[PATCH iproute2] ip-route: fix json formatting for metrics

[Andrea Claudi <aclaudi@redhat.com>]

Setting metrics for routes currently lead to non-parsable
json output. For example:

$ ip link add type dummy
$ ip route add 192.168.2.0 dev dummy0 metric 100 mtu 1000 rto_min 3
$ ip -j route | jq
parse error: ':' not as part of an object at line 1, column 319

Fixing this opening a json object in the metrics array and using
print_string() instead of fprintf().

This is the output for the above commands applying this patch:

$ ip -j route | jq
[
  {
    "dst": "192.168.2.0",
    "dev": "dummy0",
    "scope": "link",
    "metric": 100,
    "flags": [],
    "metrics": [
      {
        "mtu": 1000,
        "rto_min": 3
      }
    ]
  }
]

Fixes: 663c3cb23103f ("iproute: implement JSON and color output")
Fixes: 968272e791710 ("iproute: refactor metrics print")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
---
 ip/iproute.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index 1669e0138259e..2f9b612b0b506 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -578,6 +578,7 @@ static void print_rta_metrics(FILE *fp, const struct rtattr *rta)
 	int i;
 
 	open_json_array(PRINT_JSON, "metrics");
+	open_json_object(NULL);
 
 	parse_rtattr(mxrta, RTAX_MAX, RTA_DATA(rta), RTA_PAYLOAD(rta));
 
@@ -611,7 +612,7 @@ static void print_rta_metrics(FILE *fp, const struct rtattr *rta)
 			print_rtax_features(fp, val);
 			break;
 		default:
-			fprintf(fp, "%u ", val);
+			print_uint(PRINT_ANY, mx_names[i], "%u ", val);
 			break;
 
 		case RTAX_RTT:
@@ -639,6 +640,7 @@ static void print_rta_metrics(FILE *fp, const struct rtattr *rta)
 		}
 	}
 
+	close_json_object();
 	close_json_array(PRINT_JSON, NULL);
 }
 
-- 
2.20.1