remote needle read add checksum

go/weed/weed_server/volume_server_handlers_read.go

@@ -333,6 +333,12 @@ func (vs *VolumeServer) readRemoteNeedle(vid string, n *storage.Needle, collecti
 			n.Flags = byte(i)
 		}
 	}
+	if h := resp.Header.Get("Seaweed-Checksum"); h != "" {
+		if i, err := strconv.ParseInt(h, 16, 64); err == nil {
+			n.Checksum = storage.CRC(i)
+		}
+	}
+
 	if h := resp.Header.Get("Seaweed-LastModified"); h != "" {
 		if i, err := strconv.ParseUint(h, 16, 64); err == nil {
 			n.LastModified = i

go/weed/weed_server/volume_server_handlers_sync.go

@@ -176,6 +176,7 @@ func (vs *VolumeServer) getNeedleHandler(w http.ResponseWriter, r *http.Request)
 		return
 	}
 	w.Header().Set("Seaweed-Flags", strconv.FormatInt(int64(n.Flags), 16))
+	w.Header().Set("Seaweed-Checksum", strconv.FormatInt(int64(n.Checksum), 16))
 	if n.HasLastModifiedDate() {
 		w.Header().Set("Seaweed-LastModified", strconv.FormatUint(n.LastModified, 16))
 	}