BSD: sysctl net.inet.ip.forwarding=1 is not necessary.

If your machine is a firewall/router, it affects whether people behind the
router can use your sshuttle connection - in the same way that it affects
whether they can route *anything* through you.  And thus, it should be set
by the admin, not by sshuttle.

sshuttle works fine for the local user either way.

(This also affects MacOS since it's a BSD variant.)

firewall.py

@@ -129,7 +129,6 @@ def do_ipfw(port, subnets):
 
     if subnets:
         sysctl_set('net.inet.ip.fw.enable', 1)
-        sysctl_set('net.inet.ip.forwarding', 1)
         sysctl_set('net.inet.ip.scopedroute', 0)
 
         ipfw('add', sport, 'check-state', 'ip',