> I think [dhcp uses bpf] because it needs to know which interface the
> packet arrived on, and there traditionally hasn't been a way to find
> this out about UDP packets.  [...]
> 
> If NetBSD already has a way to identify the incoming interface for an
> IP datagram it could probably be put to use.

It looks as though setting IP_RECVIF with setsockopt (level IPPROTO_IP,
if I've read the code right) should do this - search for IP_RECVIF and
INP_RECVIF in /sys/netinet for full details.

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