On 8/2/15 6:09 PM, Tom Herbert wrote:
I was thinking whether to add skb_get_hash(), but then concluded the
>raw skb->hash seems fine in this case: we can directly access the hash
>w/o extra eBPF helper function call, it's filled out by many NICs on
>ingress, and in case the entropy level would not be sufficient, people
>can still implement their own specific sw fallback hash mix anyway.
>
Maybe we should add the skb_get_hash also? It doesn't as useful if
some scenarios we get a valid hash and in others not.
we also discussed whether it makes sense to expose l4_hash and sw_hash
bits as well. imo, seems a bit of overkill, since such call into sw hash
function like this exposes the logic of flow_dissector looking into
inner header. There are pros and cons. I think if we expose
flow_dissector it's cleaner to do it directly (instead of skb_get_hash).
Alternatively we can obfuscate skb_get_hash by calling it
'please compute some a hash on a packet somehow', but that will be
awkward to use. The programs can compute whatever hash they like anyway.
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