sockstat: split FreeBSD, NetBSD and Linux implementations (#12040)

* sockstat: split FreeBSD, NetBSD and Linux implementations

---------

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>
Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: cyqsimon <28627918+cyqsimon@users.noreply.github.com>

pages/netbsd/sockstat.md

@@ -0,0 +1,26 @@
+# sockstat
+
+> List open Internet or UNIX domain sockets.
+> Note: this program is a rewrite for NetBSD 3.0 from FreeBSD's `sockstat`.
+> See also: `netstat`.
+> More information: <https://man.freebsd.org/cgi/man.cgi?sockstat>.
+
+- Show information for IPv4, IPv6 and Unix sockets for both listening and connected sockets:
+
+`sockstat`
+
+- Show information for IPv[4]/IPv[6] sockets [l]istening on specific [p]orts using a specific [P]rotocol:
+
+`sockstat -{{4|6}} -l -P {{tcp|udp|sctp|divert}} -p {{port1,port2...}}`
+
+- Also show [c]onnected sockets, showing [u]nix sockets:
+
+`sockstat -cu`
+
+- Only show [n]umeric output, without resolving symbolic names for addresses and ports:
+
+`sockstat -n`
+
+- Only list sockets of the specified address [f]amily:
+
+`sockstat -f {{inet|inet6|local|unix}}`