1#!/bin/bash 2# SPDX-License-Identifier: GPL-2.0 3# 4# Ensures broadcast route MTU is respected 5 6CLIENT_NS=$(mktemp -u client-XXXXXXXX) 7CLIENT_IP4="192.168.0.1/24" 8CLIENT_BROADCAST_ADDRESS="192.168.0.255" 9 10SERVER_NS=$(mktemp -u server-XXXXXXXX) 11SERVER_IP4="192.168.0.2/24" 12 13setup() { 14 ip netns add "${CLIENT_NS}" 15 ip netns add "${SERVER_NS}" 16 17 ip -net "${SERVER_NS}" link add link1 type veth peer name link0 netns "${CLIENT_NS}" 18 19 ip -net "${CLIENT_NS}" link set link0 up 20 ip -net "${CLIENT_NS}" link set link0 mtu 9000 21 ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}" dev link0 22 23 ip -net "${SERVER_NS}" link set link1 up 24 ip -net "${SERVER_NS}" link set link1 mtu 1500 25 ip -net "${SERVER_NS}" addr add "${SERVER_IP4}" dev link1 26 27 read -r -a CLIENT_BROADCAST_ENTRY <<< "$(ip -net "${CLIENT_NS}" route show table local type broadcast)" 28 ip -net "${CLIENT_NS}" route del "${CLIENT_BROADCAST_ENTRY[@]}" 29 ip -net "${CLIENT_NS}" route add "${CLIENT_BROADCAST_ENTRY[@]}" mtu 1500 30 31 ip net exec "${SERVER_NS}" sysctl -wq net.ipv4.icmp_echo_ignore_broadcasts=0 32} 33 34cleanup() { 35 ip -net "${SERVER_NS}" link del link1 36 ip netns del "${CLIENT_NS}" 37 ip netns del "${SERVER_NS}" 38} 39 40trap cleanup EXIT 41 42setup && 43 echo "Testing for broadcast route MTU" && 44 ip net exec "${CLIENT_NS}" ping -f -M want -q -c 1 -s 8000 -w 1 -b "${CLIENT_BROADCAST_ADDRESS}" > /dev/null 2>&1 45 46exit $? 47 48