From: Julien Fortin <jul...@cumulusnetworks.com>

This patch converts all output (mostly fprintfs) to the new ip_print api
which handle both regular and json output.
Initialize a json_writer and open an array object if -json was specified.
Note that the JSON attribute naming follows the NETLINK_ATTRIBUTE naming.

In many places throughout the code, IP, matches integer values with
hardcoded strings tables, such as link mode, link operstate or link
family.
In JSON context, this will result in a named string field. In the
very unlikely event that the requested index is out of bound, IP
displays the raw integer value. For JSON context this result in
having a different integer field example bellow:

if (mode >= ARRAY_SIZE(link_modes))
        print_int(PRINT_ANY, "linkmode_index", "mode %d ", mode);
else
        print_string(PRINT_ANY, "linkmode", "mode %s ",
                     link_modes[mode]);

The "_index" suffix is open to discussion and it is something that I came
up with. The bottom line is that you can't have a string field that may
become an int field in specific cases. Programs written in strongly type
languages (like C) might break if they are expecting a string value and
got an integer instead. We don't want to confuse anybody or make the code
even more complicated handling these specifics cases.
Hence the extra "_index" field that is easy to check for and deal with.

JSON schema, followed by live example:

Live config used:
$ ip link add dev vxlan42 type vxlan id 42
$ ip link add dev bond0 type bond
$ ip link add name swp1.50 link swp1 type vlan id 50
$ ip link add dev br0 type bridge
$ ip link set dev vxlan42 master br0
$ ip link set dev bond0 master br0
$ ip link set dev swp1.50 master br0
$ ip link set dev br0 up

$ ip -d link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode
DEFAULT group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0
addrgenmode eui64
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:db:31:88 brd ff:ff:ff:ff:ff:ff promiscuity 0
addrgenmode eui64
3: swp1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode
DEFAULT group default qlen 1000
    link/ether 08:00:27:5b:b1:75 brd ff:ff:ff:ff:ff:ff promiscuity 0
addrgenmode eui64
10: vxlan42: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master br0 state
DOWN mode DEFAULT group default
    link/ether 4a:d9:91:42:a2:d2 brd ff:ff:ff:ff:ff:ff promiscuity 1
    vxlan id 42 srcport 0 0 dstport 8472 ageing 300
    bridge_slave state disabled priority 8 cost 100 hairpin off guard off
root_block off fastleave off learning on flood on port_id 0x8001 port_no
0x1 designated_port 32769 designated_cost 0 designated_bridge
8000.8:0:27:5b:b1:75 designated_root 8000.8:0:27:5b:b1:75 hold_timer
0.00 message_age_timer    0.00 forward_delay_timer    0.00
topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off
mcast_router 1 mcast_fast_leave off mcast_flood on neigh_suppress off
addrgenmode eui64
11: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop master br0
state DOWN mode DEFAULT group default
    link/ether e2:aa:7b:17:c5:14 brd ff:ff:ff:ff:ff:ff promiscuity 1
    bond mode 802.3ad miimon 100 updelay 0 downdelay 0 use_carrier 1
arp_interval 0 arp_validate none arp_all_targets any primary_reselect
always fail_over_mac none xmit_hash_policy layer3+4 resend_igmp 1
num_grat_arp 1 all_slaves_active 0 min_links 1 lp_interval 1
packets_per_slave 1 lacp_rate fast ad_select stable ad_actor_sys_prio
65535 ad_user_port_key 0 ad_actor_system 00:00:00:00:00:00
    bridge_slave state disabled priority 8 cost 100 hairpin off guard off
root_block off fastleave off learning on flood on port_id 0x8002 port_no
0x2 designated_port 32770 designated_cost 0 designated_bridge
8000.8:0:27:5b:b1:75 designated_root 8000.8:0:27:5b:b1:75 hold_timer
0.00 message_age_timer    0.00 forward_delay_timer    0.00
topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off
mcast_router 1 mcast_fast_leave off mcast_flood on neigh_suppress off
addrgenmode eui64
12: swp1.50@swp1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop master
br0 state DOWN mode DEFAULT group default
    link/ether 08:00:27:5b:b1:75 brd ff:ff:ff:ff:ff:ff promiscuity 1
    vlan protocol 802.1Q id 50 <REORDER_HDR>
    bridge_slave state disabled priority 8 cost 100 hairpin off guard off
root_block off fastleave off learning on flood on port_id 0x8003 port_no
0x3 designated_port 32771 designated_cost 0 designated_bridge
8000.8:0:27:5b:b1:75 designated_root 8000.8:0:27:5b:b1:75 hold_timer
0.00 message_age_timer    0.00 forward_delay_timer    0.00
topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off
mcast_router 1 mcast_fast_leave off mcast_flood on neigh_suppress off
addrgenmode eui64
13: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state
DOWN mode DEFAULT group default
    link/ether 08:00:27:5b:b1:75 brd ff:ff:ff:ff:ff:ff promiscuity 0
    bridge forward_delay 1500 hello_time 200 max_age 2000 ageing_time
30000 stp_state 0 priority 32768 vlan_filtering 0 vlan_protocol 802.1Q
bridge_id 8000.8:0:27:5b:b1:75 designated_root 8000.8:0:27:5b:b1:75
root_port 0 root_path_cost 0 topology_change 0 topology_change_detected 0
hello_timer    0.00 tcn_timer    0.00 topology_change_timer    0.00
gc_timer  244.44 vlan_default_pvid 1 vlan_stats_enabled 0 group_fwd_mask 0
group_address 01:80:c2:00:00:00 mcast_snooping 1 mcast_router 1
mcast_query_use_ifaddr 0 mcast_querier 0 mcast_hash_elasticity 4096
mcast_hash_max 4096 mcast_last_member_count 2 mcast_startup_query_count 2
mcast_last_member_interval 100 mcast_membership_interval 26000
mcast_querier_interval 25500 mcast_query_interval 12500
mcast_query_response_interval 1000 mcast_startup_query_interval 3125
mcast_stats_enabled 0 mcast_igmp_version 2 mcast_mld_version 1
nf_call_iptables 0 nf_call_ip6tables 0 nf_call_arptables 0 addrgenmode
eui64

// Schema for: ip -brief link show
[
    {
        "deleted": {
            "type": "bool",
            "attr": "RTM_DELLINK"
        },
        "link": {
            "type": "string",
            "attr": "IFLA_LINK"
        },
        "ifname": {
            "type": "string",
            "attr": "IFNAME"
        },
        "operstate": {
            "type": "string",
            "attr": "IFLA_OPERSTATE",
            "mutually_exclusive": {
                "operstate_index": {
                    "type": "uint",
                    "comment": "if state >= ARRAY_SIZE(oper_states)"
                }
            }
        },
        "address": {
            "type": "string",
            "attr": "IFLA_ADDRESS"
        },
        "flags": {
            "type": "array",
            "attr": "IFF_LOOPBACK, IFF_BROADCAST...IFF_*"
        },
        "addr_info": {
            "type": "array",
            "array": [
                {
                    "deleted": {
                        "type": "bool",
                        "attr": "RTM_DELADDR"
                    },
                    "family": {
                        "type": "string",
                        "attr": "ifa->ifa_family",
                        "mutually_exclusive": {
                            "family_index": {
                                "type": "uint",
                                "comment": "if family is not known"
                            }
                        }
                    },
                    "local": {
                        "type": "string",
                        "attr": "IFA_LOCAL"
                    },
                    "address": {
                        "type": "string",
                        "attr": "IFLA_LOCAL && IFA_ADDRESS"
                    },
                    "prefixlen": {
                        "type": "int",
                        "attr": "IFLA_LOCAL"
                    }
                }
            ]
        }
    }
]

$ ip -json -brief link show
[{
        "ifname": "lo",
        "operstate": "UNKNOWN",
        "address": "00:00:00:00:00:00",
        "flags": ["LOOPBACK","UP","LOWER_UP"]
    },{
        "ifname": "eth0",
        "operstate": "UP",
        "address": "08:00:27:db:31:88",
        "flags": ["BROADCAST","MULTICAST","UP","LOWER_UP"]
    },{
        "ifname": "swp1",
        "operstate": "DOWN",
        "address": "08:00:27:5b:b1:75",
        "flags": ["BROADCAST","MULTICAST"]
    },{
        "ifname": "vxlan42",
        "operstate": "DOWN",
        "address": "4a:d9:91:42:a2:d2",
        "flags": ["BROADCAST","MULTICAST"]
    },{
        "ifname": "bond0",
        "operstate": "DOWN",
        "address": "e2:aa:7b:17:c5:14",
        "flags": ["BROADCAST","MULTICAST","MASTER"]
    },{
        "link": "swp1",
        "ifname": "swp1.50",
        "operstate": "DOWN",
        "address": "08:00:27:5b:b1:75",
        "flags": ["BROADCAST","MULTICAST","M-DOWN"]
    },{
        "ifname": "br0",
        "operstate": "DOWN",
        "address": "08:00:27:5b:b1:75",
        "flags": ["NO-CARRIER","BROADCAST","MULTICAST","UP"]
    }
]

Schema for normal plus -details: ip -json -details link show

[
    {
        "deleted": {
            "type": "bool",
            "attr": "RTM_DELLINK"
        },
        "ifindex": {
            "type": "int"
        },
        "ifname": {
            "type": "string",
            "attr": "IFLA_IFNAME"
        },
        "link": {
            "type": "string",
            "attr": "IFLA_LINK",
            "mutually_exclusive": {
                "link_index": {
                    "type": "int",
                    "comment": "if IFLA_LINK_NETNSID exists"
                }
            }
        },
        "flags": {
            "type": "array",
            "attr": "IFF_LOOPBACK, IFF_BROADCAST...IFF_*"
        },
        "mtu": {
            "type": "int",
            "attr": "IFLA_MTU"
        },
        "xdp": {
            "type": "object",
            "attr": "IFLA_XDP",
            "object": {
                "mode": {
                    "type": "utin",
                    "attr": "IFLA_XDP_ATTACHED"
                },
                "prog_id": {
                    "type": "uint",
                    "attr": "IFLA_XDP_PROG_ID"
                }
            }
        },
        "qdisc": {
            "type": "string",
            "attr": "IFLA_QDISC"
        },
        "master": {
            "type": "string",
            "attr": "IFLA_MASTER"
        },
        "operstate": {
            "type": "string",
            "attr": "IFLA_OPERSTATE",
            "mutually_exclusive": {
                "operstate_index": {
                    "type": "uint",
                    "comment": "if state >= ARRAY_SIZE(oper_states)"
                }
            }
        },
        "linkmode": {
            "type": "string",
            "attr": "IFLA_LINKMODE",
            "mutually_exclusive": {
                "linkmode_index": {
                    "type": "uint",
                    "comment": "if mode >= ARRAY_SIZE(link_modes)"
                }
            }
        },
        "group": {
            "type": "string",
            "attr": "IFLA_GROUP"
        },
        "txqlen": {
            "type": "int",
            "attr": "IFLA_TXQLEN"
        },
        "event": {
            "type": "string",
            "attr": "IFLA_EVENT",
            "mutually_exclusive": {
                "event_index": {
                    "type": "uint",
                    "attr": "IFLA_OPERSTATE",
                    "comment": "if event >= ARRAY_SIZE(link_events)"
                }
            }
        },
        "link_type": {
            "type": "string",
            "attr": "ifi_type"
        },
        "address": {
            "type": "string",
            "attr": "IFLA_ADDRESS"
        },
        "link_pointtopoint": {
            "type": "bool",
            "attr": "IFF_POINTOPOINT"
        },
        "broadcast": {
            "type": "string",
            "attr": "IFLA_BROADCAST"
        },
        "link_netnsid": {
            "type": "int",
            "attr": "IFLA_LINK_NETNSID"
        },
        "proto_down": {
            "type": "bool",
            "attr": "IFLA_PROTO_DOWN"
        },

