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Thu, 03 Jul 2025 08:30:20 -0700 (PDT) From: Oscar Maes To: netdev@vger.kernel.org Cc: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, Oscar Maes Subject: [PATCH net v2 2/2] selftests: net: add test for variable PMTU in broadcast routes Date: Thu, 3 Jul 2025 17:28:38 +0200 Message-Id: <20250703152838.2993-2-oscmaes92@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250703152838.2993-1-oscmaes92@gmail.com> References: <20250703152838.2993-1-oscmaes92@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: Oscar Maes --- tools/testing/selftests/net/Makefile | 1 + tools/testing/selftests/net/broadcast_pmtu.sh | 47 +++++++++++++++++++ 2 files changed, 48 insertions(+) create mode 100755 tools/testing/selftests/net/broadcast_pmtu.sh diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile index 332f38761..f4aa94588 100644 --- a/tools/testing/selftests/net/Makefile +++ b/tools/testing/selftests/net/Makefile @@ -112,6 +112,7 @@ 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 diff --git a/tools/testing/selftests/net/broadcast_pmtu.sh b/tools/testing/selftests/net/broadcast_pmtu.sh new file mode 100755 index 000000000..726eb5d25 --- /dev/null +++ b/tools/testing/selftests/net/broadcast_pmtu.sh @@ -0,0 +1,47 @@ +#!/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 $? + -- 2.39.5