wireshark: fix buf in OFReader
diff --git a/wireshark_gen/templates/_ofreader.lua b/wireshark_gen/templates/_ofreader.lua
index b95c9f6..2ec160d 100644
--- a/wireshark_gen/templates/_ofreader.lua
+++ b/wireshark_gen/templates/_ofreader.lua
@@ -37,8 +37,8 @@
     end
 
     self.read_all = function()
-        local r = buf(offset, buf.len() - offset)
-        offset = buf.len()
+        local r = buf(offset, buf:len() - offset)
+        offset = buf:len()
         return r
     end