Update the ipfw section in the Handbook: kernel options, ipfw0, configuration

[f.toscan_hotmail.it]

Summary

First attempt to update the ipfw section in the Handbook. I've documented some kernel compile options, introduced ipfw0 and sysrc usage.
If the direction is right I can go further with logging and in-kernel nat.
I've created this revision as instructed (see Bug 232956)

Test Plan

The patch attached was tested on 4.11.2018 and the documentation build was fine.

[debdrup]

Looks Good To Me!

[bcr]

Can you run textproc/igor on your change and fix the errors that are reported? The indentation of the following line seems way off:
<para>To enable logging through a dedicated interface named ...

[allanjude]

As a general comment, since IPFW can be loaded as a kernel module now, I'd make that the recommended configuration at the start of the file, and include the 'how to compile a kernel with ipfw in it' at the bottom of the chapter, so as not to send new users off into more complicated configurations for no reason.

[f.toscan_hotmail.it]

Thank you for your feedback.

@bcr : sure, I'll fix that.

@allanjude : I thought to make the proposed patch the least intrusive as possible; if you think that moving the kernel plumbing part to the bottom of the chapter is better, I'll be happy to try to shuffle things once I got this minor fix right.

Thank you all, I'll be back in some days

[f.toscan_hotmail.it]

Here is a new diff. I fixed style bugs found running igor, as suggested by Benedict Reuschling; then I moved the kernel compile options part to the end of the chapter, as requested by Allan Jude.

Thanks for review, I'm waiting for your comments.

[bcr]

Sorry for the wait. Looks good to me. I can get it committed.

[f.toscan_hotmail.it]

Ok thank you.
I have a draft for the logging section: I'll open a new bug report after this is committed.

[debdrup]

Out of interest, who's taking care of the commit?

[crees]

Unlees @bcr commits it first or objects, I'll do it.

[bcr]

Go ahead...

[ygy]

Thanks @bcr and @crees, closing https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=232956 now.