SIOCGIFADDR broken on 9.0-RC1?

Stefan Bethke stb at
Wed Nov 16 07:51:45 UTC 2011

Am 15.11.2011 um 23:35 schrieb GR:

> So, I switched to static assignement and it changes the behaviour (and "fixes" the "bug").
> My guess is that during the time waiting for the DHCP offer, all aliases are already configured on the network interface, and the IP address given by DHCP is added at the end of the tail.
> Is that a wanted behaviour? I find it dangerous (i.e. not exactly what a user is expecting).

A bit of background, as best I understand it and remember from Stevens:

Interfaces in BSD do not have a notion of "primary" and "additional" addresses; interfaces just have any number of addresses associated with them.  There's no inherent ordering in this list (except for how the current implementation seems to keep them in the order they were configured).

To be able to associate proper routes with interface addresses, the recommendation for multiple IPv4 addresses on an Ethernet interface is to have one of them have the proper netmask for the network, and configure the remainder with a netmask of  But that's solely for the benefit of the routing table; the interface itself doesn't really care.

Reading the rc.conf man page could give you the impression that there are primary and alias addresses, but the networking code doesn't really work like that.  The new ipv4_addrs_<interface> syntax exposes the actual behavior in a more direct way.

Jeremy gave you a hint on how to fix your immediate problem, but the real answer is that the program needs to be fixed that makes assumptions about meaning attached to the first configured IPv4 address.


Stefan Bethke <stb at>   Fon +49 151 14070811

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