How to set ECN in IP header to zero by setting flow_stats = STLFlowLatencyStats(pg_id=X) in the STLStream() argument

[s5uishida]

Hi community,

If use STLStream() with the argument flow_stats = STLFlowLatencyStats(pg_id=X), even if specify IP(tos=0) in the packet argument of STLStream() as shown below, when capture the generated packet, ECN (6-7th bits of tos(8 bits)) is 0x01.

packet = STLPktBuilder(pkt = Ether()/IP(...,tos=0)/...)

How can I set ECN of the IP header of the generated packet to 0x00?

Thanks in advance.