netdev - Re: How to display IPv4 array?

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Date: Tue, 12 Mar 2024 13:48:10 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>, netdev@...r.kernel.org
Subject: Re: How to display IPv4 array?

Tue, Mar 12, 2024 at 01:37:01PM CET, liuhangbin@...il.com wrote:
>Hi Jiri,
>On Tue, Mar 12, 2024 at 01:12:30PM +0100, Jiri Pirko wrote:
>> Tue, Mar 12, 2024 at 11:08:33AM CET, liuhangbin@...il.com wrote:
>> >Hi Jakub,
>> >
>> >I plan to add bond support for Documentation/netlink/specs/rt_link.yaml. While
>> >dealing with the attrs. I got a problem about how to show the bonding arp/ns
>> >targets. Because the arp/ns targets are filled as an array[1]. I tried
>> >something like:
>> >
>> >  -
>> >    name: linkinfo-bond-attrs
>> >    name-prefix: ifla-bond-
>> >    attributes:
>> >      -
>> >        name: arp-ip-target
>> >        type: nest
>> >        nested-attributes: ipv4-addr
>> >  -
>> >    name: ipv4-addr
>> >    attributes:
>> >      -
>> >        name: addr
>> >        type: binary
>> >        display-hint: ipv4
>> >
>> >But this failed with error: Exception: Space 'ipv4-addr' has no attribute with value '0'
>> >Do you have any suggestion?
>> >
>> >[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/drivers/net/bonding/bond_netlink.c#n670
>> 
>> Yeah, that's odd use of attr type, here it is an array index. I'm pretty
>> sure I saw this in the past on different netlink places.
>> I believe that is not supported with the existing ynl code.
>> 
>> Perhaps something like the following might work:
>>       -
>>         name: arp-ip-target
>>         type: binary
>>         display-hint: ipv4
>> 	nested-array: true
>> 
>> "nested-array" would tell the parser to expect a nest that has attr
>> type of value of array index, "type" is the same for all array members.
>> The output will be the same as in case of "multi-attr", array index
>> ignored (I don't see what it would be good for to the user).
>
>Yes, this looks a do-able way. Although we already have a similar type
>'array-nest'...

That is something else. That is you have a nested attribute that holds
multiple nests of the same attr type with attributes inside. Something
completely different from what I see...


>
>I also figured out a workaround. e.g.
>
>  -
>    name: linkinfo-bond-attrs
>    name-prefix: ifla-bond-
>    attributes:
>      -
>        name: arp-ip-target
>        type: nest
>        nested-attributes: ipv4-addr
>
>  -
>    name: ipv4-addr
>    attributes:
>      -
>        name: addr0
>        value: 0
>        type: u32
>        byte-order: big-endian
>        display-hint: ipv4
>      -
>        name: addr1
>        value: 1
>        type: u32
>        byte-order: big-endian
>        display-hint: ipv4

Or, special value "any" or "all" that would match them all?


>
>With this we can show the target like:
>
>     'arp-ip-target': {'addr0': '192.168.1.1',
>                       'addr1': '192.168.1.2'},
>
>But we need to add all BOND_MAX_ARP_TARGETS attrs. Which doesn't like a good
>way. So maybe as you suggested, add a new type "nested-array".



>
>Thanks
>Hangbin