NM 0.7 connection sharing

[Dan Williams <dcbw redhat com>]

Hi,

After some discussion in a related thread on fedora-devel, I've thought
through the WiFi connection sharing a bit more, and been schooled on a
few things.

Mac OS X provides a full infrastructure-mode network when sharing an
internet connection over wireless.  It also provides DHCP to clients of
that wifi network, and uses addresses in the 10.x.x.x space.

Unfortunately, given the current driver situation, NM on Linux won't be
able to do the same thing, since few drivers support master mode well at
this time.  Therefore, NM 0.7 will:

1) as the _originator_ of a wireless network, either by sharing a
connection or creating a new wireless network, use 802.11 Ad-Hoc and
provide a DHCP server (see below)

2) require opt-in to get IPv4 LL on device types known to usually use
DHCP, requiring the user to pick between Auto-IP and DHCP (ie, Auto-IP
and DHCP will be mutually exclusive)

3) Perform DHCP by default on Ad-Hoc networks, unless the user has opted
into Auto-IP in the connection editor

4) use dnsmasq as the DHCP server for shared connections.  The ISC dhcpd
uses 20MB of RAM when running and that's just unacceptable.  dnsmasq
also provides proxied DNS, which is a nice bonus.

Dan