netdev - Re: iproute2 bug in json output for encap

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Message-ID: <65b59170-28c2-2e3b-f435-2bdcc6d7b10c@gmail.com>
Date:   Fri, 14 Apr 2023 18:26:03 +0200
From:   Lars Ekman <uablrek@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: iproute2 bug in json output for encap

Hi again,

Digging a little deeper I see that the double "dst" items will cause
problems with most (all?) json parsers. I intend to use "go" and json
parsing will be parsed to a "map" (hash-table) so duplicate keys will
not work.

https://stackoverflow.com/questions/21832701/does-json-syntax-allow-duplicate-keys-in-an-object

IMHO it would be better to use a structured "encap" item. Something like;

[ {
    "dst": "192.168.11.0/24",
    "encap": {
        "protocol": "ip6",
        "id": 0,
        "src": "::",
        "dst": "fd00::c0a8:2dd",
        "hoplimit": 0,
        "tc": 0
    },
    "scope": "link",
    "flags": [ ]
} ]

Best Regards,

Lars Ekman



On 2023-04-14 18:12, Lars Ekman wrote:
> Hi,
>
> Thanks for the reply. You are right, it is jq that eats one ot the
> double "dst" items.
>
> vm-002 ~ # ip -j -p route show proto 5
> [ {
>         "dst": "192.168.11.0/24",
>         "encap": "ip6",
>         "id": 0,
>         "src": "::",
>         "dst": "fd00::c0a8:2dd",
>         "hoplimit": 0,
>         "tc": 0,
>         "dev": "dummy0",
>         "scope": "link",
>         "flags": [ ]
>     } ]
> vm-002 ~ # ip -j -p route show proto 5 | jq
> [
>   {
>     "dst": "fd00::c0a8:2dd",
>     "encap": "ip6",
>     "id": 0,
>     "src": "::",
>     "hoplimit": 0,
>     "tc": 0,
>     "dev": "dummy0",
>     "scope": "link",
>     "flags": []
>   }
> ]
>
> Sorry for the fuss.
>
> Best Regards,
>
> Lars Ekman
>
>
> And btw I did upgrade *before* posting :-)
>
> vm-002 ~ # ip -V
> ip utility, iproute2-6.2.0, libbpf 1.1.0
> vm-002 ~ # uname -r
> 6.2.7
>
>
>
> On 2023-04-14 17:21, Stephen Hemminger wrote:
>> On Fri, 14 Apr 2023 10:29:15 +0200
>> Lars Ekman <uablrek@...il.com> wrote:
>>
>>> The destination is lost in json printout and replaced by the encap 
>>> destination. The destination can even be ipv6 for an ipv4 route.
>>>
>>> Example:
>>>
>>> vm-002 ~ # ip route add 10.0.0.0/24 proto 5 dev ip6tnl6 encap ip6 dst 
>>> fd00::192.168.2.221
>>> vm-002 ~ # ip route show proto 5
>>> 10.0.0.0/24  encap ip6 id 0 src :: dst fd00::c0a8:2dd hoplimit 0 tc 0 
>>> dev ip6tnl6 scope link
>>> vm-002 ~ # ip -j route show proto 5 | jq
>>> [
>>>    {
>>>      "dst": "fd00::c0a8:2dd",
>>>      "encap": "ip6",
>>>      "id": 0,
>>>      "src": "::",
>>>      "hoplimit": 0,
>>>      "tc": 0,
>>>      "dev": "ip6tnl6",
>>>      "scope": "link",
>>>      "flags": []
>>>    }
>>> ]
>>>
>> Both JSON and regular output show the same address which is coming from
>> the kernel.  I.e not a JSON problem. Also, you don't need to use jq
>> ip has -p flag to pretty print.
>>
>> I can not reproduce this with current kernel and iproute2.
>> # ip route add 192.168.11.0/24 proto 5 dev dummy0 encap ip6 dst fd00::192.168.2.221
>>
>> # ip route show proto 5
>> 192.168.11.0/24  encap ip6 id 0 src :: dst fd00::c0a8:2dd hoplimit 0 tc 0 dev dummy0 scope link 
>>
>> # ip -j -p route show proto 5
>> [ {
>>         "dst": "192.168.11.0/24",
>>         "encap": "ip6",
>>         "id": 0,
>>         "src": "::",
>>         "dst": "fd00::c0a8:2dd",
>>         "hoplimit": 0,
>>         "tc": 0,
>>         "dev": "dummy0",
>>         "scope": "link",
>>         "flags": [ ]
>>     } ]
>>
>>
>> # ip -V
>> ip utility, iproute2-6.1.0, libbpf 1.1.0
>> # uname -r
>> 6.1.0-7-amd64
>>
>>