Re-add Veeam Listing workaround (#16593)

cmd/erasure-server-pool.go

@@ -1207,6 +1207,7 @@ func (z *erasureServerPools) ListObjectVersions(ctx context.Context, bucket, pre
 	if marker == "" && versionMarker != "" {
 		return loi, NotImplemented{}
 	}
+
 	opts := listPathOptions{
 		Bucket:      bucket,
 		Prefix:      prefix,
@@ -1217,6 +1218,17 @@ func (z *erasureServerPools) ListObjectVersions(ctx context.Context, bucket, pre
 		AskDisks:    globalAPIConfig.getListQuorum(),
 		Versioned:   true,
 	}
+
+	// Shortcut for APN/1.0 Veeam/1.0 Backup/10.0
+	// It requests unique blocks with a specific prefix.
+	// We skip scanning the parent directory for
+	// more objects matching the prefix.
+	ri := logger.GetReqInfo(ctx)
+	if ri != nil && strings.Contains(ri.UserAgent, `1.0 Veeam/1.0 Backup`) && strings.HasSuffix(prefix, ".blk") {
+		opts.BaseDir = prefix
+		opts.Transient = true
+	}
+
 	// set bucket metadata in opts
 	opts.setBucketMeta(ctx)