Apply restrictions on STP parameters based 802.1D 1998 standard.
* Fixes missing locking in set path cost ioctl
* Uses common code for both ioctl and sysfs
This is based on an earlier patch Sasikanth V but with overhaul.
Note:
1. It does NOT enforce the restriction on the relationship max_age and
forward delay or hello time because in existing implementation these are
set as independant operations.
2. If STP is disabled, there is no restriction on forward delay
3. No restriction on holding time because users use Linux code to act
as hub or be sticky.
4. Although standard allow 0-255, Linux only allows 0-63 for port priority
because more bits are reserved for port number.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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