[SCSI] fnic: FIP VLAN Discovery Feature Support

FIP VLAN discovery discovers the FCoE VLAN that will be used by all other FIP
protocols as well as by the FCoE encapsulation for Fibre Channel payloads on
the established virtual link. One of the goals of FC-BB-5 was to be as
nonintrusive as possible on initiators and targets, and therefore FIP VLAN
discovery occurs in the native VLAN used by the initiator or target to
exchange Ethernet traffic. The FIP VLAN discovery protocol is the only FIP
protocol running on the native VLAN; all other FIP protocols run on the
discovered FCoE VLANs.

If an administrator has manually configured FCoE VLANs on ENodes and FCFs,
there is no need to use this protocol. FIP and FCoE will run over the
configured VLANs.

An ENode without FCoE VLANs configuration would use this automated discovery
protocol to discover over which VLANs FCoE is running.

The ENode sends a FIP VLAN discovery request to a multicast MAC address called
All-FCF-MACs, which is a multicast MAC address to which all FCFs listen.

All FCFs that can be reached in the native VLAN of the ENode are expected to
respond on the same VLAN with a response that lists one or more FCoE VLANs
that are available for the ENode's VN_Port login. This protocol has the sole
purpose of allowing the ENode to discover all the available FCoE VLANs.

Now the ENode may enable a subset of these VLANs for FCoE Running the FIP
protocol in these VLANs on a per VLAN basis. And FCoE data transactions also
would occur on this VLAN. Hence, Except for FIP VLAN discovery, all other FIP
and FCoE traffic runs on the selected FCoE VLAN.  Its only the FIP VLAN
Discovery protocol that is permitted to run on the Default native VLAN of the
system.

[**** NOTE ****]
We are working on moving this feature definitions and functionality to libfcoe
module. We need this patch to be approved, as Suse is looking forward to merge
this feature in SLES 11 SP3 release.  Once this patch is approved, we will
submit patch which should move vlan discovery feature to libfoce.

[Fengguang Wu <fengguang.wu@intel.com>: kmalloc cast removal]
Signed-off-by: Anantha Prakash T <atungara@cisco.com>
Signed-off-by: Hiral Patel <hiralpat@cisco.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>