        //
        // if -details
        //

        "promiscuity": {
            "type": "uint",
            "attr": "IFLA_PROMISCUITY"
        },
        "linkinfo": {
            "type": "dict",
            "attr": "IFLA_LINKINFO",
            "dict": {
                "info_kind": {
                    "type": "string",
                    "attr": "IFLA_INFO_KIND"
                },
                "info_data": {
                    "type": "dict",
                    "attr": "IFLA_INFO_DATA",
                    "dict": {}
                },
                "info_xstats": {
                    "type": "dict",
                    "attr": "IFLA_INFO_XSTATS",
                    "dict": {}
                },
                "info_slave_data": {
                    "type": "dict",
                    "attr": "IFLA_INFO_SLAVE_DATA",
                    "dict": {}
                }
            }
        },
        "inet6_addr_gen_mode": {
            "type": "string",
            "attr": "IFLA_INET6_ADDR_GEN_MODE"
        },
        "num_tx_queues": {
            "type": "uint",
            "attr": "IFLA_NUM_TX_QUEUES"
        },
        "num_rx_queues": {
            "type": "uint",
            "attr": "IFLA_NUM_RX_QUEUES"
        },
        "gso_max_size": {
            "type": "uint",
            "attr": "IFLA_GSO_MAX_SIZE"
        },
        "gso_max_segs": {
            "type": "uint",
            "attr": "IFLA_GSO_MAX_SEGS"
        },
        "phys_port_name": {
            "type": "string",
            "attr": "IFLA_PHYS_PORT_NAME"
        },
        "phys_port_id": {
            "type": "string",
            "attr": "IFLA_PHYS_PORT_ID"
        },
        "phys_switch_id": {
            "type": "string",
            "attr": "IFLA_PHYS_SWITCH_ID"
        },
        "ifalias": {
            "type": "string",
            "attr": "IFLA_IFALIAS"
        },
        "stats": {
            "type": "dict",
            "attr": "IFLA_STATS",
            "dict": {
                "rx": {
                    "type": "dict",
                    "dict": {
                        "bytes": {
                            "type": "uint"
                        },
                        "packets": {
                            "type": "uint"
                        },
                        "errors": {
                            "type": "uint"
                        },
                        "dropped": {
                            "type": "uint"
                        },
                        "over_errors": {
                            "type": "uint"
                        },
                        "multicast": {
                            "type": "uint"
                        },
                        "compressed": {
                            "type": "uint"
                        },
                        "length_errors": {
                            "type": "uint"
                        },
                        "crc_errors": {
                            "type": "uint"
                        },
                        "frame_errors": {
                            "type": "uint"
                        },
                        "fifo_errors": {
                            "type": "uint"
                        },
                        "missed_errors": {
                            "type": "uint"
                        },
                        "nohandler": {
                            "type": "uint"
                        }
                    }
                },
                "tx": {
                    "type": "dict",
                    "dict": {
                        "bytes": {
                            "type": "uint"
                        },
                        "packets": {
                            "type": "uint"
                        },
                        "errors": {
                            "type": "uint"
                        },
                        "dropped": {
                            "type": "uint"
                        },
                        "carrier_errors": {
                            "type": "uint"
                        },
                        "collisions": {
                            "type": "uint"
                        },
                        "compressed": {
                            "type": "uint"
                        },
                        "aborted_errors": {
                            "type": "uint"
                        },
                        "fifo_errors": {
                            "type": "uint"
                        },
                        "window_errors": {
                            "type": "uint"
                        },
                        "heartbeat_errors": {
                            "type": "uint"
                        },
                        "carrier_changes": {
                            "type": "uint"
                        }
                    }
                }
            }
        },
        "stats64": {
            "type": "dict",
            "attr": "IFLA_STATS64",
            "dict": {
                "rx": {
                    "type": "dict",
                    "dict": {
                        "bytes": {
                            "type": "uint"
                        },
                        "packets": {
                            "type": "uint"
                        },
                        "errors": {
                            "type": "uint"
                        },
                        "dropped": {
                            "type": "uint"
                        },
                        "over_errors": {
                            "type": "uint"
                        },
                        "multicast": {
                            "type": "uint"
                        },
                        "compressed": {
                            "type": "uint"
                        },
                        "length_errors": {
                            "type": "uint"
                        },
                        "crc_errors": {
                            "type": "uint"
                        },
                        "frame_errors": {
                            "type": "uint"
                        },
                        "fifo_errors": {
                            "type": "uint"
                        },
                        "missed_errors": {
                            "type": "uint"
                        },
                        "nohandler": {
                            "type": "uint"
                        }
                    }
                },
                "tx": {
                    "type": "dict",
                    "dict": {
                        "bytes": {
                            "type": "uint"
                        },
                        "packets": {
                            "type": "uint"
                        },
                        "errors": {
                            "type": "uint"
                        },
                        "dropped": {
                            "type": "uint"
                        },
                        "carrier_errors": {
                            "type": "uint"
                        },
                        "collisions": {
                            "type": "uint"
                        },
                        "compressed": {
                            "type": "uint"
                        },
                        "aborted_errors": {
                            "type": "uint"
                        },
                        "fifo_errors": {
                            "type": "uint"
                        },
                        "window_errors": {
                            "type": "uint"
                        },
                        "heartbeat_errors": {
                            "type": "uint"
                        },
                        "carrier_changes": {
                            "type": "uint"
                        }
                    }
                }
            }
        },
        "vfinfo_list": {
            "type": "array",
            "attr": "IFLA_VFINFO_LIST",
            "array": [
                {
                    "vf": {
                        "type": "int"
                    },
                    "mac": {
                        "type": "string"
                    },
                    "vlan_list": {
                        "type": "array",
                        "attr": "IFLA_VF_VLAN_LIST",
                        "array": [
                            {
                                "vlan": {
                                    "type": "int"
                                },
                                "qos": {
                                    "type": "int"
                                },
                                "protocol": {
                                    "type": "string"
                                }
                            }
                        ]
                    },
                    "vlan": {
                        "type": "int",
                        "attr": "!IFLA_VF_VLAN_LIST && IFLA_VF_VLAN"
                    },
                    "qos": {
                        "type": "int",
                        "attr": "!IFLA_VF_VLAN_LIST && IFLA_VF_VLAN"
                    },
                    "tx_rate": {
                        "type": "int"
                    },
                    "rate": {
                        "type": "dict",
                        "attr": "IFLA_VF_RATE",
                        "dict": {
                            "max_tx": {
                                "type": "int"
                            },
                            "min_tx": {
                                "type": "int"
                            }
                        }
                    },
                    "spoofchk": {
                        "type": "bool",
                        "attr": "IFLA_VF_SPOOFCHK"
                    },
                    "link_state": {
                        "type": "string",
                        "attr": "IFLA_VF_LINK_STATE"
                    },
                    "trust": {
                        "type": "bool",
                        "attr": "IFLA_VF_TRUST"
                    },
                    "query_rss_en": {
                        "type": "bool",
                        "attr": "IFLA_VF_RSS_QUERY_EN"
                    },
                    "stats": {
                        "type": "dict",
                        "attr": "IFLA_VF_STATS",
                        "dict": {
                            "rx": {
                                "type": "dict",
                                "dict": {
                                    "bytes": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_RX_BYTES"
                                    },
                                    "packets": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_RX_PACKETS"
                                    },
                                    "multicast": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_MULTICAST"
                                    },
                                    "broadcast": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_BROADCAST"
                                    }
                                }
                            },
                            "tx": {
                                "type": "dict",
                                "dict": {
                                    "bytes": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_TX_BYTES"
                                    },
                                    "packets": {
                                        "type": "uint",
                                        "attr": "IFLA_VF_STATS_TX_PACKETS"
                                    }
                                }
                            }
                        }
                    }
                }
            ]
        }
    }
]

Example with the config previously given:
Note that here, linkinfo attributes are not populated.
The schemas are provided in each link type patches.

$ ip -details -json link show
[{
        "ifindex": 1,
        "ifname": "lo",
        "flags": ["LOOPBACK","UP","LOWER_UP"],
        "mtu": 65536,
        "qdisc": "noqueue",
        "operstate": "UNKNOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "link_type": "loopback",
        "address": "00:00:00:00:00:00",
        "broadcast": "00:00:00:00:00:00",
        "promiscuity": 0,
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 2,
        "ifname": "eth0",
        "flags": ["BROADCAST","MULTICAST","UP","LOWER_UP"],
        "mtu": 1500,
        "qdisc": "pfifo_fast",
        "operstate": "UP",
        "linkmode": "DEFAULT",
        "group": "default",
        "txqlen": 1000,
        "link_type": "ether",
        "address": "08:00:27:db:31:88",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 0,
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 3,
        "ifname": "swp1",
        "flags": ["BROADCAST","MULTICAST"],
        "mtu": 1500,
        "qdisc": "noop",
        "operstate": "DOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "txqlen": 1000,
        "link_type": "ether",
        "address": "08:00:27:5b:b1:75",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 0,
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 10,
        "ifname": "vxlan42",
        "flags": ["BROADCAST","MULTICAST"],
        "mtu": 1500,
        "qdisc": "noop",
        "master": "br0",
        "operstate": "DOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "link_type": "ether",
        "address": "4a:d9:91:42:a2:d2",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 1,
        "linkinfo": {
            "info_kind": "vxlan",
            "info_data": {},
            "info_slave_kind": "bridge",
            "info_slave_data": {}
        },
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 11,
        "ifname": "bond0",
        "flags": ["BROADCAST","MULTICAST","MASTER"],
        "mtu": 1500,
        "qdisc": "noop",
        "master": "br0",
        "operstate": "DOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "link_type": "ether",
        "address": "e2:aa:7b:17:c5:14",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 1,
        "linkinfo": {
            "info_kind": "bond",
            "info_data": {},
            "info_slave_kind": "bridge",
            "info_slave_data": {},
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 16,
        "num_rx_queues": 16,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 12,
        "ifname": "swp1.50",
        "link": "swp1",
        "flags": ["BROADCAST","MULTICAST","M-DOWN"],
        "mtu": 1500,
        "qdisc": "noop",
        "master": "br0",
        "operstate": "DOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "link_type": "ether",
        "address": "08:00:27:5b:b1:75",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 1,
        "linkinfo": {
            "info_kind": "vlan",
            "info_data": {},
            "info_slave_kind": "bridge",
            "info_slave_data": {},
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    },{
        "ifindex": 13,
        "ifname": "br0",
        "flags": ["NO-CARRIER","BROADCAST","MULTICAST","UP"],
        "mtu": 1500,
        "qdisc": "noqueue",
        "operstate": "DOWN",
        "linkmode": "DEFAULT",
        "group": "default",
        "link_type": "ether",
        "address": "08:00:27:5b:b1:75",
        "broadcast": "ff:ff:ff:ff:ff:ff",
        "promiscuity": 0,
        "linkinfo": {
            "info_kind": "bridge",
            "info_data": {},
        "inet6_addr_gen_mode": "eui64",
        "num_tx_queues": 1,
        "num_rx_queues": 1,
        "gso_max_size": 65536,
        "gso_max_segs": 65535
    }
]

