linux-kernel - Re: [PATCH net-next v2 2/2] selftests: net: add test for dst hint mechanism with directed broadcast addresses

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Message-ID: <98b7d1b2-843c-40c6-8918-1af431aedc5f@redhat.com>
Date: Tue, 19 Aug 2025 12:56:58 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Oscar Maes <oscmaes92@...il.com>, netdev@...r.kernel.org
Cc: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
 kuba@...nel.org, horms@...nel.org, shuah@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/2] selftests: net: add test for dst hint
 mechanism with directed broadcast addresses

On 8/14/25 4:03 PM, Oscar Maes wrote:
>  tools/testing/selftests/net/route_hint.sh | 58 +++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100755 tools/testing/selftests/net/route_hint.sh

You must additionally update the net selftest Makefile to include the
new test.

> 
> diff --git a/tools/testing/selftests/net/route_hint.sh b/tools/testing/selftests/net/route_hint.sh
> new file mode 100755
> index 000000000000..fab08d8b742d
> --- /dev/null
> +++ b/tools/testing/selftests/net/route_hint.sh
> @@ -0,0 +1,58 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +
> +# This test ensures directed broadcast routes use dst hint mechanism
> +
> +CLIENT_NS=$(mktemp -u client-XXXXXXXX)
> +CLIENT_IP4="192.168.0.1"
> +
> +SERVER_NS=$(mktemp -u server-XXXXXXXX)
> +SERVER_IP4="192.168.0.2"

> +
> +BROADCAST_ADDRESS="192.168.0.255"
> +
> +setup() {
> +	ip netns add "${CLIENT_NS}"
> +	ip netns add "${SERVER_NS}"

You can/should use setup_ns() from lib.sh to avoid some duplicate code

> +
> +	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}" addr add "${CLIENT_IP4}/24" dev link0
> +
> +	ip -net "${SERVER_NS}" link set link1 up
> +	ip -net "${SERVER_NS}" addr add "${SERVER_IP4}/24" dev link1
> +
> +	ip netns exec "${CLIENT_NS}" ethtool -K link0 tcp-segmentation-offload off
> +	ip netns exec "${SERVER_NS}" sh -c "echo 500000000 > /sys/class/net/link1/gro_flush_timeout"
> +	ip netns exec "${SERVER_NS}" sh -c "echo 1 > /sys/class/net/link1/napi_defer_hard_irqs"
> +	ip netns exec "${SERVER_NS}" ethtool -K link1 generic-receive-offload on
> +}
> +
> +cleanup() {
> +	ip -net "${SERVER_NS}" link del link1
> +	ip netns del "${CLIENT_NS}"
> +	ip netns del "${SERVER_NS}"
> +}
> +
> +directed_bcast_hint_test()
> +{
> +	echo "Testing for directed broadcast route hint"
> +
> +	orig_in_brd=$(ip netns exec "${SERVER_NS}" lnstat -k in_brd -s0 -i1 -c1 | tr -d ' |')

Likely using the '--json' argument and 'jq' will make the parsing more
clear.

> +	ip netns exec "${CLIENT_NS}" mausezahn link0 -a own -b bcast -A "${CLIENT_IP4}" \
> +		-B "${BROADCAST_ADDRESS}" -c1 -t tcp "sp=1-100,dp=1234,s=1,a=0" -p 5 -q

You should check for mausezahn presence and ev. error out with error
code 4 (ksft_skip)

> +	sleep 1
> +	new_in_brd=$(ip netns exec "${SERVER_NS}" lnstat -k in_brd -s0 -i1 -c1 | tr -d ' |')
> +
> +	res=$(echo "${new_in_brd} - ${orig_in_brd}" | bc)
> +
> +	[ "${res}" -lt 100 ]

It would be helpful additionally printing the test result:  '[ ok ]' /
'[fail] expected ... found ...'

/P