Re: [Bug 120441] af_packet no longer uses symmetric hashing

quoted

Isn't a symmetric hashing for af-packet something very fundamental?
Looks much more like a bug to me.

I agree it would be useful resp. fundamental. I'm not quite sure whether
PACKET_FANOUT_HASH always had this guarantee since the initial
implementation

It is based on rxhash, which is intended to have this property. See for
instance the commit messages from commit b249dcb82d32 ("rps:
consistent rxhash")

"In case we compute a software skb->rxhash, we can generate a
consistent hash : Its value will be the same in both flow directions."

commit 6862234238e8 ("net: small bug on rxhash calculation") also
explicitly refers to this property.

f.e. depending on whether the skb got fanout demuxed from RX or TX paths,
you would either use a hw hash or it would have gone through the kernel's
(predecessor) flow dissector

It's quite possible that not all hardware hash implementations do the
right thing, indeed.