Signed-off-by: Julien Fortin <jul...@cumulusnetworks.com>
---
 ip/ipaddress.c | 1064 +++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 753 insertions(+), 311 deletions(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 4d37c5e0..81a5888f 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -30,6 +30,7 @@
 #include <linux/sockios.h>
 #include <linux/net_namespace.h>
 
+#include "utils.h"
 #include "rt_names.h"
 #include "utils.h"
 #include "ll_map.h"
@@ -84,13 +85,14 @@ static void usage(void)
 
 static void print_link_flags(FILE *fp, unsigned int flags, unsigned int mdown)
 {
-       fprintf(fp, "<");
+       open_json_array(PRINT_ANY, is_json_context() ? "flags" : "<");
        if (flags & IFF_UP && !(flags & IFF_RUNNING))
-               fprintf(fp, "NO-CARRIER%s", flags ? "," : "");
+               print_string(PRINT_ANY, NULL,
+                            flags ? "%s," : "%s", "NO-CARRIER");
        flags &= ~IFF_RUNNING;
-#define _PF(f) if (flags&IFF_##f) { \
-                 flags &= ~IFF_##f ; \
-                 fprintf(fp, #f "%s", flags ? "," : ""); }
+#define _PF(f) if (flags&IFF_##f) {                                    \
+               flags &= ~IFF_##f ;                                     \
+               print_string(PRINT_ANY, NULL, flags ? "%s," : "%s", #f); }
        _PF(LOOPBACK);
        _PF(BROADCAST);
        _PF(POINTOPOINT);
@@ -111,10 +113,10 @@ static void print_link_flags(FILE *fp, unsigned int 
flags, unsigned int mdown)
        _PF(ECHO);
 #undef _PF
        if (flags)
-               fprintf(fp, "%x", flags);
+               print_hex(PRINT_ANY, NULL, "%x", flags);
        if (mdown)
-               fprintf(fp, ",M-DOWN");
-       fprintf(fp, "> ");
+               print_string(PRINT_ANY, NULL, ",%s", "M-DOWN");
+       close_json_array(PRINT_ANY, "> ");
 }
 
 static const char *oper_states[] = {
@@ -125,14 +127,26 @@ static const char *oper_states[] = {
 static void print_operstate(FILE *f, __u8 state)
 {
        if (state >= ARRAY_SIZE(oper_states)) {
-               fprintf(f, "state %#x ", state);
+               if (is_json_context())
+                       print_uint(PRINT_JSON, "operstate_index", NULL, state);
+               else
+                       print_0xhex(PRINT_FP, NULL, "state %#x", state);
        } else if (brief) {
-               color_fprintf(f, oper_state_color(state),
-                             "%-14s ", oper_states[state]);
+               print_color_string(PRINT_ANY,
+                                  oper_state_color(state),
+                                  "operstate",
+                                  "%-14s ",
+                                  oper_states[state]);
        } else {
-               fprintf(f, "state ");
-               color_fprintf(f, oper_state_color(state),
-                             "%s ", oper_states[state]);
+               if (is_json_context())
+                       print_string(PRINT_JSON,
+                                    "operstate",
+                                    NULL, oper_states[state]);
+               else {
+                       fprintf(f, "state ");
+                       color_fprintf(f, oper_state_color(state),
+                                     "%s ", oper_states[state]);
+               }
        }
 }
 
@@ -169,7 +183,7 @@ static void print_queuelen(FILE *f, struct rtattr 
*tb[IFLA_MAX + 1])
                qlen = ifr.ifr_qlen;
        }
        if (qlen)
-               fprintf(f, "qlen %d", qlen);
+               print_int(PRINT_ANY, "txqlen", "qlen %d", qlen);
 }
 
 static const char *link_modes[] = {
@@ -181,9 +195,15 @@ static void print_linkmode(FILE *f, struct rtattr *tb)
        unsigned int mode = rta_getattr_u8(tb);
 
        if (mode >= ARRAY_SIZE(link_modes))
-               fprintf(f, "mode %d ", mode);
+               print_int(PRINT_ANY,
+                         "linkmode_index",
+                         "mode %d ",
+                         mode);
        else
-               fprintf(f, "mode %s ", link_modes[mode]);
+               print_string(PRINT_ANY,
+                            "linkmode",
+                            "mode %s "
+                            , link_modes[mode]);
 }
 
 static char *parse_link_kind(struct rtattr *tb, bool slave)
@@ -215,13 +235,14 @@ static void print_linktype(FILE *fp, struct rtattr *tb)
        char slave[32];
 
        parse_rtattr_nested(linkinfo, IFLA_INFO_MAX, tb);
+       open_json_object("linkinfo");
 
        if (linkinfo[IFLA_INFO_KIND]) {
                const char *kind
                        = rta_getattr_str(linkinfo[IFLA_INFO_KIND]);
 
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    %s ", kind);
+               print_string(PRINT_FP, NULL, "%s", _SL_);
+               print_string(PRINT_ANY, "info_kind", "    %s ", kind);
 
                lu = get_link_kind(kind);
                if (lu && lu->print_opt) {
@@ -232,11 +253,16 @@ static void print_linktype(FILE *fp, struct rtattr *tb)
                                                    linkinfo[IFLA_INFO_DATA]);
                                data = attr;
                        }
+                       open_json_object("info_data");
                        lu->print_opt(lu, fp, data);
+                       close_json_object();
 
                        if (linkinfo[IFLA_INFO_XSTATS] && show_stats &&
-                           lu->print_xstats)
+                           lu->print_xstats) {
+                               open_json_object("info_xstats");
                                lu->print_xstats(lu, fp, 
linkinfo[IFLA_INFO_XSTATS]);
+                               close_json_object();
+                       }
                }
        }
 
@@ -244,8 +270,12 @@ static void print_linktype(FILE *fp, struct rtattr *tb)
                const char *slave_kind
                        = rta_getattr_str(linkinfo[IFLA_INFO_SLAVE_KIND]);
 
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    %s_slave ", slave_kind);
+               print_string(PRINT_FP, NULL, "%s", _SL_);
+               print_string(PRINT_ANY,
+                            "info_slave_kind",
+                            "    %s_slave ",
+                            slave_kind);
+
                snprintf(slave, sizeof(slave), "%s_slave", slave_kind);
 
                slave_lu = get_link_kind(slave);
@@ -257,9 +287,12 @@ static void print_linktype(FILE *fp, struct rtattr *tb)
                                                    
linkinfo[IFLA_INFO_SLAVE_DATA]);
                                data = attr;
                        }
+                       open_json_object("info_slave_data");
                        slave_lu->print_opt(slave_lu, fp, data);
+                       close_json_object();
                }
        }
+       close_json_object();
 }
 
 static void print_af_spec(FILE *fp, struct rtattr *af_spec_attr)
@@ -275,22 +308,39 @@ static void print_af_spec(FILE *fp, struct rtattr 
*af_spec_attr)
 
        if (tb[IFLA_INET6_ADDR_GEN_MODE]) {
                __u8 mode = rta_getattr_u8(tb[IFLA_INET6_ADDR_GEN_MODE]);
+               SPRINT_BUF(b1);
 
                switch (mode) {
                case IN6_ADDR_GEN_MODE_EUI64:
-                       fprintf(fp, "addrgenmode eui64 ");
+                       print_string(PRINT_ANY,
+                                    "inet6_addr_gen_mode",
+                                    "addrgenmode %s ",
+                                    "eui64");
                        break;
                case IN6_ADDR_GEN_MODE_NONE:
-                       fprintf(fp, "addrgenmode none ");
+                       print_string(PRINT_ANY,
+                                    "inet6_addr_gen_mode",
+                                    "addrgenmode %s ",
+                                    "none");
                        break;
                case IN6_ADDR_GEN_MODE_STABLE_PRIVACY:
-                       fprintf(fp, "addrgenmode stable_secret ");
+                       print_string(PRINT_ANY,
+                                    "inet6_addr_gen_mode",
+                                    "addrgenmode %s ",
+                                    "stable_secret");
                        break;
                case IN6_ADDR_GEN_MODE_RANDOM:
-                       fprintf(fp, "addrgenmode random ");
+                       print_string(PRINT_ANY,
+                                    "inet6_addr_gen_mode",
+                                    "addrgenmode %s ",
+                                    "random");
                        break;
                default:
-                       fprintf(fp, "addrgenmode %#.2hhx ", mode);
+                       snprintf(b1, sizeof(b1), "%#.2hhx", mode);
+                       print_string(PRINT_ANY,
+                                    "inet6_addr_gen_mode",
+                                    "addrgenmode %s ",
+                                    b1);
                        break;
                }
        }
@@ -316,83 +366,135 @@ static void print_vfinfo(FILE *fp, struct rtattr *vfinfo)
        vf_mac = RTA_DATA(vf[IFLA_VF_MAC]);
        vf_tx_rate = RTA_DATA(vf[IFLA_VF_TX_RATE]);
 
-       fprintf(fp, "%s    vf %d MAC %s", _SL_, vf_mac->vf,
-               ll_addr_n2a((unsigned char *)&vf_mac->mac,
-                           ETH_ALEN, 0, b1, sizeof(b1)));
+       print_string(PRINT_FP, NULL, "%s    ", _SL_);
+       print_int(PRINT_ANY, "vf", "vf %d ", vf_mac->vf);
+       print_string(PRINT_ANY, "mac", "MAC %s",
+                    ll_addr_n2a((unsigned char *) &vf_mac->mac,
+                                ETH_ALEN, 0, b1, sizeof(b1)));
+
        if (vf[IFLA_VF_VLAN_LIST]) {
                struct rtattr *i, *vfvlanlist = vf[IFLA_VF_VLAN_LIST];
                int rem = RTA_PAYLOAD(vfvlanlist);
 
