Add IPv6 support for address parsing and unparsing in ng_ksocket.

[p.mousavizadeh_protonmail.com]

Summary

Add IPv6 support for address parsing and unparsing in ng_ksocket.

• Fix issues related to D23788.
• Validate square brackets as a requirement. (src, man)

Co-authored by: Neel Chauhan <neel AT neelc DOT org>

Note: Phabricator won't let me use the update diff function from the original revision.

Test Plan

Here is my current netflow export configuration and it works:

kldstat -qm ng_netflow || kldload ng_netflow
kldstat -qm ng_ether || kldload ng_ether
kldload ./ng_ksocket.ko
ngctl mkpeer vtnet0: netflow lower iface0
ngctl name vtnet0:lower netflow          
ngctl connect vtnet0: netflow: upper out0
ngctl mkpeer netflow: ksocket export9 inet6/dgram/udp6
ngctl name netflow:export9 ngk
ngctl msg ngk: connect inet6/[fdb5:c59b:114e:8db4::1]:4444

I have tested this for tcp6 protocol, msg bind, and link-local with [fe80::1%vtnet0]:4444.

[glebius]

sys/netgraph/ng_ksocket.c

62

What does require if_var.h?

[glebius]

Also, any meaningful change to a manual page requires bumping the .Dd value at the beginning of the page to today's date.

[p.mousavizadeh_protonmail.com]

Bump .Dd in ng_ksocket.4
update value from January 9, 2012 to January 9, 2025

[p.mousavizadeh_protonmail.com]

@glebius: Also, Here is my github repo as you requested.
spmzt/freebsd-src/tree/ksocket_ipv6: D48204

sys/netgraph/ng_ksocket.c

62

I am using ifunit() at line 352, and its function declared in <net/if_var.h>. Maybe I think it's required due to my lack of knowledge, Should I remove it?

[glebius]

sys/netgraph/ng_ksocket.c

62

Sorry, I though it belongs to net/if.h