[PATCH iproute2-net v2] mptcp: limits: fix JSON support

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

print_mptcp_limit() was trying to open a JSON sub-object and closing it,
but no JSON object was actually created before.

Because of that, JSON support was not working with the MPTCP limits:

  $ ip -j -p mptcp limits show
  add_addr_accepted 0 subflows 2

Create a "plain" object before calling print_mptcp_limit: the MPTCP
limits are different from what is usually seen in IP commands. Indeed,
this object doesn't list multiple items with different attributes, but
only a bunch of attributes. With this _plain() helpers, an extra array
is not going to be added: it is not needed and doesn't make sense here.

After this modification, we now have:

  $ ip -j -p mptcp limits show
  {
      "add_addr_accepted": 0,
      "subflows": 2
  }

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Changes in v2:
- Explain why _plain() is used here. (Stephen's LLM review)
- Add missing 'not' in the commit message. (Stephen's LLM review)
- (No code change.)
- Link to v1: https://patch.msgid.link/20261029-mptcp-limits-json-v1-1-7ac73cdab054@kernel.org
---
 ip/ipmptcp.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ip/ipmptcp.c b/ip/ipmptcp.c
index 02cf72ce..54976c08 100644
--- a/ip/ipmptcp.c
+++ b/ip/ipmptcp.c
@@ -446,7 +446,14 @@ static int mptcp_limit_get_set(int argc, char **argv, int cmd)
 
 	ret = 0;
 	if (do_get) {
+		/* This object is different from what is usually seen in IP
+		 * commands: it doesn't list multiple items with different
+		 * attributes, but only a bunch of attributes. Use _plain()
+		 * because an array is not needed and doesn't make sense here.
+		 */
+		new_json_obj_plain(json);
 		ret = print_mptcp_limit(answer, stdout);
+		delete_json_obj_plain();
 		free(answer);
 	}
 

---
base-commit: d95f66508b32fb2c51e70a9127dffd1db8623614
change-id: 20261029-mptcp-limits-json-f60c82b687fa

Best regards,
--  
Matthieu Baerts (NGI0) <matttbe@kernel.org>