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Micah Elizabeth Scott
23f4a28f97
This started as a response to ticket #40792 where Coverity is complaining about a potential year 2038 bug where we cast time_t from approx_time() to uint32_t for use in token_bucket_ctr. There was a larger can of worms though, since token_bucket really doesn't want to be using wallclock time here. I audited the call sites for approx_time() and changed any that used a 32-bit cast or made inappropriate use of wallclock time. Things like certificate lifetime, consensus intervals, etc. need wallclock time. Measurements of rates over time, however, are better served with a monotonic timer that does not try and sync with wallclock ever. Looking closer at token_bucket, its design is a bit odd because it was initially intended for use with tick units but later forked into token_bucket_rw which uses ticks to count bytes per second, and token_bucket_ctr which uses seconds to count slower events. The rates represented by either token bucket can't be lower than 1 per second, so the slower timer in 'ctr' is necessary to represent the slower rates of things like connections or introduction packets or rendezvous attempts. I considered modifying token_bucket to use 64-bit timestamps overall instead of 32-bit, but that seemed like an unnecessarily invasive change that would grant some peace of mind but probably not help much. I was more interested in removing the dependency on wallclock time. The token_bucket_rw timer already uses monotonic time. This patch converts token_bucket_ctr to use monotonic time as well. It introduces a new monotime_coarse_absolute_sec(), which is currently the same as nsec divided by a billion but could be optimized easily if we ever need to. This patch also might fix a rollover bug.. I haven't tested this extensively but I don't think the previous version of the rollover code on either token bucket was correct, and I would expect it to get stuck after the first rollover. Signed-off-by: Micah Elizabeth Scott <beth@torproject.org>