The function send_packet, in
/usr/src/usr.sbin/dhcpd/bpf.c, makes a call to
writev(2), which returns -1 and sets
errno(2) upon error.
The errno variable in this case, was set to ENOBUFS, indicating the kernel is unable to allocate any additional memory buffers (i.e:
mbuf(9)'s).
Now.. if increasing the UDP buffers didn't help.. net.bpf.bufsize and net.bpf.maxbufsize might need to be increased, but I'm not 100% sure about that.
That's all I can think of.. mailing list archives might also be worth reading as well.
@DutchDaemon, Stop giving FreeBSD advice in the OpenBSD sections.