Hi Michael, On Tue, Mar 1, 2022 at 6:17 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > Hmm okay, so it's a performance optimization... some batching then? Do > you really need to worry about every packet? Every 64 packets not > enough? Packets are after all queued at NICs etc, and VM fork can > happen after they leave wireguard ... Unfortunately, yes, this is an "every packet" sort of thing -- if the race is to be avoided in a meaningful way. It's really extra bad: ChaCha20 and AES-CTR work by xoring a secret stream of bytes with plaintext to produce a ciphertext. If you use that same secret stream and xor it with a second plaintext and transmit that too, an attacker can combine the two different ciphertexts to learn things about the original plaintext. But, anyway, it seems like the race is here to stay given what we have _currently_ available with the virtual hardware. That's why I'm focused on trying to get something going that's the least bad with what we've currently got, which is racy by design. How vitally important is it to have something that doesn't race in the far future? I don't know, really. It seems plausible that that ACPI notifier triggers so early that nothing else really even has a chance, so the race concern is purely theoretical. But I haven't tried to measure that so I'm not sure. Jason
