AP: Use monotonic time for STA accounting

For type-safety, make sta->acct_session_start a struct os_reltime
and then use monotonic time for accounting. For RADIUS reporting,
continue to use wall clock time as specified by RFC 2869, but for
the session time use monotonic time.

Interestingly, RFC 2869 doesn't specify a timezone, so the value
is somewhat arbitrary.

Signed-hostap: Johannes Berg <johannes.berg@intel.com>

src/ap/accounting.c

@@ -202,7 +202,6 @@ static void accounting_interim_update(void *eloop_ctx, void *timeout_ctx)
 void accounting_sta_start(struct hostapd_data *hapd, struct sta_info *sta)
 {
 	struct radius_msg *msg;
-	struct os_time t;
 	int interval;
 
 	if (sta->acct_session_started)
@@ -213,8 +212,7 @@ void accounting_sta_start(struct hostapd_data *hapd, struct sta_info *sta)
 		       "starting accounting session %08X-%08X",
 		       sta->acct_session_id_hi, sta->acct_session_id_lo);
 
-	os_get_time(&t);
-	sta->acct_session_start = t.sec;
+	os_get_reltime(&sta->acct_session_start);
 	sta->last_rx_bytes = sta->last_tx_bytes = 0;
 	sta->acct_input_gigawords = sta->acct_output_gigawords = 0;
 	hostapd_drv_sta_clear_stats(hapd, sta->addr);
@@ -244,6 +242,7 @@ static void accounting_sta_report(struct hostapd_data *hapd,
 	struct radius_msg *msg;
 	int cause = sta->acct_terminate_cause;
 	struct hostap_sta_driver_data data;
+	struct os_reltime now_r, diff;
 	struct os_time now;
 	u32 gigawords;
 
@@ -258,9 +257,11 @@ static void accounting_sta_report(struct hostapd_data *hapd,
 		return;
 	}
 
+	os_get_reltime(&now_r);
 	os_get_time(&now);
+	os_reltime_sub(&now_r, &sta->acct_session_start, &diff);
 	if (!radius_msg_add_attr_int32(msg, RADIUS_ATTR_ACCT_SESSION_TIME,
-				       now.sec - sta->acct_session_start)) {
+				       diff.sec)) {
 		wpa_printf(MSG_INFO, "Could not add Acct-Session-Time");
 		goto fail;
 	}

src/ap/ieee802_1x.c

@@ -1951,7 +1951,7 @@ int ieee802_1x_get_mib_sta(struct hostapd_data *hapd, struct sta_info *sta,
 {
 	int len = 0, ret;
 	struct eapol_state_machine *sm = sta->eapol_sm;
-	struct os_time t;
+	struct os_reltime diff;
 
 	if (sm == NULL)
 		return 0;
@@ -2066,7 +2066,7 @@ int ieee802_1x_get_mib_sta(struct hostapd_data *hapd, struct sta_info *sta,
 	len += ret;
 
 	/* dot1xAuthSessionStatsTable */
-	os_get_time(&t);
+	os_reltime_age(&sta->acct_session_start, &diff);
 	ret = os_snprintf(buf + len, buflen - len,
 			  /* TODO: dot1xAuthSessionOctetsRx */
 			  /* TODO: dot1xAuthSessionOctetsTx */
@@ -2081,7 +2081,7 @@ int ieee802_1x_get_mib_sta(struct hostapd_data *hapd, struct sta_info *sta,
 			  (wpa_key_mgmt_wpa_ieee8021x(
 				   wpa_auth_sta_key_mgmt(sta->wpa_sm))) ?
 			  1 : 2,
-			  (unsigned int) (t.sec - sta->acct_session_start),
+			  (unsigned int) diff.sec,
 			  sm->identity);
 	if (ret < 0 || (size_t) ret >= buflen - len)
 		return len;

src/ap/sta_info.h

@@ -78,7 +78,7 @@ struct sta_info {
 
 	u32 acct_session_id_hi;
 	u32 acct_session_id_lo;
-	time_t acct_session_start;
+	struct os_reltime acct_session_start;
 	int acct_session_started;
 	int acct_terminate_cause; /* Acct-Terminate-Cause */
 	int acct_interim_interval; /* Acct-Interim-Interval */