If i have a server which has a management-only interface which is usually down, in versions of Ubuntu before 11.10, I could configure that ethernet interface in /etc/network/interfaces, and dhclient would try forever to get an address.
I believe this is a regression that was introduced in the fix for bug #838968 , where the '-1' parameter was introduced to dhclient3's invocation in ifupdown.
While I do think we should report errors, we should also retry this *forever* since it may be the only way a system can be reached *to see that error*.
* bug 838968: static-network-up event does not wait for interfaces to have an address
* bug 974284: invoking dhclient3 with -1 causes issue if no dhcp server available