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Accept small hops backward in the monotonic timer.

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This commit is contained in:
Nick Mathewson 2018-04-12 13:11:35 -04:00
parent c63761a0a6
commit 3f514fe3b1
2 changed files with 14 additions and 1 deletions
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8
src/common/token_bucket.c
View file

@ -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) {

7
src/test/test_bwmgt.c
View file

@ -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: