Felix Fietkau <nbd@xxxxxxxx> writes: > On 2020-12-17 12:54, Toke Høiland-Jørgensen wrote: >> Felix Fietkau <nbd@xxxxxxxx> writes: >> >>> Depending on the source, a hardware calculated hash may not provide the >>> same level of collision resistance. >> >> This seems like it would have performance implications? >> >> Also, this can potentially discard information from tunnels that >> preserve the hash before encapsulation (we added support for this to >> Wireguard which had some nice effects on queueing of encapsulated >> traffic). > If the hash was calculated in software using the flow dissector, it will > be preserved, even if it went through a few virtual interfaces. > The only hashes discarded are hardware generated ones. Yeah, but I was thinking something like: Packet comes in with HW hash -> gets encapsulated (preserving the hash) -> gets to mac80211 which discards the HW hash. So now you're replacing a (possibly bad-quality) HW hash with a software hash of the *outer* encapsulation header... -Toke