+               open_json_array(PRINT_JSON, "vlan_list");
                for (i = RTA_DATA(vfvlanlist);
-                     RTA_OK(i, rem); i = RTA_NEXT(i, rem)) {
-                       struct ifla_vf_vlan_info *vf_vlan_info =
-                                       RTA_DATA(i);
+                    RTA_OK(i, rem); i = RTA_NEXT(i, rem)) {
+                       struct ifla_vf_vlan_info *vf_vlan_info = RTA_DATA(i);
                        SPRINT_BUF(b2);
 
+                       open_json_object(NULL);
                        if (vf_vlan_info->vlan)
-                               fprintf(fp, ", vlan %d", vf_vlan_info->vlan);
+                               print_int(PRINT_ANY,
+                                         "vlan",
+                                         ", vlan %d",
+                                         vf_vlan_info->vlan);
                        if (vf_vlan_info->qos)
-                               fprintf(fp, ", qos %d", vf_vlan_info->qos);
+                               print_int(PRINT_ANY,
+                                         "qos",
+                                         ", qos %d",
+                                         vf_vlan_info->qos);
                        if (vf_vlan_info->vlan_proto &&
                            vf_vlan_info->vlan_proto != htons(ETH_P_8021Q))
-                               fprintf(fp, ", vlan protocol %s",
-                                       ll_proto_n2a(vf_vlan_info->vlan_proto,
+                               print_string(PRINT_ANY,
+                                            "protocol",
+                                            ", vlan protocol %s",
+                                            ll_proto_n2a(
+                                                    vf_vlan_info->vlan_proto,
                                                     b2, sizeof(b2)));
-
+                       close_json_object();
                }
+               close_json_array(PRINT_JSON, NULL);
        } else {
                struct ifla_vf_vlan *vf_vlan = RTA_DATA(vf[IFLA_VF_VLAN]);
 
                if (vf_vlan->vlan)
-                       fprintf(fp, ", vlan %d", vf_vlan->vlan);
+                       print_int(PRINT_ANY,
+                                 "vlan",
+                                 ", vlan %d",
+                                 vf_vlan->vlan);
                if (vf_vlan->qos)
-                       fprintf(fp, ", qos %d", vf_vlan->qos);
+                       print_int(PRINT_ANY, "qos", ", qos %d", vf_vlan->qos);
        }
+
        if (vf_tx_rate->rate)
-               fprintf(fp, ", tx rate %d (Mbps)", vf_tx_rate->rate);
+               print_int(PRINT_ANY,
+                         "tx_rate",
+                         ", tx rate %d (Mbps)",
+                         vf_tx_rate->rate);
 
        if (vf[IFLA_VF_RATE]) {
                struct ifla_vf_rate *vf_rate = RTA_DATA(vf[IFLA_VF_RATE]);
-
-               if (vf_rate->max_tx_rate)
-                       fprintf(fp, ", max_tx_rate %dMbps", 
vf_rate->max_tx_rate);
-               if (vf_rate->min_tx_rate)
-                       fprintf(fp, ", min_tx_rate %dMbps", 
vf_rate->min_tx_rate);
+               int max_tx = vf_rate->max_tx_rate;
+               int min_tx = vf_rate->min_tx_rate;
+
+               if (is_json_context()) {
+                       open_json_object("rate");
+                       print_int(PRINT_JSON, "max_tx", NULL, max_tx);
+                       print_int(PRINT_ANY, "min_tx", NULL, min_tx);
+                       close_json_object();
+               } else {
+                       if (max_tx)
+                               fprintf(fp, ", max_tx_rate %dMbps", max_tx);
+                       if (min_tx)
+                               fprintf(fp, ", min_tx_rate %dMbps", min_tx);
+               }
        }
+
        if (vf[IFLA_VF_SPOOFCHK]) {
                struct ifla_vf_spoofchk *vf_spoofchk =
                        RTA_DATA(vf[IFLA_VF_SPOOFCHK]);
 
                if (vf_spoofchk->setting != -1)
-                       fprintf(fp, ", spoof checking %s",
-                               vf_spoofchk->setting ? "on" : "off");
+                       print_bool(PRINT_ANY,
+                                  "spoofchk",
+                                  vf_spoofchk->setting ?
+                                  ", spoof checking on" : ", spoof checking 
off",
+                                  vf_spoofchk->setting);
        }
+
        if (vf[IFLA_VF_LINK_STATE]) {
                struct ifla_vf_link_state *vf_linkstate =
                        RTA_DATA(vf[IFLA_VF_LINK_STATE]);
 
                if (vf_linkstate->link_state == IFLA_VF_LINK_STATE_AUTO)
-                       fprintf(fp, ", link-state auto");
+                       print_string(PRINT_ANY,
+                                    "link_state",
+                                    ", link-state %s",
+                                    "auto");
                else if (vf_linkstate->link_state == IFLA_VF_LINK_STATE_ENABLE)
-                       fprintf(fp, ", link-state enable");
+                       print_string(PRINT_ANY,
+                                    "link_state",
+                                    ", link-state %s",
+                                    "enable");
                else
-                       fprintf(fp, ", link-state disable");
+                       print_string(PRINT_ANY,
+                                    "link_state",
+                                    ", link-state %s",
+                                    "disable");
        }
+
        if (vf[IFLA_VF_TRUST]) {
                struct ifla_vf_trust *vf_trust = RTA_DATA(vf[IFLA_VF_TRUST]);
 
                if (vf_trust->setting != -1)
-                       fprintf(fp, ", trust %s",
-                               vf_trust->setting ? "on" : "off");
+                       print_bool(PRINT_ANY,
+                                  "trust",
+                                  vf_trust->setting ? ", trust on" : ", trust 
off",
+                                  vf_trust->setting);
        }
+
        if (vf[IFLA_VF_RSS_QUERY_EN]) {
                struct ifla_vf_rss_query_en *rss_query =
                        RTA_DATA(vf[IFLA_VF_RSS_QUERY_EN]);
 
                if (rss_query->setting != -1)
-                       fprintf(fp, ", query_rss %s",
-                               rss_query->setting ? "on" : "off");
+                       print_bool(PRINT_ANY,
+                                  "query_rss_en",
+                                  rss_query->setting ? ", query_rss on"
+                                  : ", query_rss off",
+                                  rss_query->setting);
        }
+
        if (vf[IFLA_VF_STATS] && show_stats)
                print_vf_stats64(fp, vf[IFLA_VF_STATS]);
 }
@@ -432,7 +534,7 @@ void print_num(FILE *fp, unsigned int width, uint64_t count)
        }
 
        snprintf(buf, sizeof(buf), "%.*f%c%s", precision,
-               (double) count / powi, *prefix, use_iec ? "i" : "");
+                (double) count / powi, *prefix, use_iec ? "i" : "");
 
        fprintf(fp, "%-*s ", width, buf);
 }
@@ -448,155 +550,339 @@ static void print_vf_stats64(FILE *fp, struct rtattr 
*vfstats)
 
        parse_rtattr_nested(vf, IFLA_VF_MAX, vfstats);
 
-       /* RX stats */
-       fprintf(fp, "%s", _SL_);
-       fprintf(fp, "    RX: bytes  packets  mcast   bcast %s", _SL_);
-       fprintf(fp, "    ");
+       if (is_json_context()) {
+               open_json_object("stats");
+
+               /* RX stats */
+               open_json_object("rx");
+               print_uint(PRINT_JSON, "bytes", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_RX_BYTES]));
+               print_uint(PRINT_JSON, "packets", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_RX_PACKETS]));
+               print_uint(PRINT_JSON, "multicast", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_MULTICAST]));
+               print_uint(PRINT_JSON, "broadcast", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_BROADCAST]));
+               close_json_object();
+
+               /* TX stats */
+               open_json_object("tx");
+               print_uint(PRINT_JSON, "tx_bytes", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_TX_BYTES]));
+               print_uint(PRINT_JSON, "tx_packets", NULL,
+                          rta_getattr_u64(vf[IFLA_VF_STATS_TX_PACKETS]));
+               close_json_object();
+               close_json_object();
+       } else {
+               /* RX stats */
+               fprintf(fp, "%s", _SL_);
+               fprintf(fp, "    RX: bytes  packets  mcast   bcast %s", _SL_);
+               fprintf(fp, "    ");
 
-       print_num(fp, 10,  rta_getattr_u64(vf[IFLA_VF_STATS_RX_BYTES]));
-       print_num(fp, 8, rta_getattr_u64(vf[IFLA_VF_STATS_RX_PACKETS]));
-       print_num(fp, 7, rta_getattr_u64(vf[IFLA_VF_STATS_MULTICAST]));
-       print_num(fp, 7, rta_getattr_u64(vf[IFLA_VF_STATS_BROADCAST]));
+               print_num(fp, 10, rta_getattr_u64(vf[IFLA_VF_STATS_RX_BYTES]));
+               print_num(fp, 8, rta_getattr_u64(vf[IFLA_VF_STATS_RX_PACKETS]));
+               print_num(fp, 7, rta_getattr_u64(vf[IFLA_VF_STATS_MULTICAST]));
+               print_num(fp, 7, rta_getattr_u64(vf[IFLA_VF_STATS_BROADCAST]));
 
-       /* TX stats */
-       fprintf(fp, "%s", _SL_);
-       fprintf(fp, "    TX: bytes  packets %s", _SL_);
-       fprintf(fp, "    ");
+               /* TX stats */
+               fprintf(fp, "%s", _SL_);
+               fprintf(fp, "    TX: bytes  packets %s", _SL_);
+               fprintf(fp, "    ");
 
