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Re: NetBSD systems as half-routers for P2P or VPN links

> The "protocol configuration" == "address configuration" has some very
> annoying side effects.  It is one of the (short list of) reasons why
> an IPv4 DHCP client can't use the kernel UDP stack to send and
> receive its UDP packets, and instead has to resort to BPF and roll
> its own IP/UDP;

How could the anything use the kernel UDP stack when the interface has
no addresses?  It can't even tell what packets are intended for it
under such circumstances.  It is not possible to send an IP packet
without putting _something_ in the ip_src and ip_dst fields.  Using IP
without configuring an address means incoming traffic can't work
because the kernel has no way to tell whether a packet is intended for
it or not; outgoing connectionless traffic could in principle work, but
would require userland to explicitly specify the source address for
each packet (since the kernel can't assign one as usual).

> it would need to put an IPv4 address on the interface to configure it
> up for sending and receiving the IPv4 packets

Oddly enough, I've seen addresses configured with while DHCP is
trying to get an address on them.

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