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Merge branch 'improve-stability-of-big_tcp_tunnels-sh-selftest'

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Alice Mikityanska says:

====================
Improve stability of big_tcp_tunnels.sh selftest

This series addresses flakiness of big_tcp_tunnels.sh discussed at:

https://lore.kernel.org/netdev/349c582c-73e3-468c-91cd-ad6cc3562700@app.fastmail.com/

Lower the thresholds to avoid failures like this (number of packets
below the threshold):

https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/754376/28-big-tcp-tunnels-sh/stdout

Tweak tcp_min_tso_segs and initcwnd to avoid failures like this (BIG TCP
doesn't kick in in slow configurations):

https://netdev-ctrl.bots.linux.dev/logview.html?f=/logs/vmksft/net-dbg/results/751124/21-big-tcp-tunnels-sh/stdout

v2 changes: Use $KSFT_MACHINE_SLOW instead of probing kernel config.

v1: https://lore.kernel.org/netdev/20260814194124.3102581-1-alice.kernel@fastmail.im/
====================

Link: https://patch.msgid.link/20260822120308.1165200-1-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski
2026-08-27 08:42:30 -07:00
parent 6fe7e31a45 1d62b83fb7
commit e2a6641e3b
1 changed files with 34 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
tools/testing/selftests/net/big_tcp_tunnels.sh
View File

@@ -3,6 +3,8 @@
#
# Testing for IPv4 and IPv6 BIG TCP over VXLAN and GENEVE tunnels.
source "$(dirname "$0")/lib.sh"
SERVER_NS=$(mktemp -u server-XXXXXXXX)
SERVER_IP4="192.168.1.1"
SERVER_IP6="2001:db8::1:1"
@@ -15,11 +17,18 @@ CLIENT_IP6="2001:db8::1:2"
CLIENT_IP4_TUN="192.168.2.2"
CLIENT_IP6_TUN="2001:db8::2:2"
: "${PACKETS_THRESHOLD:=1000}"
# Kselftest framework requirement - SKIP code is 4.
ksft_skip=4
if [ -z "$PACKETS_THRESHOLD" ]; then
if [ "$KSFT_MACHINE_SLOW" = yes ]; then
echo 'Debug kernel detected, lowering the default threshold'
PACKETS_THRESHOLD=100
else
PACKETS_THRESHOLD=1000
fi
fi
setup() {
ip netns add "$SERVER_NS"
ip netns add "$CLIENT_NS"
@@ -39,6 +48,9 @@ setup() {
gro_max_size 196608 gro_ipv4_max_size 196608
ip netns exec "$SERVER_NS" netserver >/dev/null
wait_local_port_listen "$SERVER_NS" 12865 tcp
DEFAULT_TCP_MIN_TSO_SEGS=$(ip netns exec "$CLIENT_NS" sysctl -n net.ipv4.tcp_min_tso_segs)
}
setup_tunnel() {
@@ -97,6 +109,8 @@ cleanup() {
}
do_test() {
local packets_threshold="$PACKETS_THRESHOLD"
# When tx csum offload is off, software GSO is performed before passing the
# packet to veth. Check BIG TCP packets inside the VXLAN tunnel to verify
# the software checksum path: if the checksum code is broken, these packets
@@ -115,6 +129,7 @@ do_test() {
else
IPTABLES=ip6tables
fi
packets_threshold=$(( PACKETS_THRESHOLD / 10 ))
fi
if [ "$2" = 4 ]; then
IPTABLES_SACK=iptables
@@ -122,6 +137,21 @@ do_test() {
IPTABLES_SACK=ip6tables
fi
if [ "$3" != 'on' ] && [ "$KSFT_MACHINE_SLOW" = yes ]; then
echo 'Slow configuration; increasing net.ipv4.tcp_min_tso_segs and initcwnd'
ip netns exec "$CLIENT_NS" sysctl -w net.ipv4.tcp_min_tso_segs=52
if [ "$2" = 4 ]; then
ip -netns "$CLIENT_NS" \
route change 192.168.2.0/24 dev tun0 initcwnd 100
else
ip -netns "$CLIENT_NS" -6 \
route change 2001:db8::2:0/112 dev tun0 initcwnd 100
fi
else
ip netns exec "$CLIENT_NS" \
sysctl -w net.ipv4.tcp_min_tso_segs="$DEFAULT_TCP_MIN_TSO_SEGS"
fi
ip netns exec "$SERVER_NS" "$IPTABLES" -w -t raw -I PREROUTING -i "${CAPTURE_IFACE}1" -m length ! --length 0:65535 -m comment --comment "bigtcp"
ip netns exec "$CLIENT_NS" "$IPTABLES" -w -t raw -I OUTPUT -o "${CAPTURE_IFACE}0" -m length ! --length 0:65535 -m comment --comment "bigtcp"
ip netns exec "$SERVER_NS" "$IPTABLES_SACK" -w -t raw -I OUTPUT -o "tun1" -p tcp -m tcp --tcp-flags ACK ACK --tcp-option 5 -m comment --comment "sack"
@@ -147,8 +177,8 @@ do_test() {
echo "Captured BIG TCP RX packets: $PACKETS_SERVER"
echo "Captured BIG TCP TX packets: $PACKETS_CLIENT"
echo "Captured TCP SACK packets: $PACKETS_SACK"
[ "$PACKETS_SERVER" -gt "$PACKETS_THRESHOLD" ] || return 1
[ "$PACKETS_CLIENT" -gt "$PACKETS_THRESHOLD" ] || return 1
[ "$PACKETS_SERVER" -gt "$packets_threshold" ] || return 1
[ "$PACKETS_CLIENT" -gt "$packets_threshold" ] || return 1
[ "$PACKETS_SACK" -lt "$(( PACKETS_CLIENT / 2 ))" ] || return 1
}