-       print_num(fp, 10, rta_getattr_u64(vf[IFLA_VF_STATS_TX_BYTES]));
-       print_num(fp, 8, rta_getattr_u64(vf[IFLA_VF_STATS_TX_PACKETS]));
+               print_num(fp, 10, rta_getattr_u64(vf[IFLA_VF_STATS_TX_BYTES]));
+               print_num(fp, 8, rta_getattr_u64(vf[IFLA_VF_STATS_TX_PACKETS]));
+       }
 }
 
 static void print_link_stats64(FILE *fp, const struct rtnl_link_stats64 *s,
                               const struct rtattr *carrier_changes)
 {
-       /* RX stats */
-       fprintf(fp, "    RX: bytes  packets  errors  dropped overrun mcast   
%s%s",
-               s->rx_compressed ? "compressed" : "", _SL_);
-
-       fprintf(fp, "    ");
-       print_num(fp, 10, s->rx_bytes);
-       print_num(fp, 8, s->rx_packets);
-       print_num(fp, 7, s->rx_errors);
-       print_num(fp, 7, s->rx_dropped);
-       print_num(fp, 7, s->rx_over_errors);
-       print_num(fp, 7, s->multicast);
-       if (s->rx_compressed)
-               print_num(fp, 7, s->rx_compressed);
-
-       /* RX error stats */
-       if (show_stats > 1) {
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    RX errors: length   crc     frame   fifo    
missed%s%s",
-                       s->rx_nohandler ? "   nohandler" : "",  _SL_);
-
-               fprintf(fp, "               ");
-               print_num(fp, 8, s->rx_length_errors);
-               print_num(fp, 7, s->rx_crc_errors);
-               print_num(fp, 7, s->rx_frame_errors);
-               print_num(fp, 7, s->rx_fifo_errors);
-               print_num(fp, 7, s->rx_missed_errors);
-               if (s->rx_nohandler)
-                       print_num(fp, 7, s->rx_nohandler);
+       if (is_json_context()) {
+               open_json_object("stats644");
+
+               /* RX stats */
+               open_json_object("rx");
+               print_uint(PRINT_JSON, "bytes", NULL, s->rx_bytes);
+               print_uint(PRINT_JSON, "packets", NULL, s->rx_packets);
+               print_uint(PRINT_JSON, "errors", NULL, s->rx_errors);
+               print_uint(PRINT_JSON, "dropped", NULL, s->rx_dropped);
+               print_uint(PRINT_JSON, "over_errors", NULL, s->rx_over_errors);
+               print_uint(PRINT_JSON, "multicast", NULL, s->multicast);
+               if (s->rx_compressed)
+                       print_uint(PRINT_JSON,
+                                  "compressed",
+                                  NULL, s->rx_compressed);
+
+               /* RX error stats */
+               if (show_stats > 1) {
+                       print_uint(PRINT_JSON,
+                                  "length_errors",
+                                  NULL, s->rx_length_errors);
+                       print_uint(PRINT_JSON,
+                                  "crc_errors",
+                                  NULL, s->rx_crc_errors);
+                       print_uint(PRINT_JSON,
+                                  "frame_errors",
+                                  NULL, s->rx_frame_errors);
+                       print_uint(PRINT_JSON,
+                                  "fifo_errors",
+                                  NULL, s->rx_fifo_errors);
+                       print_uint(PRINT_JSON,
+                                  "missed_errors",
+                                  NULL, s->rx_missed_errors);
+                       if (s->rx_nohandler)
+                               print_uint(PRINT_JSON,
+                                          "nohandler", NULL, s->rx_nohandler);
+               }
+               close_json_object();
+
+               /* TX stats */
+               open_json_object("tx");
+               print_uint(PRINT_JSON, "bytes", NULL, s->tx_bytes);
+               print_uint(PRINT_JSON, "packets", NULL, s->tx_packets);
+               print_uint(PRINT_JSON, "errors", NULL, s->tx_errors);
+               print_uint(PRINT_JSON, "dropped", NULL, s->tx_dropped);
+               print_uint(PRINT_JSON,
+                          "carrier_errors",
+                          NULL, s->tx_carrier_errors);
+               print_uint(PRINT_JSON, "collisions", NULL, s->collisions);
+               if (s->tx_compressed)
+                       print_uint(PRINT_JSON,
+                                  "compressed",
+                                  NULL, s->tx_compressed);
+
+               /* TX error stats */
+               if (show_stats > 1) {
+                       print_uint(PRINT_JSON,
+                                  "aborted_errors",
+                                  NULL, s->tx_aborted_errors);
+                       print_uint(PRINT_JSON,
+                                  "fifo_errors",
+                                  NULL, s->tx_fifo_errors);
+                       print_uint(PRINT_JSON,
+                                  "window_errors",
+                                  NULL, s->tx_window_errors);
+                       print_uint(PRINT_JSON,
+                                  "heartbeat_errors",
+                                  NULL, s->tx_heartbeat_errors);
+                       if (carrier_changes)
+                               print_uint(PRINT_JSON, "carrier_changes", NULL,
+                                          rta_getattr_u32(carrier_changes));
+               }
+               close_json_object();
+               close_json_object();
 
-       }
-       fprintf(fp, "%s", _SL_);
+       } else {
+               /* RX stats */
+               fprintf(fp, "    RX: bytes  packets  errors  dropped overrun 
mcast   %s%s",
+                       s->rx_compressed ? "compressed" : "", _SL_);
+
+               fprintf(fp, "    ");
+               print_num(fp, 10, s->rx_bytes);
+               print_num(fp, 8, s->rx_packets);
+               print_num(fp, 7, s->rx_errors);
+               print_num(fp, 7, s->rx_dropped);
+               print_num(fp, 7, s->rx_over_errors);
+               print_num(fp, 7, s->multicast);
+               if (s->rx_compressed)
+                       print_num(fp, 7, s->rx_compressed);
+
+               /* RX error stats */
+               if (show_stats > 1) {
+                       fprintf(fp, "%s", _SL_);
+                       fprintf(fp, "    RX errors: length   crc     frame   
fifo    missed%s%s",
+                               s->rx_nohandler ? "   nohandler" : "", _SL_);
+
+                       fprintf(fp, "               ");
+                       print_num(fp, 8, s->rx_length_errors);
+                       print_num(fp, 7, s->rx_crc_errors);
+                       print_num(fp, 7, s->rx_frame_errors);
+                       print_num(fp, 7, s->rx_fifo_errors);
+                       print_num(fp, 7, s->rx_missed_errors);
+                       if (s->rx_nohandler)
+                               print_num(fp, 7, s->rx_nohandler);
 
-       /* TX stats */
-       fprintf(fp, "    TX: bytes  packets  errors  dropped carrier collsns 
%s%s",
-               s->tx_compressed ? "compressed" : "", _SL_);
-
-       fprintf(fp, "    ");
-       print_num(fp, 10, s->tx_bytes);
-       print_num(fp, 8, s->tx_packets);
-       print_num(fp, 7, s->tx_errors);
-       print_num(fp, 7, s->tx_dropped);
-       print_num(fp, 7, s->tx_carrier_errors);
-       print_num(fp, 7, s->collisions);
-       if (s->tx_compressed)
-               print_num(fp, 7, s->tx_compressed);
-
-       /* TX error stats */
-       if (show_stats > 1) {
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    TX errors: aborted  fifo   window heartbeat");
-               if (carrier_changes)
-                       fprintf(fp, " transns");
+               }
                fprintf(fp, "%s", _SL_);
 
-               fprintf(fp, "               ");
-               print_num(fp, 8, s->tx_aborted_errors);
-               print_num(fp, 7, s->tx_fifo_errors);
-               print_num(fp, 7, s->tx_window_errors);
-               print_num(fp, 7, s->tx_heartbeat_errors);
-               if (carrier_changes)
-                       print_num(fp, 7, rta_getattr_u32(carrier_changes));
+               /* TX stats */
+               fprintf(fp, "    TX: bytes  packets  errors  dropped carrier 
collsns %s%s",
+                       s->tx_compressed ? "compressed" : "", _SL_);
+
+               fprintf(fp, "    ");
+               print_num(fp, 10, s->tx_bytes);
+               print_num(fp, 8, s->tx_packets);
+               print_num(fp, 7, s->tx_errors);
+               print_num(fp, 7, s->tx_dropped);
+               print_num(fp, 7, s->tx_carrier_errors);
+               print_num(fp, 7, s->collisions);
+               if (s->tx_compressed)
+                       print_num(fp, 7, s->tx_compressed);
+
+               /* TX error stats */
+               if (show_stats > 1) {
+                       fprintf(fp, "%s", _SL_);
+                       fprintf(fp, "    TX errors: aborted  fifo   window 
heartbeat");
+                       if (carrier_changes)
+                               fprintf(fp, " transns");
+                       fprintf(fp, "%s", _SL_);
+
+                       fprintf(fp, "               ");
+                       print_num(fp, 8, s->tx_aborted_errors);
+                       print_num(fp, 7, s->tx_fifo_errors);
+                       print_num(fp, 7, s->tx_window_errors);
+                       print_num(fp, 7, s->tx_heartbeat_errors);
+                       if (carrier_changes)
+                               print_num(fp, 7,
+                                         rta_getattr_u32(carrier_changes));
+               }
        }
 }
 
 static void print_link_stats32(FILE *fp, const struct rtnl_link_stats *s,
                               const struct rtattr *carrier_changes)
 {
-       /* RX stats */
-       fprintf(fp, "    RX: bytes  packets  errors  dropped overrun mcast   
%s%s",
-               s->rx_compressed ? "compressed" : "", _SL_);
-
-
-       fprintf(fp, "    ");
-       print_num(fp, 10, s->rx_bytes);
-       print_num(fp, 8, s->rx_packets);
-       print_num(fp, 7, s->rx_errors);
-       print_num(fp, 7, s->rx_dropped);
-       print_num(fp, 7, s->rx_over_errors);
-       print_num(fp, 7, s->multicast);
-       if (s->rx_compressed)
-               print_num(fp, 7, s->rx_compressed);
-
-       /* RX error stats */
-       if (show_stats > 1) {
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    RX errors: length   crc     frame   fifo    
missed%s%s",
-                       s->rx_nohandler ? "   nohandler" : "",  _SL_);
-               fprintf(fp, "               ");
-               print_num(fp, 8, s->rx_length_errors);
-               print_num(fp, 7, s->rx_crc_errors);
-               print_num(fp, 7, s->rx_frame_errors);
-               print_num(fp, 7, s->rx_fifo_errors);
-               print_num(fp, 7, s->rx_missed_errors);
-               if (s->rx_nohandler)
-                       print_num(fp, 7, s->rx_nohandler);
-       }
-       fprintf(fp, "%s", _SL_);
+       if (is_json_context()) {
+               open_json_object("stats");
+
+               /* RX stats */
+               open_json_object("rx");
+               print_uint(PRINT_JSON, "bytes", NULL, s->rx_bytes);
+               print_uint(PRINT_JSON, "packets", NULL, s->rx_packets);
+               print_uint(PRINT_JSON, "errors", NULL, s->rx_errors);
+               print_uint(PRINT_JSON, "dropped", NULL, s->rx_dropped);
+               print_uint(PRINT_JSON, "over_errors", NULL, s->rx_over_errors);
+               print_uint(PRINT_JSON, "multicast", NULL, s->multicast);
+               if (s->rx_compressed)
+                       print_int(PRINT_JSON,
+                                 "compressed",
+                                 NULL, s->rx_compressed);
+
+               /* RX error stats */
+               if (show_stats > 1) {
+                       print_uint(PRINT_JSON,
+                                  "length_errors",
+                                  NULL, s->rx_length_errors);
+                       print_uint(PRINT_JSON,
+                                  "crc_errors",
+                                  NULL, s->rx_crc_errors);
+                       print_uint(PRINT_JSON,
+                                  "frame_errors",
+                                  NULL, s->rx_frame_errors);
+                       print_uint(PRINT_JSON,
+                                  "fifo_errors",
+                                  NULL, s->rx_fifo_errors);
+                       print_uint(PRINT_JSON,
+                                  "missed_errors",
+                                  NULL, s->rx_missed_errors);
+                       if (s->rx_nohandler)
+                               print_int(PRINT_JSON,
+                                         "nohandler",
+                                         NULL, s->rx_nohandler);
+               }
+               close_json_object();
+
+               /* TX stats */
+               open_json_object("tx");
+               print_uint(PRINT_JSON, "bytes", NULL, s->tx_bytes);
+               print_uint(PRINT_JSON, "packets", NULL, s->tx_packets);
+               print_uint(PRINT_JSON, "errors", NULL, s->tx_errors);
+               print_uint(PRINT_JSON, "dropped", NULL, s->tx_dropped);
+               print_uint(PRINT_JSON,
+                          "carrier_errors",
+                          NULL, s->tx_carrier_errors);
+               print_uint(PRINT_JSON, "collisions", NULL, s->collisions);
+               if (s->tx_compressed)
+                       print_int(PRINT_JSON,
+                                 "compressed",
+                                 NULL, s->tx_compressed);
+
+               /* TX error stats */
+               if (show_stats > 1) {
+                       print_uint(PRINT_JSON,
+                                  "aborted_errors",
+                                  NULL, s->tx_aborted_errors);
+                       print_uint(PRINT_JSON,
+                                  "fifo_errors",
+                                  NULL, s->tx_fifo_errors);
+                       print_uint(PRINT_JSON,
+                                  "window_errors",
+                                  NULL, s->tx_window_errors);
+                       print_uint(PRINT_JSON,
+                                  "heartbeat_errors",
+                                  NULL, s->tx_heartbeat_errors);
+                       if (carrier_changes)
+                               print_uint(PRINT_JSON,
+                                          "carrier_changes",
+                                          NULL,
+                                          rta_getattr_u32(carrier_changes));
+               }
 
