selftests: mptcp: simult_flows: adapt limits

Avoid using a fixed limit, no matter the setup. This was causing too
high bufferbloat in some situations, e.g. with a low bandwidth and very
low delay because the default limit was too high for this case.

Instead, use more appropriated limits. Note that unbalanced bandwidth
modes seem to require slightly higher limits to cope with the different
bursts.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260527-net-mptcp-sft-bufferbloat-exit-v1-2-9afc4e742090@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/mptcp/simult_flows.sh b/tools/testing/selftests/net/mptcp/simult_flows.sh
index 345cf200c653f2612d4b6ed3c15a98e72d6ffadc..7b9aabe1017041b14a1e3badf70d438008274b94 100755 (executable)
--- a/tools/testing/selftests/net/mptcp/simult_flows.sh
+++ b/tools/testing/selftests/net/mptcp/simult_flows.sh
@@ -223,9 +223,11 @@ run_test()
        local rate2=$2
        local delay1=$3
        local delay2=$4
+       local limit1=$5
+       local limit2=$6
        local lret
        local dev
-       shift 4
+       shift 6
        local msg=$*
 
        [ $delay1 -gt 0 ] && delay1="delay ${delay1}ms" || delay1=""
@@ -240,10 +242,10 @@ run_test()
 
        # keep the queued pkts number low, or the RTT estimator will see
        # increasing latency over time.
-       tc -n $ns1 qdisc add dev ns1eth1 root netem rate ${rate1}mbit $delay1 limit 50
-       tc -n $ns1 qdisc add dev ns1eth2 root netem rate ${rate2}mbit $delay2 limit 50
-       tc -n $ns2 qdisc add dev ns2eth1 root netem rate ${rate1}mbit $delay1 limit 50
-       tc -n $ns2 qdisc add dev ns2eth2 root netem rate ${rate2}mbit $delay2 limit 50
+       tc -n $ns1 qdisc add dev ns1eth1 root netem rate ${rate1}mbit $delay1 limit ${limit1}
+       tc -n $ns1 qdisc add dev ns1eth2 root netem rate ${rate2}mbit $delay2 limit ${limit2}
+       tc -n $ns2 qdisc add dev ns2eth1 root netem rate ${rate1}mbit $delay1 limit ${limit1}
+       tc -n $ns2 qdisc add dev ns2eth2 root netem rate ${rate2}mbit $delay2 limit ${limit2}
 
        # time is measured in ms, account for transfer size, aggregated link speed
        # and header overhead (10%)
@@ -301,13 +303,13 @@ done
 
 setup
 mptcp_lib_subtests_last_ts_reset
-run_test 10 10 0 0 "balanced bwidth"
-run_test 10 10 1 25 "balanced bwidth with unbalanced delay"
+run_test 10 10 0 0  20 20 "balanced bwidth"
+run_test 10 10 1 25 20 50 "balanced bwidth with unbalanced delay"
 
 # we still need some additional infrastructure to pass the following test-cases
-MPTCP_LIB_SUBTEST_FLAKY=1 run_test 10 3 0 0 "unbalanced bwidth"
-run_test 10 3 1 25 "unbalanced bwidth with unbalanced delay"
-run_test 10 3 25 1 "unbalanced bwidth with opposed, unbalanced delay"
+MPTCP_LIB_SUBTEST_FLAKY=1 run_test 10 3 0 0  30 20 "unbalanced bwidth"
+run_test 10 3 1 25 40 30 "unbalanced bwidth with unbalanced delay"
+run_test 10 3 25 1 50 30 "unbalanced bwidth with opposed, unbalanced delay"
 
 mptcp_lib_result_print_all_tap
 exit $ret