Bridge Assurance functionality.

Bridge Assurance functionality.

1. Port type network ("setportnetwork" command) needs to be configured on ports on which bridge assurance functionality needs to be enforced. The functionality is enforced only for Operation Point-to-Point links and only when the operational version is RSTP/MSTP.
2. BPDU's are sent only on designated ports normally. For a network port type, BPDU's will be sent always and the port expects to receive BPDU's every hello time interval.
3. When a network port does not receive BPDU's in 3*hello_timer seconds from peer, the port is put in discarding state (with Bridge assurance inconsistency error in syslog), but BPDU's need to be sent out from the port every hello interval, though.
4. When an inconsistent bridge assurance port receives a BPDU later, the inconsistency is cleared and the port is transitioned to learning/forwarding as usual now.
5. Added hidden command "setdonttxmt" to not transmit BPDU's on demand, to test the functionality.

Signed-off-by: Satish Ashok <sashok@cumulusnetworks.com>
Signed-off-by: Vitalii Demianets <dvitasgs@gmail.com>
git-svn-id: svn://svn.code.sf.net/p/mstpd/code/trunk@46 fbe50366-0c72-4402-a84b-5d246361dba7