Re: When IGMPv3 router in EXCLUDE(X, Y) state receives TO_IN(A)

> Also that the current exclude list contains Y-A which is basically  
> those sources which should still be blocked. Only this set of  
> sources could also be queried.


There is no purpose in sending Group-and-Source-Specific queries for  
already blocked Source records (from 6.1):

A Group-and-Source Specific Query is used to verify there are no  
systems on a network which desire to receive traffic from a set of  
sources.  Group-and-Source Specific Queries list sources for a  
particular group which have been requested to no longer be forwarded.

Further, already blocked Source records do no have running timers --  
there is no Source record state to query for, there is no Source  
record state to refresh, there is no Source record timer to lower,  
there is no Source record timer to update, etc. There IS Group record  
state to query for, there is Group record state to refresh, there is a  
Group record timer to lower, there is a Group record timer to update,  
etc.

And if you did do something like Q(G,Y-A) in place of Q(G), there  
would be problems refreshing membership for hosts having a filter mode  
of EXCLUDE and an empty source list, there would be problems handling  
the Group timer on the elected querier, and there would be problems  
handling the Group timer on the non-elected routers.