[OLSR-users] Default Forwarding Algorithm in OLSR

[lolo]

Hello all

I'm really puzzled about section 3.4.1 of RFC3626 and ask for light from 
OLSR gurus.

Could someone give me the reason why the node have to record and check 
the "consideration for forwarding a message" by checking that the 
message come form a symetric neighbor before checking, again, that the 
node sending the message is a MPR selector or not ? Why not checking in 
the first place if it's a MPR selector or not ? Why the two tests ?

Here what I understand from the RFC :

If the message is received from a neighbor that is not symetric the 
message is dropped and the "trace" of the message is not recorded

If the message is received the first time from a symetric neighbor that 
is not a MPR selector the "trace" of the message is registered in the 
Duplicate Set, the field D_retransmitted is leaved false and the message 
is not relayed

If the message is received the first time from a MPR selector the 
"trace" of the message is registered in the Duplicate Set, the field 
D_retransmitted is set to true, and the message is relayed

If the message if received a second time on the same interface it is 
discarded (already relayed or not).
If the message if received a second time on another interface :
 check that the neighbor is symetric then :
  if message is already relayed (D_retransmitted == true) then messsage 
is discarded and the interface address is *not* registered in the 
duplicated set
   elseif the sender is a MPR selector the message is relayed and 
interface is added to duplicate set.

Here what i  naively think could be done :

Change section §4.1 of section 3.4 from RFC3626 :
check that the message has not already been received on the same 
interface for so test :
if message not already registered in Duplicate Set, or already 
registered but on another interface then goto section 3.4.1
if message already registered on that interface then drop the message

Section 3.4.1 :
register the message in the Duplicated Set (or only add that particular 
interface if enough)
check if the sender is a MPR Selector
if not then do not relay the message
else relay the message

I've missed something, that is sure, because there is no more need of 
the D_retransmitted field, but i dont see what and where.

TIA for any hints or links

Laurent