The following bug was causing many issues for this branch in chutney:
In sr_state_get_start_time_of_current_protocol_run() we were using the
consensus valid-after to calculate beginning_of_current_round, but we were
using time(NULL) to calculate the current_round slot. This was causing time
sync issues when the consensus valid-after and time(NULL) were disagreeing on
what the current round is. Our fix is to use the consensus valid-after in both
places.
This also means that we are not using 'now' (aka time(NULL)) anymore in that
function, and hence we can remove that argument from the function (and its
callers). I'll do this in the next commit so that we keep things separated.
Furthermore, we fix a unittest that broke.
We only build a descriptor once, and we just re-encode it (and change its intro
points if needed) before uploading.
Hence we should set the revision counter before uploading, not during building.
The OPE cipher is tied to the current blinded key which is tied to the current
time period. Hence create the OPE cipher structure when we create a new
descriptor (and build its blinded key).
Now that the rev counter depends on the local time, we need to be more careful
in the unittests. Some unittests were breaking because they were using
consensus values from 1985, but they were not updating the local time
appropriately. That was causing the OPE module to complain that it was trying
to encrypt insanely large values.
To do so for a given descriptor, we use the "seconds since the SR protocol run"
started, for the SRV that is relevant to this descriptor. This is guaranteed to
be a positive value (since we need an SRV to be able to build a descriptor),
and it's also guaranteed to be a small value (since SRVs stop being listed on a
consensus after 48 hours).
We cannot use the "seconds since the time period started", because for the next
descriptor we use the next time period, so the timestamp would end up negative.
See [SERVICEUPLOAD] from rend-spec-v3.txt for more details.
To do so, we have to introduce a new `is_current` argument to a bunch of
functions, because to use "seconds since the SR protocol run" we need to know
if we are building the current or the next descriptor, since we use a different
SRV for each descriptor.
This is meant for use when encrypting the current time within the
period in order to get a monotonically increasing revision counter
without actually revealing our view of the time.
This scheme is far from the most state-of-the-art: don't use it for
anything else without careful analysis by somebody much smarter than
I am.
See ticket #25552 for some rationale for this logic.
