On solo5 manifest mismatch print the manifest (#196)

* On solo5 manifest mismatch print the manifest

This makes it easier for users of the client to figure out what devices
are expected without them having to know to query the solo5 manifest
using solo5-elftool themselves.

* Print devices only instead of the whole manifest

* Code review: Tweak error message

Co-authored-by: Hannes Mehnert <hannes@mehnert.org>

---------

Co-authored-by: Hannes Mehnert <hannes@mehnert.org>

src/vmm_unix.ml

@@ -252,34 +252,40 @@ let check_solo5_tender target version =
     Error (`Msg (Fmt.str "unexpected solo5 tender --version output, expected one line with 'ABI version %u', got %s"
                    version (String.concat "\n" out)))
 
-let solo5_image_devices image =
-  let* mft = Solo5_elftool.query_manifest (owee_buf_of_str image) in
-  Ok (List.fold_left
-        (fun (block_devices, networks) -> function
-           | Solo5_elftool.Dev_block_basic name -> name :: block_devices, networks
-           | Solo5_elftool.Dev_net_basic name -> block_devices, name :: networks)
-        ([], []) mft.entries)
+let solo5_image_devices mft =
+  List.fold_left
+    (fun (block_devices, networks) -> function
+       | Solo5_elftool.Dev_block_basic name -> name :: block_devices, networks
+       | Solo5_elftool.Dev_net_basic name -> block_devices, name :: networks)
+    ([], []) mft.Solo5_elftool.entries
 
 let equal_string_lists b1 b2 err =
   if String_set.(equal (of_list b1) (of_list b2)) then
     Ok ()
   else
     Error (`Msg err)
 
-let devices_match ~bridges ~block_devices (manifest_block, manifest_net) =
+let devices_match ~bridges ~block_devices mft =
+  let (manifest_block, manifest_net) = solo5_image_devices mft in
+  let pp_entry ppf = function
+    | Solo5_elftool.Dev_block_basic name -> Fmt.pf ppf "block %S" name
+    | Solo5_elftool.Dev_net_basic name -> Fmt.pf ppf "net %S" name
+  in
   let* () =
     equal_string_lists manifest_block block_devices
-      "specified block device(s) does not match with manifest"
+      (Fmt.str "specified block device(s) does not match with manifest. Devices present in manifest: %a"
+         Fmt.(list ~sep:(any ", ") pp_entry) mft.entries)
   in
   equal_string_lists manifest_net bridges
-    "specified bridge(s) does not match with the manifest"
+    (Fmt.str "specified bridge(s) does not match with the manifest. Devices present in manifest: %a"
+         Fmt.(list ~sep:(any ", ") pp_entry) mft.entries)
 
 let manifest_devices_match ~bridges ~block_devices image =
-  let* things = solo5_image_devices image in
+  let* mft = Solo5_elftool.query_manifest (owee_buf_of_str image) in
   let bridges = List.map (fun (b, _, _) -> b) bridges
   and block_devices = List.map (fun (b, _, _) -> b) block_devices
   in
-  devices_match ~bridges ~block_devices things
+  devices_match ~bridges ~block_devices mft
 
 let bridge_name (service, b, _mac) = match b with None -> service | Some b -> b