Comment 10 for bug 1529815

RFC 4390 from 2006:

https://tools.ietf.org/html/rfc4390
(Dynamic Host Configuration Protocol (DHCP) over InfiniBand) also stipulates:

As described above, the link-layer address is unavailable to the DHCP
   server because the link-layer address is larger than the "chaddr"
   field length. As a result, the server cannot unicast its reply to
   the client. Therefore, a DHCP client MUST request that the server
   send a broadcast reply by setting the BROADCAST flag when IPoIB
   Address Resolution Protocol (ARP) is not possible, i.e., in
   situations where the client does not know its IP address.

   [RFC1542] discourages the use of a broadcast reply. But in the case
   of IPoIB, this is a necessity because the server does not receive the
   link-layer address.