Commit 5777d187 authored by Oscar Maes's avatar Oscar Maes Committed by Jakub Kicinski
Browse files

selftests: net: add test for variable PMTU in broadcast routes 



Added a test for variable PMTU in broadcast routes.

This test uses iputils' ping and attempts to send a ping between
two peers, which should result in a regular echo reply.

This test will fail when the receiving peer does not receive the echo
request due to a lack of packet fragmentation.

Signed-off-by: default avatarOscar Maes <oscmaes92@gmail.com>
Link: https://patch.msgid.link/20250710142714.12986-2-oscmaes92@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 9e30ecf2

tools/testing/selftests/net/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ TEST_PROGS += skf_net_off.sh 
TEST_GEN_FILES += skf_net_off

TEST_GEN_FILES += tfo

TEST_PROGS += tfo_passive.sh

TEST_PROGS += broadcast_pmtu.sh



# YNL files, must be before "include ..lib.mk"

YNL_GEN_FILES := busy_poller netlink-dumps

tools/testing/selftests/net/broadcast_pmtu.sh

0 → 100755
+47 −0
Original line number Diff line number Diff line 
#!/bin/bash

# SPDX-License-Identifier: GPL-2.0

#

# Ensures broadcast route MTU is respected



CLIENT_NS=$(mktemp -u client-XXXXXXXX)

CLIENT_IP4="192.168.0.1/24"

CLIENT_BROADCAST_ADDRESS="192.168.0.255"



SERVER_NS=$(mktemp -u server-XXXXXXXX)

SERVER_IP4="192.168.0.2/24"



setup() {

	ip netns add "${CLIENT_NS}"

	ip netns add "${SERVER_NS}"



	ip -net "${SERVER_NS}" link add link1 type veth peer name link0 netns "${CLIENT_NS}"



	ip -net "${CLIENT_NS}" link set link0 up

	ip -net "${CLIENT_NS}" link set link0 mtu 9000

	ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}" dev link0



	ip -net "${SERVER_NS}" link set link1 up

	ip -net "${SERVER_NS}" link set link1 mtu 1500

	ip -net "${SERVER_NS}" addr add "${SERVER_IP4}" dev link1



	read -r -a CLIENT_BROADCAST_ENTRY <<< "$(ip -net "${CLIENT_NS}" route show table local type broadcast)"

	ip -net "${CLIENT_NS}" route del "${CLIENT_BROADCAST_ENTRY[@]}"

	ip -net "${CLIENT_NS}" route add "${CLIENT_BROADCAST_ENTRY[@]}" mtu 1500



	ip net exec "${SERVER_NS}" sysctl -wq net.ipv4.icmp_echo_ignore_broadcasts=0

}



cleanup() {

	ip -net "${SERVER_NS}" link del link1

	ip netns del "${CLIENT_NS}"

	ip netns del "${SERVER_NS}"

}



trap cleanup EXIT



setup &&

	echo "Testing for broadcast route MTU" &&

	ip net exec "${CLIENT_NS}" ping -f -M want -q -c 1 -s 8000 -w 1 -b "${CLIENT_BROADCAST_ADDRESS}" > /dev/null 2>&1



exit $?