tcp: account sent/received IP ECN markings independently

[rscheff]

Summary

TCPS (netstat -s) would not differentiate between received and sent
ECN-marked packets, but would only account received packets if the
tcp session had negotiated ECN support.

It is known that some devices incorrectly set the historic TOS byte
and may infringe on the IP ECN bits - but without accounting IP ECN
packets where the session is not ECN-enabled would mask such misconfigurations.

[rscheff]

sys/netinet/tcp_var.h

828

not sure if we will need a sent ce counter - this may only be relevant for future CC where a receiver driving marking is also possible. Or for path probing...

[rscheff]

• remove tcps_ecn_sndce

[tuexen]

sys/netinet/tcp_ecn.c

124

Why are you removing this line?

sys/netinet/tcp_var.h

831

I think you want to go from 6 to 4 now, not to 3.

However, wasn't the plan to not change this at all in the main branch?

usr.bin/netstat/inet.c

831

Don't you need to change the "\t{:*/%ju} " stuff?

[rscheff]

• fix oversights

[rscheff]

• comment typo