Does the ordering of the fib_table_dump or /proc/net/fib_trie matter?

I am considering reversing the order of any non-lookup traversal of the fib_trie so that it starts at the last node and works it's way up toward the first node. This would make it so that all walks using the parent pointer all go in the same direction.

The problem right now is that leaf_walk_rcu and a couple of other iterators traverse the trie in one direction grabbing the next child (child++) of the parent, while fib_table_lookup is traversing the list grabbing a previous child (child & (child - 1)) of the parent. It makes things a bit ugly for RCU as we have to have the node fully populated before we can start updating the parent pointers on the children.

I want to have them both moving in the same direction so the fib_table_lookup would remain the same, but the leaf_walk_rcu and others would walk from the last child to the first (child--) and as a result when I assemble a tnode in inflate or halve I would be able to populate children from 0 to ((1 << tn->bits) - 1) without having to worry about any iterators walking into uninitialized memory.

The question I have is if that would screw up any user-space apps. I know ip route can dump the list via "ip route show". I'm just wondering if there would be any problem with default being the last entry instead of the first entry?

- Alex

From: Alexander Duyck <[email protected]>
Date: Tue, 06 Jan 2015 12:30:06 -0800

The ordering already changed once when we went from fib_hash to fib_trie, nobody should depend upon the ordering.

Okay good to hear. I kind of thought that was the case, but I wanted to make sure before I went too far down this rabbit hole.

Thanks.

- Alex