tcp_bblog.4: Add a manual page for TCP Blackbox Logging

[gbe]

Summary

Add a manual page for the TCP Blackbox Logging.

The tcp_bblog facility provides structured logging of TCP stack activity
for debugging and performance analysis. It is implemented in the kernel
and allows per-connection tracing of TCP events with low overhead.

MFC after: 1 week

Test Plan

mandoc -Tlint checks

[tuexen]

share/man/man4/tcp_bblog.4

14

I don't see this anywhere in the tree. Remove this line?

48

... or tcpsso. You might want to mention it.

85

This directory is not specific to black box logging, but the userland tool tcplog_dumper. Not sure if it should be mentioned here.

92

Maybe: Enable continual logging for all TCP connections:

96

You might want to add a note that using a config with

net.inet.tcp.bb.log_auto_mode=1

keeps up to the last net.inet.tcp.bb.log_session_limit entries stored at the TCP endpoint. Nothing is dumped to disk.
So when debugging TCP related panics, this is a good way to capture information about the panic.

107

You also might want to cross reference to tcpsso.8. The man page shows an example how to enable continual logging for a specific TCP connection via the command line.

121

It was written by Jonathan Looney (jtl) and Randall Stewart (rrs), not by me.

[tuexen]

Thanks for the effort of writing an initial man page. I wanted to do this for a long time...

[tuexen]

share/man/man4/tcp_bblog.4

107

You might also add a reference to Adventures in TCP/IP: TCP Black Box Logging.

[ziaee]

Couple of minor nits, thank you so much for doing this! Also, don't forget to add this manual to the Makefile!

share/man/man4/tcp_bblog.4

1–5

we still use this blank comment for consistency with C, but we don't use the hyphen anymore. style.9 and the licensing guide suggest putting the copyright at the top in spdx only format.

13

these don't need to be quoted, and thank you so much for using mdoc conformant style.

50–51

71–72