unless relay agent (gaddr) is specified, dhcp requests need to
taget a local ip address on the incoming interface or broadcast.
clients might have multiple ethernet interfaces, so we need to
check if any of the ether= attributes in ndb matches. this is
done by passing lookupip() the attribute name and a expected
value and if a match is found, set Info.indb = 1.
remove tohex(), use encodefmt instead. avoid dynamcic allocation.
include interface device in log messages.
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