As discussed in recent days, MASQUERADE target handling of device events
is broken in a couple of ways:

1) when ppp interfaces cycle, conntracks with old ip addresses are not
   flushed

2) an 'ip addr add' on an interface used for masquerading flushes all
   conntracks associated with that interface

The below patch addresses these issues by changing from using ifindex
comparisons to verifying that the masquerading ip still exists on the
box.

To achieve this, two changes were required to core networking code (thus
the linux-net cc):

1) export inet_confirm_addr

2) change inet_ifa_match to use ifa_local instead of ifa_address.
   Since ifa_local != ifa_address on ppp interfaces, inet_ifa_match
   could not be used to verify ppp interface addresses without
   this change.

Comments?

Phil