bridge: Further decompose GRAB_OUR_PACKETS

[markj]

Summary

Introduce an inline function which consumes a packet known to be
destined for a particular interface. Generally, avoid introducing
macros with side effects.

Add a bridge_learn() helper instead of having the same code duplicated
into the local and forwarding cases.

Simplify some conditionals in bridge_forward().

No functional change intended.

[markj]

sys/net/if_bridge.c

2636

One small benefit of this approach is that we don't need to test the bridge interface type. There might be some other simplifications that are possible.

[zlei]

sys/net/if_bridge.c

2646

I wonder if we can have a hash map lladdr -> ifp to speed up lookups for bridge which have large quantity members.

[markj]

I'm not really looking at if_bridge anymore, so I'll drop this patch. If anyone wants to take it and change/improve it, please feel free.

sys/net/if_bridge.c

2646

Yes, that's probably a good idea. Even a flat array would be better than the linked list; now that the data path is protected by an epoch section, it should be pretty easy to implement resizing.