-       /* TX stats */
-       fprintf(fp, "    TX: bytes  packets  errors  dropped carrier collsns 
%s%s",
-               s->tx_compressed ? "compressed" : "", _SL_);
-
-       fprintf(fp, "    ");
-       print_num(fp, 10, s->tx_bytes);
-       print_num(fp, 8, s->tx_packets);
-       print_num(fp, 7, s->tx_errors);
-       print_num(fp, 7, s->tx_dropped);
-       print_num(fp, 7, s->tx_carrier_errors);
-       print_num(fp, 7, s->collisions);
-       if (s->tx_compressed)
-               print_num(fp, 7, s->tx_compressed);
-
-       /* TX error stats */
-       if (show_stats > 1) {
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    TX errors: aborted  fifo   window heartbeat");
-               if (carrier_changes)
-                       fprintf(fp, " transns");
+               close_json_object();
+               close_json_object();
+       } else {
+               /* RX stats */
+               fprintf(fp, "    RX: bytes  packets  errors  dropped overrun 
mcast   %s%s",
+                       s->rx_compressed ? "compressed" : "", _SL_);
+
+
+               fprintf(fp, "    ");
+               print_num(fp, 10, s->rx_bytes);
+               print_num(fp, 8, s->rx_packets);
+               print_num(fp, 7, s->rx_errors);
+               print_num(fp, 7, s->rx_dropped);
+               print_num(fp, 7, s->rx_over_errors);
+               print_num(fp, 7, s->multicast);
+               if (s->rx_compressed)
+                       print_num(fp, 7, s->rx_compressed);
+
+               /* RX error stats */
+               if (show_stats > 1) {
+                       fprintf(fp, "%s", _SL_);
+                       fprintf(fp, "    RX errors: length   crc     frame   
fifo    missed%s%s",
+                               s->rx_nohandler ? "   nohandler" : "", _SL_);
+                       fprintf(fp, "               ");
+                       print_num(fp, 8, s->rx_length_errors);
+                       print_num(fp, 7, s->rx_crc_errors);
+                       print_num(fp, 7, s->rx_frame_errors);
+                       print_num(fp, 7, s->rx_fifo_errors);
+                       print_num(fp, 7, s->rx_missed_errors);
+                       if (s->rx_nohandler)
+                               print_num(fp, 7, s->rx_nohandler);
+               }
                fprintf(fp, "%s", _SL_);
 
-               fprintf(fp, "               ");
-               print_num(fp, 8, s->tx_aborted_errors);
-               print_num(fp, 7, s->tx_fifo_errors);
-               print_num(fp, 7, s->tx_window_errors);
-               print_num(fp, 7, s->tx_heartbeat_errors);
-               if (carrier_changes)
-                       print_num(fp, 7, rta_getattr_u32(carrier_changes));
+               /* TX stats */
+               fprintf(fp, "    TX: bytes  packets  errors  dropped carrier 
collsns %s%s",
+                       s->tx_compressed ? "compressed" : "", _SL_);
+
+               fprintf(fp, "    ");
+               print_num(fp, 10, s->tx_bytes);
+               print_num(fp, 8, s->tx_packets);
+               print_num(fp, 7, s->tx_errors);
+               print_num(fp, 7, s->tx_dropped);
+               print_num(fp, 7, s->tx_carrier_errors);
+               print_num(fp, 7, s->collisions);
+               if (s->tx_compressed)
+                       print_num(fp, 7, s->tx_compressed);
+
+               /* TX error stats */
+               if (show_stats > 1) {
+                       fprintf(fp, "%s", _SL_);
+                       fprintf(fp, "    TX errors: aborted  fifo   window 
heartbeat");
+                       if (carrier_changes)
+                               fprintf(fp, " transns");
+                       fprintf(fp, "%s", _SL_);
+
+                       fprintf(fp, "               ");
+                       print_num(fp, 8, s->tx_aborted_errors);
+                       print_num(fp, 7, s->tx_fifo_errors);
+                       print_num(fp, 7, s->tx_window_errors);
+                       print_num(fp, 7, s->tx_heartbeat_errors);
+                       if (carrier_changes)
+                               print_num(fp, 7,
+                                         rta_getattr_u32(carrier_changes));
+               }
        }
 }
 
@@ -694,44 +980,50 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
                return -1;
 
        if (n->nlmsg_type == RTM_DELLINK)
-               fprintf(fp, "Deleted ");
+               print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
        if (tb[IFLA_LINK]) {
                SPRINT_BUF(b1);
                int iflink = rta_getattr_u32(tb[IFLA_LINK]);
 
-               if (iflink == 0)
+               if (iflink == 0) {
                        snprintf(buf, sizeof(buf), "%s@NONE", name);
-               else {
-                       snprintf(buf, sizeof(buf),
-                                "%s@%s", name, ll_idx_n2a(iflink, b1));
+                       print_null(PRINT_JSON, "link", NULL, NULL);
+               } else {
+                       const char *link = ll_idx_n2a(iflink, b1);
+
+                       print_string(PRINT_JSON, "link", NULL, link);
+                       snprintf(buf, sizeof(buf), "%s@%s", name, link);
                        m_flag = ll_index_to_flags(iflink);
                        m_flag = !(m_flag & IFF_UP);
                }
        } else
                snprintf(buf, sizeof(buf), "%s", name);
 
-       fprintf(fp, "%-16s ", buf);
+       print_string(PRINT_FP, NULL, "%-16s ", buf);
+       print_string(PRINT_JSON, "ifname", NULL, name);
 
        if (tb[IFLA_OPERSTATE])
                print_operstate(fp, rta_getattr_u8(tb[IFLA_OPERSTATE]));
 
        if (pfilter->family == AF_PACKET) {
                SPRINT_BUF(b1);
+
                if (tb[IFLA_ADDRESS]) {
-                       color_fprintf(fp, COLOR_MAC, "%s ",
-                                       ll_addr_n2a(RTA_DATA(tb[IFLA_ADDRESS]),
-                                               RTA_PAYLOAD(tb[IFLA_ADDRESS]),
-                                               ifi->ifi_type,
-                                               b1, sizeof(b1)));
+                       print_color_string(PRINT_ANY, COLOR_MAC,
+                                          "address", "%s ",
+                                          ll_addr_n2a(
+                                                  RTA_DATA(tb[IFLA_ADDRESS]),
+                                                  
RTA_PAYLOAD(tb[IFLA_ADDRESS]),
+                                                  ifi->ifi_type,
+                                                  b1, sizeof(b1)));
                }
        }
 
-       if (pfilter->family == AF_PACKET)
+       if (pfilter->family == AF_PACKET) {
                print_link_flags(fp, ifi->ifi_flags, m_flag);
-
-       if (pfilter->family == AF_PACKET)
-               fprintf(fp, "\n");
+               print_string(PRINT_FP, NULL, "%s", "\n");
+       }
        fflush(fp);
        return 0;
 }
@@ -749,10 +1041,12 @@ static const char *link_events[] = {
 static void print_link_event(FILE *f, __u32 event)
 {
        if (event >= ARRAY_SIZE(link_events))
-               fprintf(f, "event %d ", event);
+               print_int(PRINT_ANY, "event", "event %d ", event);
        else {
                if (event)
-                       fprintf(f, "event %s ", link_events[event]);
+                       print_string(PRINT_ANY,
+                                    "event", "event %s ",
+                                    link_events[event]);
        }
 }
 
