prop224: Compute start time of next time period.

2 files changed, 17 insertions, 0 deletions

diff --git a/src/or/hs_common.c b/src/or/hs_common.c
index 01bd204e11..0d81063cf7 100644
--- a/src/or/hs_common.c
+++ b/src/or/hs_common.c
@@ -23,6 +23,7 @@
 #include "rendservice.h"
 #include "router.h"
 #include "shared_random.h"
+#include "shared_random_state.h"
 
 /* Ed25519 Basepoint value. Taken from section 5 of
  * https://tools.ietf.org/html/draft-josefsson-eddsa-ed25519-03 */
@@ -216,6 +217,21 @@ hs_get_next_time_period_num(time_t now)
   return hs_get_time_period_num(now) + 1;
 }
 
+/* Return the start time of the upcoming time period based on <b>now</b>. */
+time_t
+hs_get_start_time_of_next_time_period(time_t now)
+{
+  uint64_t time_period_length = get_time_period_length();
+
+  /* Get start time of next time period */
+  uint64_t next_time_period_num = hs_get_next_time_period_num(now);
+  uint64_t start_of_next_tp_in_mins = next_time_period_num *time_period_length;
+
+  /* Apply rotation offset as specified by prop224 section [TIME-PERIODS] */
+  unsigned int time_period_rotation_offset = sr_state_get_phase_duration();
+  return start_of_next_tp_in_mins * 60 + time_period_rotation_offset;
+}
+
 /* Create a new rend_data_t for a specific given <b>version</b>.
  * Return a pointer to the newly allocated data structure. */
 static rend_data_t *
diff --git a/src/or/hs_common.h b/src/or/hs_common.h
index cbf1ac113d..519485d576 100644
--- a/src/or/hs_common.h
+++ b/src/or/hs_common.h
@@ -195,6 +195,7 @@ void hs_get_subcredential(const ed25519_public_key_t *identity_pk,
 
 uint64_t hs_get_time_period_num(time_t now);
 uint64_t hs_get_next_time_period_num(time_t now);
+time_t hs_get_start_time_of_next_time_period(time_t now);
 
 link_specifier_t *hs_link_specifier_dup(const link_specifier_t *lspec);