pyloxi: fix OXM lengths
The length field only includes the payload, not the header.
diff --git a/py_gen/codegen.py b/py_gen/codegen.py
index f55610b..90ddf23 100644
--- a/py_gen/codegen.py
+++ b/py_gen/codegen.py
@@ -84,7 +84,7 @@
oxm_class = 0x8000
oxm_type = util.primary_wire_type(cls, version)
oxm_masked = cls.find('masked') != -1 and 1 or 0
- oxm_len = of_g.base_length[(cls, version)]
+ oxm_len = of_g.base_length[(cls, version)] - 4
type_values['type_len'] = '%#x' % (oxm_class << 16 | oxm_type << 8 | \
oxm_masked << 8 | oxm_len)
elif cls == "of_match_v3":