netdev - Re: [PATCHv3 iproute2-next 3/7] iproute_lwtunnel: add options support for erspan metadata

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Message-ID: <793b8ff4-c04a-f962-f54f-3eae87a42963@gmail.com>
Date:   Sat, 15 Feb 2020 09:51:11 -0700
From:   David Ahern <dsahern@...il.com>
To:     Xin Long <lucien.xin@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Cc:     network dev <netdev@...r.kernel.org>,
        Simon Horman <simon.horman@...ronome.com>
Subject: Re: [PATCHv3 iproute2-next 3/7] iproute_lwtunnel: add options support
 for erspan metadata

On 2/14/20 9:18 PM, Xin Long wrote:
> On Sat, Feb 15, 2020 at 8:21 AM Stephen Hemminger
> <stephen@...workplumber.org> wrote:
>>
>> On Sat, 15 Feb 2020 01:40:27 +0800
>> Xin Long <lucien.xin@...il.com> wrote:
>>
>>> This's not gonna work. as the output will be:
>>> {"ver":"0x2","idx":"0","dir":"0x1","hwid":"0x2"}  (string)
>>> instead of
>>> {"ver":2,"index":0,"dir":1,"hwid":2} (number)
>>
>> JSON is typeless. Lots of values are already printed in hex
> You may mean JSON data itself is typeless.
> But JSON objects are typed when parsing JSON data, which includes
> string, number, array, boolean. So it matters how to define the
> members' 'type' in JSON data.
> 
> For example, in python's 'json' module:
> 
> #!/usr/bin/python2
> import json
> json_data_1 = '{"ver":"0x2","idx":"0","dir":"0x1","hwid":"0x2"}'
> json_data_2 = '{"ver":2,"index":0,"dir":1,"hwid":2}'
> parsed_json_1 = (json.loads(json_data_1))
> parsed_json_2 = (json.loads(json_data_2))
> print type(parsed_json_1["hwid"])
> print type(parsed_json_2["hwid"])
> 
> The output is:
> <type 'unicode'>
> <type 'int'>
> 
> Also, '{"result": true}' is different from '{"result": "true"}' when
> loading it in a 3rd-party lib.
> 
> I think the JSON data coming from iproute2 is designed to be used by
> a 3rd-party lib to parse, not just to show to users. To keep these
> members' original type (numbers) is more appropriate, IMO.
> 

Stephen: why do you think all of the numbers should be in hex?

It seems like consistency with existing output should matter more.
ip/link_gre.c for instance prints index as an int, version as an int,
direction as a string and only hwid in hex.

Xin: any reason you did not follow the output of the existing netdev
based solutions?