selftests/net: calibrate fq_band_pktlimit

This test validates per-band packet limits in FQ. Packets are dropped
rather than enqueued if the limit for their band is reached.

This test is timing sensitive. It queues packets in FQ with a future
delivery time to fill the qdisc.

The test failed in a virtual environment (vng). Increase the delays
to make it more tolerant to environments with timing variance.

Signed-off-by: Willem de Bruijn <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/net/fq_band_pktlimit.sh

···
 # 3. send 20 pkts on band A: verify that  0 are queued, 20 dropped
 # 4. send 20 pkts on band B: verify that 10 are queued, 10 dropped
 #
-# Send packets with a 100ms delay to ensure that previously sent
+# Send packets with a delay to ensure that previously sent
 # packets are still queued when later ones are sent.
 # Use SO_TXTIME for this.
 
···
 ip -6 route add fdaa::/64 dev dummy0
 tc qdisc replace dev dummy0 root handle 1: fq quantum 1514 initial_quantum 1514 limit 10
 
-./cmsg_sender -6 -p u -d 100000 -n 20 fdaa::2 8000
+DELAY=400000
+
+./cmsg_sender -6 -p u -d "${DELAY}" -n 20 fdaa::2 8000
 OUT1="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
 
-./cmsg_sender -6 -p u -d 100000 -n 20 fdaa::2 8000
+./cmsg_sender -6 -p u -d "${DELAY}" -n 20 fdaa::2 8000
 OUT2="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
 
-./cmsg_sender -6 -p u -d 100000 -n 20 -P 7 fdaa::2 8000
+./cmsg_sender -6 -p u -d "${DELAY}" -n 20 -P 7 fdaa::2 8000
 OUT3="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
 
 # Initial stats will report zero sent, as all packets are still
-# queued in FQ. Sleep for the delay period (100ms) and see that
+# queued in FQ. Sleep for at least the delay period and see that
 # twenty are now sent.
-sleep 0.1
+sleep 0.6
 OUT4="$(tc -s qdisc show dev dummy0 | grep '^\ Sent')"
 
 # Log the output after the test