[BUG] iproute2 - ip -d -j tuntap outputs malformed JSON

[BUG] iproute2 - ip -d -j tuntap outputs malformed JSON

[Zhengyi Fu]

Hi iproute2 maintainers,

    $ sudo ip -d -j tuntap
    [{"ifname":"tun0","flags":["tun","persist"],"processes":["name":"ssh","pid":86812]}]

The “processes” value looks like it should be an array of objects, so
the inner braces seem to be missing:

    [{"ifname":"tun0","flags":["tun","persist"],"processes":[{"name":"ssh","pid":86812}]}]

Could you confirm whether this is a formatting bug or if the output is
intentionally flattened?

Thanks!

Re: [BUG] iproute2 - ip -d -j tuntap outputs malformed JSON

[Stephen Hemminger]

On Fri, 21 Nov 2025 12:25:41 +0800
Zhengyi Fu <i@fuzy.me> wrote:

> Hi iproute2 maintainers,
> 
>     $ sudo ip -d -j tuntap
>     [{"ifname":"tun0","flags":["tun","persist"],"processes":["name":"ssh","pid":86812]}]
> 
> The “processes” value looks like it should be an array of objects, so
> the inner braces seem to be missing:
> 
>     [{"ifname":"tun0","flags":["tun","persist"],"processes":[{"name":"ssh","pid":86812}]}]
> 
> Could you confirm whether this is a formatting bug or if the output is
> intentionally flattened?
> 
> Thanks!
> 

It should be an array of objects. You can confirm by seeing the output
with multiple processes.

Does this fix it?

diff --git a/ip/iptuntap.c b/ip/iptuntap.c
index b7018a6f..6718ec6c 100644
--- a/ip/iptuntap.c
+++ b/ip/iptuntap.c
@@ -314,6 +314,7 @@ static void show_processes(const char *name)
                                   !strcmp(name, value)) {
                                SPRINT_BUF(pname);
 
+                               open_json_object(NULL);
                                if (get_task_name(pid, pname, sizeof(pname)))
                                        print_string(PRINT_ANY, "name",
                                                     "%s", "<NULL>");
@@ -322,6 +323,7 @@ static void show_processes(const char *name)
                                                     "%s", pname);
 
                                print_uint(PRINT_ANY, "pid", "(%d)", pid);
+                               close_json_object();
                        }
 
                        free(key);

Re: [BUG] iproute2 - ip -d -j tuntap outputs malformed JSON

[Zhengyi Fu]

On 2025-11-22 08:10, Stephen Hemminger wrote:
> On Fri, 21 Nov 2025 12:25:41 +0800
> Zhengyi Fu <i@fuzy.me> wrote:
> 
>> Hi iproute2 maintainers,
>> 
>>     $ sudo ip -d -j tuntap
>>     
>> [{"ifname":"tun0","flags":["tun","persist"],"processes":["name":"ssh","pid":86812]}]
>> 
>> The “processes” value looks like it should be an array of objects, so
>> the inner braces seem to be missing:
>> 
>>     
>> [{"ifname":"tun0","flags":["tun","persist"],"processes":[{"name":"ssh","pid":86812}]}]
>> 
>> Could you confirm whether this is a formatting bug or if the output is
>> intentionally flattened?
>> 
>> Thanks!
>> 
> 
> It should be an array of objects. You can confirm by seeing the output
> with multiple processes.
> 
> Does this fix it?
> 
> diff --git a/ip/iptuntap.c b/ip/iptuntap.c
> index b7018a6f..6718ec6c 100644
> --- a/ip/iptuntap.c
> +++ b/ip/iptuntap.c
> @@ -314,6 +314,7 @@ static void show_processes(const char *name)
>                                    !strcmp(name, value)) {
>                                 SPRINT_BUF(pname);
> 
> +                               open_json_object(NULL);
>                                 if (get_task_name(pid, pname, 
> sizeof(pname)))
>                                         print_string(PRINT_ANY, "name",
>                                                      "%s", "<NULL>");
> @@ -322,6 +323,7 @@ static void show_processes(const char *name)
>                                                      "%s", pname);
> 
>                                 print_uint(PRINT_ANY, "pid", "(%d)", 
> pid);
> +                               close_json_object();
>                         }
> 
>                         free(key);

Yes, it does.  Thanks!