RADIUS: Add Acct-Delay-Time into accounting messages

This tells to the server how long we have been trying to transmit the
message so that the actual time of the message generation can be
determined from receive time (ignoring network delays and only at
accuracy of one second).

For interim updates, only value 0 is used since there are no
retransmissions of the same message. For other accounting messages, the
initial attempt goes out with value 0 and the retransmissions, if
needed, show the number of seconds the message has been waiting in the
queue.

Update the Identifier and Authenticator in the messages whenever
updating the Acct-Delay-Time per RFC 2866, 4.1 requirements.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/ap/accounting.c

@@ -152,6 +152,15 @@ static struct radius_msg * accounting_msg(struct hostapd_data *hapd,
 		goto fail;
 	}
 
+	/*
+	 * Add Acct-Delay-Time with zero value for the first transmission. This
+	 * will be updated within radius_client.c when retransmitting the frame.
+	 */
+	if (!radius_msg_add_attr_int32(msg, RADIUS_ATTR_ACCT_DELAY_TIME, 0)) {
+		wpa_printf(MSG_INFO, "Could not add Acct-Delay-Time");
+		goto fail;
+	}
+
 	return msg;
 
  fail:

src/radius/radius_client.c

@@ -365,6 +365,8 @@ static int radius_client_retransmit(struct radius_client_data *radius,
 	int s;
 	struct wpabuf *buf;
 	size_t prev_num_msgs;
+	u8 *acct_delay_time;
+	size_t acct_delay_time_len;
 
 	if (entry->msg_type == RADIUS_ACCT ||
 	    entry->msg_type == RADIUS_ACCT_INTERIM) {
@@ -418,6 +420,34 @@ static int radius_client_retransmit(struct radius_client_data *radius,
 		return 1;
 	}
 
+	if (entry->msg_type == RADIUS_ACCT &&
+	    radius_msg_get_attr_ptr(entry->msg, RADIUS_ATTR_ACCT_DELAY_TIME,
+				    &acct_delay_time, &acct_delay_time_len,
+				    NULL) == 0 &&
+	    acct_delay_time_len == 4) {
+		struct radius_hdr *hdr;
+		u32 delay_time;
+
+		/*
+		 * Need to assign a new identifier since attribute contents
+		 * changes.
+		 */
+		hdr = radius_msg_get_hdr(entry->msg);
+		hdr->identifier = radius_client_get_id(radius);
+
+		/* Update Acct-Delay-Time to show wait time in queue */
+		delay_time = now - entry->first_try;
+		WPA_PUT_BE32(acct_delay_time, delay_time);
+
+		wpa_printf(MSG_DEBUG,
+			   "RADIUS: Updated Acct-Delay-Time to %u for retransmission",
+			   delay_time);
+		radius_msg_finish_acct(entry->msg, entry->shared_secret,
+				       entry->shared_secret_len);
+		if (radius->conf->msg_dumps)
+			radius_msg_dump(entry->msg);
+	}
+
 	/* retransmit; remove entry if too many attempts */
 	entry->attempts++;
 	hostapd_logger(radius->ctx, entry->addr, HOSTAPD_MODULE_RADIUS,