BSSGP: prevent divide-by-zero in flow control
If the BTS tells us to not send any data at all anymore (bucket leak
rate of 0 bits per second), then we should respect this and not run into
a divide-by-zero. However, as this indicates complete overload, we
print a log message to that regard.
diff --git a/src/gb/gprs_bssgp.c b/src/gb/gprs_bssgp.c
index e41c7ef..5ef1887 100644
--- a/src/gb/gprs_bssgp.c
+++ b/src/gb/gprs_bssgp.c
@@ -590,16 +590,20 @@
fcqe = llist_entry(&fc->queue.next, struct bssgp_fc_queue_element,
list);
- /* Calculate the point in time at which we will have leaked
- * a sufficient number of bytes from the bucket to transmit
- * the first PDU in the queue */
- msecs = (fcqe->llc_pdu_len * 1000) / fc->bucket_leak_rate;
- /* FIXME: add that time to fc->time_last_pdu and subtract it from
- * current time */
-
- fc->timer.data = fc;
- fc->timer.cb = &fc_timer_cb;
- osmo_timer_schedule(&fc->timer, msecs / 1000, (msecs % 1000) * 1000);
+ if (fc->bucket_leak_rate != 0) {
+ /* Calculate the point in time at which we will have leaked
+ * a sufficient number of bytes from the bucket to transmit
+ * the first PDU in the queue */
+ msecs = (fcqe->llc_pdu_len * 1000) / fc->bucket_leak_rate;
+ /* FIXME: add that time to fc->time_last_pdu and subtract it from
+ * current time */
+ fc->timer.data = fc;
+ fc->timer.cb = &fc_timer_cb;
+ osmo_timer_schedule(&fc->timer, msecs / 1000, (msecs % 1000) * 1000);
+ } else {
+ /* If the PCU is telling us to not send any more data at all,
+ * there's no point starting a timer. */
+ }
return 0;
}
@@ -742,6 +746,8 @@
static int bssgp_rx_fc_bvc(struct msgb *msg, struct tlv_parsed *tp,
struct bssgp_bvc_ctx *bctx)
{
+ uint32_t old_leak_rate = bctx->fc->bucket_leak_rate;
+ uint32_t old_r_def_ms = bctx->r_default_ms;
DEBUGP(DBSSGP, "BSSGP BVCI=%u Rx Flow Control BVC\n",
bctx->bvci);
@@ -769,6 +775,23 @@
bctx->r_default_ms = 100 *
ntohs(*(uint16_t *)TLVP_VAL(tp, BSSGP_IE_R_DEFAULT_MS)) / 8;
+ if (old_leak_rate != 0 && bctx->fc->bucket_leak_rate == 0)
+ LOGP(DBSSGP, LOGL_NOTICE, "BSS instructs us to bucket leak "
+ "rate of 0, stopping all DL GPRS!\n");
+ else if (old_leak_rate == 0 && bctx->fc->bucket_leak_rate != 0)
+ LOGP(DBSSGP, LOGL_NOTICE, "BSS instructs us to bucket leak "
+ "rate of != 0, restarting all DL GPRS!\n");
+
+ if (old_r_def_ms != 0 && bctx->r_default_ms == 0)
+ LOGP(DBSSGP, LOGL_NOTICE, "BSS instructs us to MS default "
+ "bucket leak rate of 0, stopping DL GPRS!\n");
+ else if (old_r_def_ms == 0 && bctx->r_default_ms != 0)
+ LOGP(DBSSGP, LOGL_NOTICE, "BSS instructs us to MS default "
+ "bucket leak rate != 0, restarting DL GPRS!\n");
+
+ /* reconfigure the timer for flow control based on new values */
+ fc_queue_timer_cfg(bctx->fc);
+
/* Send FLOW_CONTROL_BVC_ACK */
return bssgp_tx_fc_bvc_ack(msgb_nsei(msg), *TLVP_VAL(tp, BSSGP_IE_TAG),
msgb_bvci(msg));