         | "lvmofcoe" -> (
-           try
-             let scsid = List.assoc "SCSIid" pbd_rec.API.pBD_device_config in
-             if List.mem scsid fcoe_scsids then
-               raise
-                 (Api_errors.Server_error
-                    ( Api_errors.pif_has_fcoe_sr_in_use
-                    , [Ref.string_of self; Ref.string_of sr]
-                    )
-                 )
-           with Not_found -> ()
+  match Sys.file_exists !Xapi_globs.fcoe_driver with
+  | false ->
+      (* Does not support FCoE from XS9, presuming not in use
+       * Upgrade plugin will block upgrade with FCoE in use *)
+      debug "%s not found, does not support FCoE" !Xapi_globs.fcoe_driver
+  | true ->
+      let interface = Db.PIF.get_device ~__context ~self in
+      let output, _ =
+        Forkhelpers.execute_command_get_output !Xapi_globs.fcoe_driver
+          ["-t"; interface]
+      in
+      let output = String.trim output in
+      debug "%s: SCSI ids on %s are: %s" __FUNCTION__ interface output ;
+      let fcoe_scsids = Str.split (Str.regexp " ") output in
+      Helpers.get_my_pbds __context
+      |> List.iter (fun (_, pbd_rec) ->
+             let sr = pbd_rec.API.pBD_SR in
+             match Db.SR.get_type ~__context ~self:sr with
+             | "lvmofcoe" -> (
+               match List.assoc_opt "SCSIid" pbd_rec.API.pBD_device_config with
+               | Some scsid ->
+                   if List.mem scsid fcoe_scsids then
+                     raise
+                       (Api_errors.Server_error
+                          ( Api_errors.pif_has_fcoe_sr_in_use
+                          , [Ref.string_of self; Ref.string_of sr]
+                          )
+                       )
+               | None ->
+                   ()
+             )
+             | _ ->
+                 ()
          )
-         | _ ->
-             ()
-     )
 
 let find_or_create_network (bridge : string) (device : string) ~managed
     ~__context =