Make RTO.Initial for TCP controllable via sysctl

[tuexen]

Summary

Add sysctl variable net.inet.tcp.rexmit_initial for setting RTO.Initial used by TCP.

[koobs]

Thank you for this @tuexen!

sys/netinet/tcp_timer.c

116 ↗

(On Diff #54376)

I don't know if we have consistent standards/guidelines for sysctl descriptions (would be nice) for 'units' 'minimum' and 'maximum' values, but, possible improvements:

• + in seconds or Units: seconds.
• + Minimum: 1 (based on forced min value in code above)

So, something like:

"Initial Retransmission Timeout in seconds. Minimum: 1"

[tuexen]

The unit would be milli seconds, not seconds for the sysctl-variable. In general, I agree that it would be good to give at least the unit for sysctl variables, but

sys/netinet/tcp_timer.c

116 ↗

(On Diff #54376)

All timer related sysctl variables for TCP are in ms. The documentation string I added is based on consistency with the existing ones.

I agree, that giving the unit (ms) might help some users, but I think this should be added as a separate commit. I'm happy to do that once this change is in tree.

[koobs]

Thank you for the insight @tuexen

[0mp]

OK from manpages