max MTU for fwip device.

[Alexander Nedotsukov]

>>>Interesting. The specification for IPv6 on firewire is clearer:
>>>
>>>  The default MTU size for IPv6 packets on an IEEE1394 network is 1500
>>>  octets.  This size may be reduced by a Router Advertisement [DISC]
>>>  containing an MTU option which specifies a smaller MTU, or by manual
>>>  configuration of each node.  If a Router Advertisement received on an
>>>  IEEE1394 interface has an MTU option specifying an MTU larger than
>>>  1500, or larger than a manually configured value, that MTU option may
>>>  be logged to system management but MUST be otherwise ignored.  The
>>>  mechanism to extend MTU size between particular two nodes is for
>>>  further study.
>>> 
>>>
>>>      
>>>
>>Mmm. I still do not see any prohibition of MTU size > 1500. What I see 
>>here is definition of automatic MTU adjustment. It's stated that ATM MTU 
>>size may be only reduced by such mechanism. Am I right?
>>So manual configuration of interface for MTU size > 1500 violates nothing.
>>    
>>
>
>Of course - I certainly don't want to stop people from configuring an
>MTU size > 1500. I just think that for the compiled in default, we
>should go with the spec for now.
>
>  
>
I do not object default MTU either. But the problem is we have hardcoded 
1500 limit in SIOCSIFMTU  ioctl handler ATM. Check sys/net/if_fwsubr.c ;-)