packetdrill: consider relative time tolerance for timestamping

Packetdrill checks difference between expected time and observed time
using a tolerance, which is set as the higher of a fixed value
(tolerance_usecs) or a percentage(tolerance_percent) times duration.

Extend this check for SCM_TIMESTAMPING records.

gtests/net/packetdrill/run.c

@@ -92,6 +92,7 @@ struct state *state_new(struct config *config,
 	state->code = code_new(config);
 	state->fds = NULL;
 	state->num_events = 0;
+	state->last_tcp_timestamp_usecs = NO_TIME_RANGE;
 	return state;
 }
 
@@ -181,22 +182,17 @@ int verify_time(struct state *state, enum event_time_t time_type,
 	s64 expected_usecs_end = script_usecs_end -
 		state->script_start_time_usecs;
 	s64 actual_usecs = live_usecs - state->live_start_time_usecs;
-	long tolerance_usecs = state->config->tolerance_usecs;
+	s64 tolerance_usecs;
 
 	DEBUGP("expected: %.3f actual: %.3f  (secs)\n",
 	       usecs_to_secs(script_usecs), usecs_to_secs(actual_usecs));
 
 	if (time_type == ANY_TIME)
 		return STATUS_OK;
 
-	if (last_event_usecs != NO_TIME_RANGE) {
-		s64 delta = script_usecs - last_event_usecs;
-		long dynamic_tolerance;
+	tolerance_usecs = get_tolerance_usecs(state, script_usecs,
+					      last_event_usecs);
 
-		dynamic_tolerance = (state->config->tolerance_percent / 100.0) * delta;
-		if (dynamic_tolerance > tolerance_usecs)
-			tolerance_usecs = dynamic_tolerance;
-	}
 	if (time_type == ABSOLUTE_RANGE_TIME ||
 	    time_type == RELATIVE_RANGE_TIME) {
 		DEBUGP("expected_usecs_end %.3f\n",

gtests/net/packetdrill/run.h

@@ -105,6 +105,7 @@ struct state {
 	s64 script_start_time_usecs;	/* time of first event in script */
 	s64 script_last_time_usecs;	/* time of previous event in script */
 	s64 live_start_time_usecs;	/* time of first event in live test */
+	s64 last_tcp_timestamp_usecs;	/* time of previous tcp_timestamp */
 	int num_events;			/* events executed so far */
 };
 
@@ -161,6 +162,26 @@ static inline s64 last_event_time_usecs(struct state *state)
 			state->last_event->time_usecs;
 }
 
+/*
+ * Return the greater between static and dynamic tolerance
+ * Static tolerance: state->config->tolerance_usecs
+ * Dynamic tolerance: state->config->tolerance_percent * time_delta
+ */
+static inline s64 get_tolerance_usecs(struct state *state, s64 script_usecs,
+	s64 last_event_usecs)
+{
+	s64 tolerance_usecs = state->config->tolerance_usecs;
+
+	if (last_event_usecs != NO_TIME_RANGE) {
+		s64 delta = script_usecs - last_event_usecs;
+		s64 d_tol = (state->config->tolerance_percent / 100.0) * delta;
+
+		if (d_tol > tolerance_usecs)
+			tolerance_usecs = d_tol;
+	}
+	return tolerance_usecs;
+}
+
 /*
  * See if something that happened at the given actual live wall time
  * in microseconds happened reasonably close to the time at which we

gtests/net/packetdrill/run_packet.c

@@ -1224,21 +1224,15 @@ static int verify_outbound_tcp_option(
 	struct config *config = state->config;
 	u32 script_ts_val, actual_ts_val;
 	int ts_val_tick_usecs;
-	long tolerance_usecs;
-	double dynamic_tolerance;
-	s64 delta;
+	s64 tolerance_usecs;
 
-	tolerance_usecs = config->tolerance_usecs;
 	/* Note that for TCP TS, we do not want to compute the tolerance based
 	* on last event (as we do in verify_time())
 	* last event might have happened few ms in the past.
 	* What matters here is the cumulative time (from the beginning of the test)
 	*/
-	delta = state->event->time_usecs - state->script_start_time_usecs;
-
-	dynamic_tolerance = (config->tolerance_percent / 100.0) * delta;
-	if (dynamic_tolerance > tolerance_usecs)
-		tolerance_usecs = dynamic_tolerance;
+	tolerance_usecs = get_tolerance_usecs(state, state->event->time_usecs,
+						state->script_start_time_usecs);
 
 	switch (actual_option->kind) {
 	case TCPOPT_EOL:
@@ -1255,9 +1249,10 @@ static int verify_outbound_tcp_option(
 		 */
 		if (ts_val_tick_usecs &&
 		    ((abs((s32)(actual_ts_val - script_ts_val)) *
-		      ts_val_tick_usecs) >
-		     tolerance_usecs)) {
-			asprintf(error, "bad outbound TCP timestamp value, tolerance %ld", tolerance_usecs);
+		      ts_val_tick_usecs) > tolerance_usecs)) {
+			asprintf(error,
+				"bad outbound TCP timestamp value, tolerance %lld",
+				tolerance_usecs);
 			return STATUS_ERR;
 		}
 		break;

gtests/net/packetdrill/run_system_call.c

@@ -702,9 +702,12 @@ static bool scm_timestamping_expect_eq(struct state *state,
 		s64 exp_usecs = script_time_to_live_time_usecs(state,
 			timespec_to_usecs(&expected->ts[i]));
 		s64 actual_usecs = timespec_to_usecs(&actual->ts[i]);
+		s64 tolerance_usecs = get_tolerance_usecs(state, actual_usecs,
+				state->last_tcp_timestamp_usecs);
+		state->last_tcp_timestamp_usecs = actual_usecs;
+
 		/* difference exceeds configured timing tolerance */
-		if (llabs(exp_usecs - actual_usecs) >
-		    state->config->tolerance_usecs) {
+		if (llabs(exp_usecs - actual_usecs) > tolerance_usecs) {
 			asprintf(error,
 				 "Bad timestamp %d in scm_timestamping %d: "
 				 "expected=%lld (%lld) actual=%lld (%lld) "