if there's a http error, return the error

mirage/unikernel.ml

@@ -309,12 +309,15 @@ module Make
       (* XXX: we may be in trouble if different hash functions are used for the same archive *)
       let ( >>>= ) = Lwt_result.bind in
       fun response r data ->
-        Lwt.return r >>>= fun (digests, swap) ->
-        let digests = Archive_checksum.update_digests digests data in
-        active_add_bytes url (String.length data);
-        Swap.append swap data >|= function
-        | Ok () -> Ok (digests, swap)
-        | Error swap_err -> Error (`Swap swap_err)
+        if Http_mirage_client.Status.is_successful response.Http_mirage_client.status then
+          Lwt.return r >>>= fun (digests, swap) ->
+          let digests = Archive_checksum.update_digests digests data in
+          active_add_bytes url (String.length data);
+          Swap.append swap data >|= function
+          | Ok () -> Ok (digests, swap)
+          | Error swap_err -> Error (`Swap swap_err)
+        else
+          Lwt.return (Error `Bad_response)
 
     let check_csums_digests csums digests =
       let csums' = Archive_checksum.digests_to_hm digests in
@@ -664,7 +667,7 @@ stamp: %S
           (SM.cardinal disk.Disk.md5s)
           (KV.free disk.Disk.dev)
       in
-      let sort_by_ts a b = Ptime.compare a b in
+      let sort_by_ts a b = Ptime.compare b a in
       let active_downloads =
         let header = "<h2>Active downloads</h2><ul>" in
         let content =