carp observations

[Matthew George]

a couple of things I've noticed playing with carp ...


1) carp0 can't be destroyed, but there's no problem with carp[>0]

mdg# ifconfig carp0 192.168.3.0/24
mdg# ifconfig carp0 destroy
ifconfig: SIOCIFDESTROY: Invalid argument
mdg# ifconfig carp1 create
mdg# ifconfig carp1 destroy
[carp1 gone]


2) here I'm trying to setup carp for a network that isn't assigned to any
of my interfaces

mdg# ifconfig carp0 192.168.7.0/24
ifconfig: ioctl (SIOCAIFADDR): Can't assign requested address

somewhat expected, so I assign an address to dc3 and try again:

mdg# ifconfig dc3 192.168.7.1/24
mdg# ifconfig carp0 192.168.7.0/24
ifconfig: ioctl (SIOCAIFADDR): Can't assign requested address

interestingly enough, the same does not apply to a new carp interface.
once it sees I've assigned the address to dc3, it stops complaining.

mdg# ifconfig dc3 delete
mdg# ifconfig carp1 create
mdg# ifconfig carp1 inet 192.168.7.0/24
ifconfig: ioctl (SIOCAIFADDR): Can't assign requested address
mdg# ifconfig dc3 192.168.7.1/24
mdg# ifconfig carp1 inet 192.168.7.0/24
[created no problem]

so carp1 will work properly, but carp0 still won't:

mdg# ifconfig carp1 delete
mdg# ifconfig carp0 192.168.7.0/24
ifconfig: ioctl (SIOCAIFADDR): Can't assign requested address

I find that carp0 will be fine after a reboot as long as the ethernet
interface is configured before the carp interface, but a reboot does seem
to be necessary to recover.

-- 
Matthew George
SecureWorks Technical Operations