linux-kernel - Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL] in vrf "bind

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Date:   Fri, 2 Jun 2023 14:35:20 +0200
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Guillaume Nault <gnault@...hat.com>
Cc:     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>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL] in vrf "bind -
 ns-B IPv6 LLA" test

On 5/31/23 20:11, Guillaume Nault wrote:
> On Wed, May 24, 2023 at 02:17:09PM +0200, Mirsad Todorovac wrote:
>> Hi,
> 
> Hi Mirsad,

Hi Guillaume,

>> The very recent 6.4-rc3 kernel build with AlmaLinux 8.7 on LENOVO 10TX000VCR
>> desktop box fails one test:
>>
>> [root@...t net]# ./fcnal-test.sh
>> [...]
>> TEST: ping out, vrf device+address bind - ns-B loopback IPv6                  [ OK ]
>> TEST: ping out, vrf device+address bind - ns-B IPv6 LLA                       [FAIL]
>> TEST: ping in - ns-A IPv6                                                     [ OK ]
>> [...]
>> Tests passed: 887
>> Tests failed:   1
>> [root@...t net]#
> 
> This test also fails on -net. The problem is specific to ping sockets
> (same test passes with raw sockets). I believe this test has always
> failed since fcnal-test.sh started using net.ipv4.ping_group_range
> (commit e71b7f1f44d3 ("selftests: add ping test with ping_group_range
> tuned")).
> 
> The executed command is:
> 
> ip netns exec ns-A ip vrf exec red /usr/bin/ping6 -c1 -w1 -I 2001:db8:3::1 fe80::a846:b5ff:fe4c:da4e%eth1
> 
> So ping6 is executed inside VRF 'red' and sets .sin6_scope_id to 'eth1'
> (which is a slave device of VRF 'red'). Therefore, we have
> sk->sk_bound_dev_if == 'red' and .sin6_scope_id == 'eth1'. This fails
> because ping_v6_sendmsg() expects them to be equal:
> 
> static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> {
> ...
>                  if (__ipv6_addr_needs_scope_id(ipv6_addr_type(daddr)))
>                          oif = u->sin6_scope_id;
> ...
>          if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
>              (addr_type & IPV6_ADDR_MAPPED) ||
>              (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if)) <-- oif='eth1', but ->sk_bound_dev_if='red'
>                  return -EINVAL;
> ...
> }

Thank you for your thorough investigation. It helps a great deal to
understand the issue.

I am really not that into the network stack, though I can always smuggle
the work on the network stack as a work on high-bandwidth multimedia
and do it in day hours.

Probably I need to catch up with the network stack homework.

> I believe this condition should be relaxed to allow the case where
> ->sk_bound_dev_if is oif's master device (and maybe there are other
> VRF cases to also consider).

I have looked into the code, but currently my knowledge of the code is
not sufficient for the intervention.

Thank you,
Mirsad