Some EoIB implementations utilise an EoIB-to-Ethernet gateway device
that does not perform a FullMember join to the multicast group for the
EoIB broadcast domain.  This has various exciting side-effects, such
as requiring every EoIB node to send every broadcast packet twice.

As an added bonus, the gateway may also break the EoIB MAC address to
GID mapping protocol by sending Ethernet-sourced packets from the
wrong QPN.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Some EoIB implementations require each individual EoIB node to create
the multicast group for the EoIB broadcast domain.

It is left as an exercise for the interested reader to determine how
such an implementation might ever allow the parameters of such a
multicast group to be changed without requiring a simultaneous upgrade
of every driver on every operating system on every machine currently
attached to the fabric.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

EoIB is a fairly simple protocol in which raw Ethernet frames
(excluding the CRC) are encapsulated within Infiniband Unreliable
Datagrams, with a four-byte fixed EoIB header (which conveys no actual
information).  The Ethernet broadcast domain is provided by a
multicast group, similar to the IPoIB IPv4 multicast group.

The mapping from Ethernet MAC addresses to Infiniband address vectors
is achieved by snooping incoming traffic and building a peer cache
which can then be used to map a MAC address into a port GID.  The
address vector is completed using a path record lookup, as for IPoIB.
Note that this requires every packet to include a GRH.

Add basic support for EoIB devices.  This driver is substantially
derived from the IPoIB driver.  There is currently no mechanism for
automatically creating EoIB devices.

Signed-off-by: Michael Brown <mcb30@ipxe.org>