commit 3f514fe3b1d217c80edb1524976203bc535f9502 Author: Nick Mathewson nickm@torproject.org Date: Thu Apr 12 13:11:35 2018 -0400

Accept small hops backward in the monotonic timer. --- src/common/token_bucket.c | 8 ++++++++ src/test/test_bwmgt.c | 7 ++++++- 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/common/token_bucket.c b/src/common/token_bucket.c index abb050183..6af298214 100644 --- a/src/common/token_bucket.c +++ b/src/common/token_bucket.c @@ -120,6 +120,14 @@ token_bucket_refill(token_bucket_t *bucket, uint32_t now_ts) { const uint32_t elapsed_ticks = (now_ts - bucket->last_refilled_at_ts); + if (elapsed_ticks > UINT32_MAX-(300*1000)) { + /* Either about 48 days have passed since the last refill, or the + * monotonic clock has somehow moved backwards. (We're looking at you, + * Windows.). We accept up to a 5 minute jump backwards as + * "unremarkable". + */ + return 0; + } const uint32_t elapsed_steps = elapsed_ticks / TICKS_PER_STEP;

if (!elapsed_steps) { diff --git a/src/test/test_bwmgt.c b/src/test/test_bwmgt.c index 7bcfcf7fe..2428b1505 100644 --- a/src/test/test_bwmgt.c +++ b/src/test/test_bwmgt.c @@ -178,8 +178,13 @@ test_bwmgt_token_buf_refill(void *arg) tt_int_op(b.read_bucket, OP_GT, 8*KB-200); tt_int_op(b.read_bucket, OP_LT, 8*KB+200);

- // a ridiculous amount of time passes + // We step a second backwards, and nothing happens. tt_int_op(0, OP_EQ, token_bucket_refill(&b, START_TS + SEC*64)); + tt_int_op(b.read_bucket, OP_GT, 8*KB-200); + tt_int_op(b.read_bucket, OP_LT, 8*KB+200); + + // A ridiculous amount of time passes. + tt_int_op(0, OP_EQ, token_bucket_refill(&b, INT32_MAX)); tt_int_op(b.read_bucket, OP_EQ, b.burst);

done: