netdev - Re: [PATCH iproute2] ip: do not exit if RTM

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Date:   Tue, 22 Sep 2020 17:16:46 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jan Engelhardt <jengelh@...i.de>,
        Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] ip: do not exit if RTM_GETNSID failed

On 9/22/20 12:28 AM, Jan Engelhardt wrote:
> 
> On Tuesday 2020-09-22 02:22, Stephen Hemminger wrote:
>> Jan Engelhardt <jengelh@...i.de> wrote:
>>
>>> `ip addr` when run under qemu-user-riscv64, fails. This likely is
>>> due to qemu-5.1 not doing translation of RTM_GETNSID calls.
>>>
>>> 2: host0@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
>>>     link/ether 5a:44:da:1a:c4:0b brd ff:ff:ff:ff:ff:ff
>>> request send failed: Operation not supported
>>>
>>> Treat the situation similar to an absence of procfs.
>>>
>>> Signed-off-by: Jan Engelhardt <jengelh@...i.de>
>>
>> Not a good idea to hide a platform bug in ip command.
>> When you do this, you risk creating all sorts of issues for people that
>> run ip commands in container environments where the send is rejected (perhaps by SELinux)
>> and then things go off into a different failure.
> 
> In the very same function you do
> 
>   fd = open("/proc/self/ns/net", O_RDONLY);
> 
> which equally hides a potential platform bug (namely, forgetting to
> mount /proc in a chroot, or in case SELinux was improperly set-up).
> Why is this measured two different ways?
> 
> 

I think checking for EOPNOTSUPP error is more appropriate than ignoring
all errors.