[SCSI] libfcoe: fcoe: fnic: add FIP VN2VN point-to-multipoint support

[SCSI] libfcoe: fcoe: fnic: add FIP VN2VN point-to-multipoint support

The FC-BB-6 committee is proposing a new FIP usage model called
VN_port to VN_port mode.  It allows VN_ports to discover each other
over a loss-free L2 Ethernet without any FCF or Fibre-channel fabric
services.  This is point-to-multipoint.  There is also a variant
of this called point-to-point which provides for making sure there
is just one pair of ports operating over the Ethernet fabric.

We add these new states:  VNMP_START, _PROBE1, _PROBE2, _CLAIM, and _UP.
These usually go quickly in that sequence.  After waiting a random
amount of time up to 100 ms in START, we select a pseudo-random
proposed locally-unique port ID and send out probes in states PROBE1
and PROBE2, 100 ms apart.  If no probe responses are heard, we
proceed to CLAIM state 400 ms later and send a claim notification.
We wait another 400 ms to receive claim responses, which give us
a list of the other nodes on the network, including their FC-4
capabilities.  After another 400 ms we go to VNMP_UP state and
should start interoperating with any of the nodes for whic we
receivec claim responses.  More details are in the spec.j

Add the new mode as FIP_MODE_VN2VN.  The driver must specify
explicitly that it wants to operate in this mode.  There is
no automatic detection between point-to-multipoint and fabric
mode, and the local port initialization is affected, so it isn't
anticipated that there will ever be any such automatic switchover.

It may eventually be possible to have both fabric and VN2VN
modes on the same L2 network, which may be done by two separate
local VN_ports (lports).

When in VN2VN mode, FIP replaces libfc's fabric-oriented discovery
module with its own simple code that adds remote ports as they
are discovered from incoming claim notifications and responses.
These hooks are placed by fcoe_disc_init().

A linear list of discovered vn_ports is maintained under the
fcoe_ctlr struct.  It is expected to be short for now, and
accessed infrequently.  It is kept under RCU for lock-ordering
reasons.  The lport and/or rport mutexes may be held when we
need to lookup a fcoe_vnport during an ELS send.

Change fcoe_ctlr_encaps() to lookup the destination vn_port in
the list of peers for the destination MAC address of the
FIP-encapsulated frame.

Add a new function fcoe_disc_init() to initialize just the
discovery portion of libfcoe for VN2VN mode.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>