@@ -808,41 +1102,63 @@ int print_linkinfo(const struct sockaddr_nl *who,
                return -1;
 
        if (n->nlmsg_type == RTM_DELLINK)
-               fprintf(fp, "Deleted ");
-
-       fprintf(fp, "%d: ", ifi->ifi_index);
-       color_fprintf(fp, COLOR_IFNAME, "%s",
-                     tb[IFLA_IFNAME] ? rta_getattr_str(tb[IFLA_IFNAME]) : 
"<nil>");
+               print_bool(PRINT_ANY, "deleted", "Deleted ", true);
+
+       print_int(PRINT_ANY, "ifindex", "%d: ", ifi->ifi_index);
+       if (tb[IFLA_IFNAME]) {
+               print_color_string(PRINT_ANY,
+                                  COLOR_IFNAME,
+                                  "ifname", "%s",
+                                  rta_getattr_str(tb[IFLA_IFNAME]));
+       } else {
+               print_null(PRINT_JSON, "ifname", NULL, NULL);
+               print_color_null(PRINT_FP, COLOR_IFNAME,
+                                "ifname", "%s", "<nil>");
+       }
 
        if (tb[IFLA_LINK]) {
-               SPRINT_BUF(b1);
                int iflink = rta_getattr_u32(tb[IFLA_LINK]);
 
                if (iflink == 0)
-                       fprintf(fp, "@NONE: ");
+                       print_null(PRINT_ANY, "link", "@%s: ", "NONE");
                else {
                        if (tb[IFLA_LINK_NETNSID])
-                               fprintf(fp, "@if%d: ", iflink);
+                               print_int(PRINT_ANY,
+                                         "link_index", "@if%d: ", iflink);
                        else {
-                               fprintf(fp, "@%s: ", ll_idx_n2a(iflink, b1));
+                               SPRINT_BUF(b1);
+
+                               print_string(PRINT_ANY,
+                                            "link",
+                                            "@%s: ",
+                                            ll_idx_n2a(iflink, b1));
                                m_flag = ll_index_to_flags(iflink);
                                m_flag = !(m_flag & IFF_UP);
                        }
                }
        } else {
-               fprintf(fp, ": ");
+               print_string(PRINT_FP, NULL, ": ", NULL);
        }
        print_link_flags(fp, ifi->ifi_flags, m_flag);
 
        if (tb[IFLA_MTU])
-               fprintf(fp, "mtu %u ", rta_getattr_u32(tb[IFLA_MTU]));
+               print_int(PRINT_ANY,
+                         "mtu", "mtu %u ",
+                         rta_getattr_u32(tb[IFLA_MTU]));
        if (tb[IFLA_XDP])
                xdp_dump(fp, tb[IFLA_XDP]);
        if (tb[IFLA_QDISC])
-               fprintf(fp, "qdisc %s ", rta_getattr_str(tb[IFLA_QDISC]));
+               print_string(PRINT_ANY,
+                            "qdisc",
+                            "qdisc %s ",
+                            rta_getattr_str(tb[IFLA_QDISC]));
        if (tb[IFLA_MASTER]) {
                SPRINT_BUF(b1);
-               fprintf(fp, "master %s ", 
ll_idx_n2a(rta_getattr_u32(tb[IFLA_MASTER]), b1));
+
+               print_string(PRINT_ANY,
+                            "master",
+                            "master %s ",
+                            ll_idx_n2a(rta_getattr_u32(tb[IFLA_MASTER]), b1));
        }
 
        if (tb[IFLA_OPERSTATE])
@@ -855,7 +1171,10 @@ int print_linkinfo(const struct sockaddr_nl *who,
                SPRINT_BUF(b1);
                int group = rta_getattr_u32(tb[IFLA_GROUP]);
 
-               fprintf(fp, "group %s ", rtnl_group_n2a(group, b1, sizeof(b1)));
+               print_string(PRINT_ANY,
+                            "group",
+                            "group %s ",
+                            rtnl_group_n2a(group, b1, sizeof(b1)));
        }
 
        if (filter.showqueue)
@@ -866,47 +1185,68 @@ int print_linkinfo(const struct sockaddr_nl *who,
 
        if (!filter.family || filter.family == AF_PACKET || show_details) {
                SPRINT_BUF(b1);
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "    link/%s ", ll_type_n2a(ifi->ifi_type, b1, 
sizeof(b1)));
 
+               print_string(PRINT_FP, NULL, "%s", _SL_);
+               print_string(PRINT_ANY,
+                            "link_type",
+                            "    link/%s ",
+                            ll_type_n2a(ifi->ifi_type, b1, sizeof(b1)));
                if (tb[IFLA_ADDRESS]) {
-                       color_fprintf(fp, COLOR_MAC, "%s",
-                                     ll_addr_n2a(RTA_DATA(tb[IFLA_ADDRESS]),
-                                                 RTA_PAYLOAD(tb[IFLA_ADDRESS]),
-                                                 ifi->ifi_type,
-                                                 b1, sizeof(b1)));
+                       print_color_string(PRINT_ANY,
+                                          COLOR_MAC,
+                                          "address",
+                                          "%s",
+                                          
ll_addr_n2a(RTA_DATA(tb[IFLA_ADDRESS]),
+                                                      
RTA_PAYLOAD(tb[IFLA_ADDRESS]),
+                                                      ifi->ifi_type,
+                                                      b1, sizeof(b1)));
                }
                if (tb[IFLA_BROADCAST]) {
-                       if (ifi->ifi_flags&IFF_POINTOPOINT)
-                               fprintf(fp, " peer ");
-                       else
-                               fprintf(fp, " brd ");
-                       color_fprintf(fp, COLOR_MAC, "%s",
-                                     ll_addr_n2a(RTA_DATA(tb[IFLA_BROADCAST]),
-                                                 
RTA_PAYLOAD(tb[IFLA_BROADCAST]),
-                                                 ifi->ifi_type,
-                                                 b1, sizeof(b1)));
+                       if (ifi->ifi_flags&IFF_POINTOPOINT) {
+                               print_string(PRINT_FP, NULL, " peer ", NULL);
+                               print_bool(PRINT_JSON,
+                                          "link_pointtopoint", NULL, true);
+                       } else {
+                               print_string(PRINT_FP, NULL, " brd ", NULL);
+                       }
+                       print_color_string(PRINT_ANY,
+                                          COLOR_MAC,
+                                          "broadcast",
+                                          "%s",
+                                          
ll_addr_n2a(RTA_DATA(tb[IFLA_BROADCAST]),
+                                                      
RTA_PAYLOAD(tb[IFLA_BROADCAST]),
+                                                      ifi->ifi_type,
+                                                      b1, sizeof(b1)));
                }
        }
 
        if (tb[IFLA_LINK_NETNSID]) {
                int id = rta_getattr_u32(tb[IFLA_LINK_NETNSID]);
 
-               if (id >= 0)
-                       fprintf(fp, " link-netnsid %d", id);
-               else
-                       fprintf(fp, " link-netnsid unknown");
+               if (is_json_context()) {
+                       print_int(PRINT_JSON, "link_netnsid", NULL, id);
+               } else {
+                       if (id >= 0)
+                               print_int(PRINT_FP, NULL,
+                                         " link-netnsid %d", id);
+                       else
+                               print_string(PRINT_FP, NULL,
+                                            " link-netnsid %s", "unknown");
+               }
        }
 
        if (tb[IFLA_PROTO_DOWN]) {
                if (rta_getattr_u8(tb[IFLA_PROTO_DOWN]))
-                       fprintf(fp, " protodown on ");
+                       print_bool(PRINT_ANY,
+                                  "proto_down", " protodown on ", true);
        }
 
        if (show_details) {
                if (tb[IFLA_PROMISCUITY])
-                       fprintf(fp, " promiscuity %u ",
-                               rta_getattr_u32(tb[IFLA_PROMISCUITY]));
+                       print_uint(PRINT_ANY,
+                                  "promiscuity",
+                                  " promiscuity %u ",
+                                  rta_getattr_u32(tb[IFLA_PROMISCUITY]));
 
                if (tb[IFLA_LINKINFO])
                        print_linktype(fp, tb[IFLA_LINKINFO]);
@@ -915,50 +1255,68 @@ int print_linkinfo(const struct sockaddr_nl *who,
                        print_af_spec(fp, tb[IFLA_AF_SPEC]);
 
                if (tb[IFLA_NUM_TX_QUEUES])
-                       fprintf(fp, "numtxqueues %u ",
-                               rta_getattr_u32(tb[IFLA_NUM_TX_QUEUES]));
+                       print_uint(PRINT_ANY,
+                                  "num_tx_queues",
+                                  "numtxqueues %u ",
+                                  rta_getattr_u32(tb[IFLA_NUM_TX_QUEUES]));
 
                if (tb[IFLA_NUM_RX_QUEUES])
-                       fprintf(fp, "numrxqueues %u ",
-                               rta_getattr_u32(tb[IFLA_NUM_RX_QUEUES]));
+                       print_uint(PRINT_ANY,
+                                  "num_rx_queues",
+                                  "numrxqueues %u ",
+                                  rta_getattr_u32(tb[IFLA_NUM_RX_QUEUES]));
 
                if (tb[IFLA_GSO_MAX_SIZE])
-                       fprintf(fp, "gso_max_size %u ",
-                               rta_getattr_u32(tb[IFLA_GSO_MAX_SIZE]));
+                       print_uint(PRINT_ANY,
+                                  "gso_max_size",
+                                  "gso_max_size %u ",
+                                  rta_getattr_u32(tb[IFLA_GSO_MAX_SIZE]));
 
                if (tb[IFLA_GSO_MAX_SEGS])
-                       fprintf(fp, "gso_max_segs %u ",
-                               rta_getattr_u32(tb[IFLA_GSO_MAX_SEGS]));
+                       print_uint(PRINT_ANY,
+                                  "gso_max_segs",
+                                  "gso_max_segs %u ",
+                                  rta_getattr_u32(tb[IFLA_GSO_MAX_SEGS]));
 
                if (tb[IFLA_PHYS_PORT_NAME])
-                       fprintf(fp, "portname %s ",
-                               rta_getattr_str(tb[IFLA_PHYS_PORT_NAME]));
+                       print_string(PRINT_ANY,
+                                    "phys_port_name",
+                                    "portname %s ",
+                                    rta_getattr_str(tb[IFLA_PHYS_PORT_NAME]));
 
                if (tb[IFLA_PHYS_PORT_ID]) {
                        SPRINT_BUF(b1);
-                       fprintf(fp, "portid %s ",
-                               hexstring_n2a(RTA_DATA(tb[IFLA_PHYS_PORT_ID]),
-                                             
RTA_PAYLOAD(tb[IFLA_PHYS_PORT_ID]),
-                                             b1, sizeof(b1)));
+                       print_string(PRINT_ANY,
+                                    "phys_port_id",
+                                    "portid %s ",
+                                    hexstring_n2a(
+                                            RTA_DATA(tb[IFLA_PHYS_PORT_ID]),
+                                            RTA_PAYLOAD(tb[IFLA_PHYS_PORT_ID]),
+                                            b1, sizeof(b1)));
                }
 
                if (tb[IFLA_PHYS_SWITCH_ID]) {
                        SPRINT_BUF(b1);
-                       fprintf(fp, "switchid %s ",
-                               hexstring_n2a(RTA_DATA(tb[IFLA_PHYS_SWITCH_ID]),
-                                             
RTA_PAYLOAD(tb[IFLA_PHYS_SWITCH_ID]),
-                                             b1, sizeof(b1)));
+                       print_string(PRINT_ANY,
+                                    "phys_switch_id",
+                                    "switchid %s ",
+                                    
hexstring_n2a(RTA_DATA(tb[IFLA_PHYS_SWITCH_ID]),
+                                                  
RTA_PAYLOAD(tb[IFLA_PHYS_SWITCH_ID]),
+                                                  b1, sizeof(b1)));
                }
        }
 
 
        if ((do_link || show_details) && tb[IFLA_IFALIAS]) {
-               fprintf(fp, "%s    alias %s", _SL_,
-                       rta_getattr_str(tb[IFLA_IFALIAS]));
+               print_string(PRINT_FP, NULL, "%s    ", _SL_);
+               print_string(PRINT_ANY,
+                            "ifalias",
+                            "alias %s",
+                            rta_getattr_str(tb[IFLA_IFALIAS]));
        }
 
        if (do_link && show_stats) {
-               fprintf(fp, "%s", _SL_);
+               print_string(PRINT_FP, NULL, "%s", _SL_);
                __print_link_stats(fp, tb);
        }
 
