meter: fix excess token bucket update in srtcm

As per srTCM RFC 2697, we should be updating the E bucket only after the
C bucket overflows. This patch fixes the current DPDK implementation,
where we are updating both the buckets simultaneously at the same rate
(CIR) which results in token accumulation rate of (2*CIR).

Signed-off-by: Nikhil Jagtap <nikhil.jagtap@gmail.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>

diff --git a/lib/librte_meter/rte_meter.h b/lib/librte_meter/rte_meter.h
index 2cd8d81..2ab7184 100644 (file)
--- a/lib/librte_meter/rte_meter.h
+++ b/lib/librte_meter/rte_meter.h
@@ -232,13 +232,15 @@ rte_meter_srtcm_color_blind_check(struct rte_meter_srtcm *m,
        n_periods = time_diff / m->cir_period;
        m->time += n_periods * m->cir_period;
 
+       /* Put the tokens overflowing from tc into te bucket */
        tc = m->tc + n_periods * m->cir_bytes_per_period;
-       if (tc > m->cbs)
+       te = m->te;
+       if (tc > m->cbs) {
+               te += (tc - m->cbs);
+               if (te > m->ebs)
+                       te = m->ebs;
                tc = m->cbs;
-
-       te = m->te + n_periods * m->cir_bytes_per_period;
-       if (te > m->ebs)
-               te = m->ebs;
+       }
 
        /* Color logic */
        if (tc >= pkt_len) {
@@ -271,13 +273,15 @@ rte_meter_srtcm_color_aware_check(struct rte_meter_srtcm *m,
        n_periods = time_diff / m->cir_period;
        m->time += n_periods * m->cir_period;
 
+       /* Put the tokens overflowing from tc into te bucket */
        tc = m->tc + n_periods * m->cir_bytes_per_period;
-       if (tc > m->cbs)
+       te = m->te;
+       if (tc > m->cbs) {
+               te += (tc - m->cbs);
+               if (te > m->ebs)
+                       te = m->ebs;
                tc = m->cbs;
-
-       te = m->te + n_periods * m->cir_bytes_per_period;
-       if (te > m->ebs)
-               te = m->ebs;
+       }
 
        /* Color logic */
        if ((pkt_color == e_RTE_METER_GREEN) && (tc >= pkt_len)) {