On 3/14/22 14:40, Nick Mathewson wrote:
On Mon, Mar 14, 2022 at 3:18 PM Jim Newsome <jnewsome@torproject.org mailto:jnewsome@torproject.org> wrote:
On 3/14/22 11:44, Nick Mathewson wrote: <snip> > Currently Tor relays use a 4-byte timestamp (in seconds since the Unix > epoch) in their NETINFO cells. Notoriously, such a timestamp will > overflow on 19 January 2038. > > Let's get ahead of the problem and squash this issue now, by expanding > the timestamp to 8 bytes. (8 bytes worth of seconds will be long enough > to outlast the Earth's sun.) <snip> With all those extra bits, would there be any value to using a more granular time measure? e.g. microseconds?I don't think so, necessarily. We aren't doing full NTP here; in fact, we're just trying to detect clock skew that's big enough to break Tor. (Like, on the order of hours.) I don't think we'll get anything useful out of sub-second observations.
If not, would it be worth saving some bytes and only expanding to 5 bytes? (I know; it *feels* wrong, but I can't think of much real downside)Hm, possibly. One downside is that 5-byte decoder/encoder functions aren't exactly common, so we'd require everybody to build one. (Or to do something like u8 ts_high; u32 ts_low; )
Since the extra 3 bytes are only used once per connection attempt, I'm pretty comfortable letting them be useless until 36812 CE or whenever.
Makes sense to me. Thanks!