improvment suggestion for NM

[Paul Ionescu <i_p_a_u_l yahoo com>]

Hi Dan,

More thoughts:
It would be nice and more robust to have some sort of checkup of the
default gateway after important changes.

Some examples:
1) A new net card is hot plugged. Various pieces of software will jump to
configure my new card, not playing nice with NM, possibly ruining the
default route. Here NM should check that the default gateway is still
there after configuring the newly hot plugged card. If is not there, we
should put it again.

2) We start NM with a configuration without default gateway but a a
netcard is already active. Here NM will not do anything, leaving the box
without default gw. 
If there is no default gw, NM should start to activate the netcard from
scratch, not leaving as it is. 

Also here can be an improvement for selecting the correct IP address of
a card if is configured static. The improvement is: select the static ip
address and gw, and test to ping the gw. If we cannot ping the gw,
fallback to dhcp even if it is static configured. If dhcp does not answer
try ask mDNS for default gw, and if still nothing try next valid
interface. 
If this is last interface, inform user that there is no net
connectivity (dbus + something ?) and if he want to setup a private net
(169.bla) or something.

Thanks,
Paul