netdev - Re: [RFC PATCH net-next 3/3] net: dsa: never skip VLAN configuration

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Date:   Wed, 6 Jul 2022 21:57:40 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Petr Machata <petrm@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Hauke Mehrtens <hauke@...ke-m.de>
Subject: Re: [RFC PATCH net-next 3/3] net: dsa: never skip VLAN configuration

Hi Vladimir,

On Wed, Jul 6, 2022 at 6:45 PM Vladimir Oltean <vladimir.oltean@....com> wrote:
[...]
> Somehow we should do something to make sure that the OpenWRT devices are
> able to run the selftests, because there's a large number of DSA switches
> intended for that segment and we should all be onboard (easily).
I could work on this on the OpenWrt side.
But this would require me to get any test working at all...

I am struggling with not seeing any ping responses.
Instead of adding VLANs and others to the mix I started with seemingly
simple commands while connecting an Ethernet cable between lan1 and
lan2 and another cable between lan3 and lan4:
1) give each port a unique MAC address, which is not the default on my
device under test
ip link set dev lan1 address 6a:88:f1:99:e1:81
ip link set dev lan2 address 6a:88:f1:99:e1:82
ip link set dev lan3 address 6a:88:f1:99:e1:83
ip link set dev lan4 address 6a:88:f1:99:e1:84

2) set up IP addresses on LAN1 and LAN2
ip addr add 192.168.2.1/24 brd + dev lan1
ip addr add 192.168.2.2/24 brd + dev lan2

3) bring up the interfaces
ip link set up dev lan1
ip link set up dev lan2

4) start tcpdump on LAN1
tcpdump -i lan1 &

5) start ping from LAN2 to LAN1
ping -I lan2 192.168.2.1

result:
PING 192.168.2.1 (192.168.2.1): 56 data bytes
20:02:01.522977 ARP, Request who-has 192.168.2.1 tell 192.168.2.2, length 46
20:02:02.569234 ARP, Request who-has 192.168.2.1 tell 192.168.2.2, length 46
20:02:03.609132 ARP, Request who-has 192.168.2.1 tell 192.168.2.2, length 46
20:02:05.524200 ARP, Request who-has 192.168.2.1 tell 192.168.2.2, length 46
20:02:06.569226 ARP, Request who-has 192.168.2.1 tell 192.168.2.2, length 46
...repeats...

So LAN1 can see the ARP request from the ping on LAN2.
But I am not seeing Linux trying to send a reply.

I already verified that nftables doesn't have any rules active (if it
was I think it would rather result in tcpdump not seeing the who-has
request):
# nft list tables
#

# grep "" /proc/sys/net/ipv4/icmp_echo_ignore_*
/proc/sys/net/ipv4/icmp_echo_ignore_all:0
/proc/sys/net/ipv4/icmp_echo_ignore_broadcasts:1

# ps | grep netif
3014 root      1308 S    grep netif
#

To make things worse: if I let OpenWrt's netifd configure LAN1 and
LAN2 as single ports with above IP addresses ping works.
Something is odd and I am not sure how to find out what's wrong.

> I wonder, would it be possible to set up a debian chroot?
I'm thinking of packaging the selftests as OpenWrt package and also
providing all needed dependencies as OpenWrt packages.
I think (or I hope, not sure yet) the ping interval is just a matter
of a busybox config option.


Best regards,
Martin