[lwip-devel] [bug #48162] Off-link RA prefix with bit A set is ignored resulting in no address

[Jan Breuer]

Follow-up Comment #1, bug #48162 (project lwip):

It seems to be much deeper problem. More reading in RFC 5942.

Bit L tells if the prefix is on-link or not. ip6_route should look on
prefix_list and not address list to determine, if it can send a packet
directly to that interface or not.

Bit A tells that there can be done address autoconfiguration using this prefix
but it is completely independent from bit L.

So the interface can have
- address using off-link prefix
- different on-link prefix without address
and this configuration is completely legal.

Sending packet matching on-link prefix must be done directly.
Sending packet matching off-link prefix must be done using router.

LwIP assumes that all Prefix Information Options ar used with both L and A
bits set and all other combinations are ignored. This cause two bugs
 - off-link prefixes are not used for addres autoconfiguration
 - on-link prefixes without address are not used for direct communication


---------

Off-link prefix can be used in environment, where you need to isolate all
nodes and you need to force all nodes to use router. Every communication is
done by the router and it determines whether you are allowed to communicate
with another node or not.

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