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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.
This commit is contained in:
Harald Welte 2013-06-22 09:44:00 +02:00
parent a62fe31d69
commit 27b2bb7e92
1 changed files with 33 additions and 10 deletions
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43
src/gb/gprs_bssgp.c
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@ -590,16 +590,20 @@ static int fc_queue_timer_cfg(struct bssgp_flow_control *fc)
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 @@ int bssgp_fc_ms_init(struct bssgp_flow_control *fc_ms, uint16_t bvci,
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 @@ static int bssgp_rx_fc_bvc(struct msgb *msg, struct tlv_parsed *tp,
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));