inetd(8): Provide HTTP proxy example using netcat

One of the fortunes that are included in freebsd-tips talks about how
the superserver can be used to proxy connections with netcat, but there are
no examples provided. This commit adds an example with comment explaining
what it does.

Submitted by:	debdrup
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D24800

usr.sbin/inetd/inetd.8

@@ -28,7 +28,7 @@
 .\"     from: @(#)inetd.8	8.3 (Berkeley) 4/13/94
 .\" $FreeBSD$
 .\"
-.Dd January 12, 2008
+.Dd May 12, 2020
 .Dt INETD 8
 .Os
 .Sh NAME
@@ -800,6 +800,8 @@ shell        stream  tcp46  nowait root  /usr/libexec/rshd rshd
 tcpmux/+date stream  tcp   nowait guest /bin/date                date
 tcpmux/phonebook stream tcp nowait guest /usr/local/bin/phonebook phonebook
 rstatd/1-3   dgram   rpc/udp wait root  /usr/libexec/rpc.rstatd  rpc.rstatd
+# Use netcat as a one-shot HTTP proxy with nc (from freebsd-tips fortune)
+http         stream  tcp   nowait nobody /usr/bin/nc nc -N dest-ip 80
 /var/run/echo stream unix  nowait root	internal
 #@ ipsec ah/require
 chargen      stream  tcp   nowait root  internal
@@ -914,6 +916,7 @@ in the
 database.
 .El
 .Sh SEE ALSO
+.Xr nc 1 ,
 .Xr ipsec_set_policy 3 ,
 .Xr hosts_access 5 ,
 .Xr hosts_options 5 ,