Re: Allocating AF constants for vendors.

I second Max. If you are going to introduce a bunch of AF_* constants into the tree you have to be very careful as AF_MAX is used to size arrays and figure out how many radix trie heads to allocate.

It could be argued this wastes a bunch of CPU time and memory, though I speculate 'not much' at the moment; I am just a bit concerned that we have ifnet->if_afdata which is also sized based on AF_MAX, 37, even though most of the protocols in it are never attached to ifnets.

The only domain I've seen which really uses if_afdata is PF_INET6. PF_INET does not use it at all. In my opinion, there are structures per-family per-ifnet which really belong hung-off ifnet on a 1:1 basis and would simplify some of the lazy allocations we have further down in the stack.

If AF_MAX increases significantly so will wasted memory. If you are going to make any significant changes here, please considering moving this stuff to a more dynamic method of allocation.

On the other hand, if you don't need to reference these constants in the kernel at all, and they will all exist beyond AF_MAX, then you can disregard what I've said and append them to the rest of the list.

That is pretty much what happens for the libpcap/bpf DLT constants (which are not an exact analogue of the AF constants - we don't allocate other, larger kernel structures based on their value).

regards,
BMS
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