[Xorp-hackers] OLSR assert

[Bruce Simpson]

Bruce Simpson wrote:
> Ben Greear wrote:
>   
>> The reset_twohop_mpr_state counts neighbors that are strict and reachable.
>> But, the consider_poorly_covered method checks for reachability == 1.
>> In the log below, neighbor 10.7.7.7 is not counted in poorly_covered.
>> Should we maybe check for reachability() > 0 instead of == 1?
>>   
>>     
>
> Off the top of my head, for classical OLSR, as specified in the RFC, it 
> needs to be covered by a minimum of 1 neighbour, in terms of links.
>
> I don't have the code in front of me, obviously a test of reachability 
> == 1 would be naive. If the fix is that simple, that's great.
>   

This is logically correct, a poorly covered N2 is one which has 
reachability of 1. When computing the MPR set, N which are the only 
means of reaching those N2 need to be considered first.

It's the is_essential_mpr() predicate (within minimize_mpr_set()) which 
is responsible for making sure that those critical links aren't thrown 
out, when pruning the MPR set to reduce flooding.

Most of the work involved in computing MPRs upfront is done to limit 
(minimize?) the work minimize_mpr_set() has to do.