selftests: mptcp: simult_flows: disable GSO

Netem is used to apply a rate limit, and its 'limit' option is per
packet.

Disable GSO on both sides to work with packets of a specific size. That
increases the number of packets, but stabilise the throughput. As a
consequence, limits are more adapted, and the bufferbloat is reduced.

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-v1-1-9afc4e742090@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 d11a8b949aab5c03a85aa898d5a296e3bfe75003..345cf200c653f2612d4b6ed3c15a98e72d6ffadc 100755 (executable)
--- a/tools/testing/selftests/net/mptcp/simult_flows.sh
+++ b/tools/testing/selftests/net/mptcp/simult_flows.sh
@@ -76,13 +76,13 @@ setup()
 
        ip -net "$ns1" addr add 10.0.1.1/24 dev ns1eth1
        ip -net "$ns1" addr add dead:beef:1::1/64 dev ns1eth1 nodad
-       ip -net "$ns1" link set ns1eth1 up mtu 1500
+       ip -net "$ns1" link set ns1eth1 up mtu 1500 gso_max_segs 0
        ip -net "$ns1" route add default via 10.0.1.2
        ip -net "$ns1" route add default via dead:beef:1::2
 
        ip -net "$ns1" addr add 10.0.2.1/24 dev ns1eth2
        ip -net "$ns1" addr add dead:beef:2::1/64 dev ns1eth2 nodad
-       ip -net "$ns1" link set ns1eth2 up mtu 1500
+       ip -net "$ns1" link set ns1eth2 up mtu 1500 gso_max_segs 0
        ip -net "$ns1" route add default via 10.0.2.2 metric 101
        ip -net "$ns1" route add default via dead:beef:2::2 metric 101
 
@@ -91,21 +91,21 @@ setup()
 
        ip -net "$ns2" addr add 10.0.1.2/24 dev ns2eth1
        ip -net "$ns2" addr add dead:beef:1::2/64 dev ns2eth1 nodad
-       ip -net "$ns2" link set ns2eth1 up mtu 1500
+       ip -net "$ns2" link set ns2eth1 up mtu 1500 gso_max_segs 0
 
        ip -net "$ns2" addr add 10.0.2.2/24 dev ns2eth2
        ip -net "$ns2" addr add dead:beef:2::2/64 dev ns2eth2 nodad
-       ip -net "$ns2" link set ns2eth2 up mtu 1500
+       ip -net "$ns2" link set ns2eth2 up mtu 1500 gso_max_segs 0
 
        ip -net "$ns2" addr add 10.0.3.2/24 dev ns2eth3
        ip -net "$ns2" addr add dead:beef:3::2/64 dev ns2eth3 nodad
-       ip -net "$ns2" link set ns2eth3 up mtu 1500
+       ip -net "$ns2" link set ns2eth3 up mtu 1500 gso_max_segs 0
        ip netns exec "$ns2" sysctl -q net.ipv4.ip_forward=1
        ip netns exec "$ns2" sysctl -q net.ipv6.conf.all.forwarding=1
 
        ip -net "$ns3" addr add 10.0.3.3/24 dev ns3eth1
        ip -net "$ns3" addr add dead:beef:3::3/64 dev ns3eth1 nodad
-       ip -net "$ns3" link set ns3eth1 up mtu 1500
+       ip -net "$ns3" link set ns3eth1 up mtu 1500 gso_max_segs 0
        ip -net "$ns3" route add default via 10.0.3.2
        ip -net "$ns3" route add default via dead:beef:3::2