The source address in unicast DHCPv4 Request packets was found out
to be all zeros address 0.0.0.0. This address is only acceptable if
the destination is a multicast one, where the host in question is
acquiring a DHCP address lease. This is true for the DHCP Discover
and the initial DHCP Request message from the client towards the
server. As subsequent DHCP Request renewal messages are sent as
unicast to the server, the server will drop such packets.
Fix this issue by explicitely specifying what source IP address is
to be used, if none is specified, the all zeros address 0.0.0.0 is
used in multicast addresses. The source address in the other
unicast cases is identical to the 'ciaddr' in the DHCP message.
Signed-off-by: Patrik Flykt <patrik.flykt@intel.com>