examples/jails: Allow any character in interface names

[jlduran]

Summary

Interface names have no limitations on the allowed character set, only
a length restriction.

Widen the allowed character set for interface names to include any
printable character.

PR: 290916

[jlduran]

Include the same pattern in jib_destroy(), jng_shutdown(), and jng_stats().

[crest_freebsd_rlwinm.de]

Using tabs, spaces or newlines in interface names is just asking for trouble. A lot of the rc.d shell code is not properly written to deal with such intentional stupidity.

[jlduran]

In D53865#1230620, @crest_freebsd_rlwinm.de wrote:

Using tabs, spaces or newlines in interface names is just asking for trouble. A lot of the rc.d shell code is not properly written to deal with such intentional stupidity.

Right, I agree, I believe isprint(3) does not include those...
Probably the original pattern stems from rc.subr (*[!a-zA-Z0-9_]). If I remember correctly, @dteske preferred creating jails using rc.conf and not jail.conf (a vague recollection of some YouTube video).

[tschetter.victor_gmail.com]

Interesting.

BastilleBSD has code to automatically sed ‘s/-/_/‘ for the /etc/rc.conf part when jail names contain a hyphen.

I would at least consider allowing (.) as they are very common when using vlan with interfaces.

[dteske]

This is an excellent change. Moving forward with landing it. Thank you for your hard work (sorry for the delay).