@@ -966,11 +1324,16 @@ int print_linkinfo(const struct sockaddr_nl *who,
                struct rtattr *i, *vflist = tb[IFLA_VFINFO_LIST];
                int rem = RTA_PAYLOAD(vflist);
 
-               for (i = RTA_DATA(vflist); RTA_OK(i, rem); i = RTA_NEXT(i, rem))
+               open_json_array(PRINT_JSON, "vfinfo_list");
+               for (i = RTA_DATA(vflist); RTA_OK(i, rem); i = RTA_NEXT(i, 
rem)) {
+                       open_json_object(NULL);
                        print_vfinfo(fp, i);
+                       close_json_object();
+               }
+               close_json_array(PRINT_JSON, NULL);
        }
 
-       fprintf(fp, "\n");
+       print_string(PRINT_FP, NULL, "\n", NULL);
        fflush(fp);
        return 1;
 }
@@ -1009,7 +1372,7 @@ static unsigned int get_ifa_flags(struct ifaddrmsg *ifa,
                                  struct rtattr *ifa_flags_attr)
 {
        return ifa_flags_attr ? rta_getattr_u32(ifa_flags_attr) :
-                               ifa->ifa_flags;
+               ifa->ifa_flags;
 }
 
 /* Mapping from argument to address flag mask */
@@ -1042,20 +1405,34 @@ static void print_ifa_flags(FILE *fp, const struct 
ifaddrmsg *ifa,
 
                if (mask == IFA_F_PERMANENT) {
                        if (!(flags & mask))
-                               fprintf(fp, "dynamic ");
+                               print_bool(PRINT_ANY,
+                                          "dynamic", "dynamic ", true);
                } else if (flags & mask) {
                        if (mask == IFA_F_SECONDARY &&
-                           ifa->ifa_family == AF_INET6)
-                               fprintf(fp, "temporary ");
-                       else
-                               fprintf(fp, "%s ", ifa_flag_names[i].name);
+                           ifa->ifa_family == AF_INET6) {
+                               print_bool(PRINT_ANY,
+                                          "temporary", "temporary ", true);
+                       } else {
+                               print_string(PRINT_FP, NULL,
+                                            "%s ", ifa_flag_names[i].name);
+                               print_bool(PRINT_JSON,
+                                          ifa_flag_names[i].name, NULL, true);
+                       }
                }
 
                flags &= ~mask;
        }
 
-       if (flags)
-               fprintf(fp, "flags %02x ", flags);
+       if (flags) {
+               if (is_json_context()) {
+                       SPRINT_BUF(b1);
+
+                       snprintf(b1, sizeof(b1), "%02x", flags);
+                       print_string(PRINT_JSON, "ifa_flags", NULL, b1);
+               } else {
+                       fprintf(fp, "flags %02x ", flags);
+               }
+       }
 
 }
 
@@ -1176,80 +1553,130 @@ int print_addrinfo(const struct sockaddr_nl *who, 
struct nlmsghdr *n,
        }
 
        if (n->nlmsg_type == RTM_DELADDR)
-               fprintf(fp, "Deleted ");
+               print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
        if (!brief) {
-               if (filter.oneline || filter.flushb)
-                       fprintf(fp, "%u: %s", ifa->ifa_index, 
ll_index_to_name(ifa->ifa_index));
+               if (filter.oneline || filter.flushb) {
+                       const char *dev = ll_index_to_name(ifa->ifa_index);
+
+                       if (is_json_context()) {
+                               print_int(PRINT_JSON,
+                                         "index", NULL, ifa->ifa_index);
+                               print_string(PRINT_JSON, "dev", NULL, dev);
+                       } else {
+                               fprintf(fp, "%u: %s", ifa->ifa_index, dev);
+                       }
+               }
+
+               int family = ifa->ifa_family;
+
                if (ifa->ifa_family == AF_INET)
-                       fprintf(fp, "    inet ");
+                       print_string(PRINT_ANY, "family", "    %s ", "inet");
                else if (ifa->ifa_family == AF_INET6)
-                       fprintf(fp, "    inet6 ");
+                       print_string(PRINT_ANY, "family", "    %s ", "inet6");
                else if (ifa->ifa_family == AF_DECnet)
-                       fprintf(fp, "    dnet ");
+                       print_string(PRINT_ANY, "family", "    %s ", "dnet");
                else if (ifa->ifa_family == AF_IPX)
-                       fprintf(fp, "     ipx ");
+                       print_string(PRINT_ANY, "family", "     %s ", "ipx");
                else
-                       fprintf(fp, "    family %d ", ifa->ifa_family);
+                       print_int(PRINT_ANY,
+                                 "family_index",
+                                 "    family %d ", family);
        }
 
        if (rta_tb[IFA_LOCAL]) {
-               color_fprintf(fp, ifa_family_color(ifa->ifa_family), "%s",
-                             format_host_rta(ifa->ifa_family,
-                                             rta_tb[IFA_LOCAL]));
+               print_color_string(PRINT_ANY,
+                                  ifa_family_color(ifa->ifa_family),
+                                  "local", "%s",
+                                  format_host_rta(ifa->ifa_family,
+                                                  rta_tb[IFA_LOCAL]));
                if (rta_tb[IFA_ADDRESS] &&
                    memcmp(RTA_DATA(rta_tb[IFA_ADDRESS]),
                           RTA_DATA(rta_tb[IFA_LOCAL]),
                           ifa->ifa_family == AF_INET ? 4 : 16)) {
-                       fprintf(fp, " peer ");
-                       color_fprintf(fp, ifa_family_color(ifa->ifa_family),
-                                     "%s", format_host_rta(ifa->ifa_family,
-                                     rta_tb[IFA_ADDRESS]));
+                       print_string(PRINT_FP, NULL, " %s ", "peer");
+                       print_color_string(PRINT_ANY,
+                                          ifa_family_color(ifa->ifa_family),
+                                          "address",
+                                          "%s",
+                                          format_host_rta(ifa->ifa_family,
+                                                          
rta_tb[IFA_ADDRESS]));
                }
-               fprintf(fp, "/%d ", ifa->ifa_prefixlen);
+               print_int(PRINT_ANY, "prefixlen", "/%d", ifa->ifa_prefixlen);
        }
 
        if (brief)
                goto brief_exit;
 
        if (rta_tb[IFA_BROADCAST]) {
-               fprintf(fp, "brd ");
-               color_fprintf(fp, ifa_family_color(ifa->ifa_family), "%s ",
-                             format_host_rta(ifa->ifa_family,
-                                             rta_tb[IFA_BROADCAST]));
+               print_string(PRINT_FP, NULL, "%s ", "brd");
+               print_color_string(PRINT_ANY,
+                                  ifa_family_color(ifa->ifa_family),
+                                  "broadcast",
+                                  "%s ",
+                                  format_host_rta(ifa->ifa_family,
+                                                  rta_tb[IFA_BROADCAST]));
        }
+
        if (rta_tb[IFA_ANYCAST]) {
-               fprintf(fp, "any ");
-               color_fprintf(fp, ifa_family_color(ifa->ifa_family), "%s ",
-                             format_host_rta(ifa->ifa_family,
-                                             rta_tb[IFA_ANYCAST]));
+               print_string(PRINT_FP, NULL, "%s ", "any");
+               print_color_string(PRINT_ANY,
+                                  ifa_family_color(ifa->ifa_family),
+                                  "anycast",
+                                  "%s ",
+                                  format_host_rta(ifa->ifa_family,
+                                                  rta_tb[IFA_ANYCAST]));
        }
-       fprintf(fp, "scope %s ", rtnl_rtscope_n2a(ifa->ifa_scope, b1, 
sizeof(b1)));
+
+       print_string(PRINT_ANY,
+                    "scope",
+                    "scope %s ",
+                    rtnl_rtscope_n2a(ifa->ifa_scope, b1, sizeof(b1)));
 
        print_ifa_flags(fp, ifa, ifa_flags);
 
        if (rta_tb[IFA_LABEL])
-               fprintf(fp, "%s", rta_getattr_str(rta_tb[IFA_LABEL]));
+               print_string(PRINT_ANY,
+                            "label",
+                            "%s",
+                            rta_getattr_str(rta_tb[IFA_LABEL]));
+
        if (rta_tb[IFA_CACHEINFO]) {
                struct ifa_cacheinfo *ci = RTA_DATA(rta_tb[IFA_CACHEINFO]);
 
-               fprintf(fp, "%s", _SL_);
-               fprintf(fp, "       valid_lft ");
-               if (ci->ifa_valid == INFINITY_LIFE_TIME)
-                       fprintf(fp, "forever");
-               else
-                       fprintf(fp, "%usec", ci->ifa_valid);
-               fprintf(fp, " preferred_lft ");
-               if (ci->ifa_prefered == INFINITY_LIFE_TIME)
-                       fprintf(fp, "forever");
-               else {
+               print_string(PRINT_FP, NULL, "%s", _SL_);
+               print_string(PRINT_FP, NULL, "       valid_lft ", NULL);
+
+               if (ci->ifa_valid == INFINITY_LIFE_TIME) {
+                       print_uint(PRINT_JSON,
+                                  "valid_life_time",
+                                  NULL, INFINITY_LIFE_TIME);
+                       print_string(PRINT_FP, NULL, "%s", "forever");
+               } else {
+                       print_uint(PRINT_ANY,
+                                  "valid_life_time", "%usec", ci->ifa_valid);
+               }
+
+               print_string(PRINT_FP, NULL, " preferred_lft ", NULL);
+               if (ci->ifa_prefered == INFINITY_LIFE_TIME) {
+                       print_uint(PRINT_JSON,
+                                  "preferred_life_time",
+                                  NULL, INFINITY_LIFE_TIME);
+                       print_string(PRINT_FP, NULL, "%s", "forever");
+               } else {
                        if (ifa_flags & IFA_F_DEPRECATED)
-                               fprintf(fp, "%dsec", ci->ifa_prefered);
+                               print_int(PRINT_ANY,
+                                         "preferred_life_time",
+                                         "%dsec",
+                                         ci->ifa_prefered);
                        else
-                               fprintf(fp, "%usec", ci->ifa_prefered);
+                               print_uint(PRINT_ANY,
+                                          "preferred_life_time",
+                                          "%usec",
+                                          ci->ifa_prefered);
                }
        }
-       fprintf(fp, "\n");
+       print_string(PRINT_FP, NULL, "%s", "\n");
 brief_exit:
        fflush(fp);
        return 0;
@@ -1258,6 +1685,7 @@ brief_exit:
 static int print_selected_addrinfo(struct ifinfomsg *ifi,
                                   struct nlmsg_list *ainfo, FILE *fp)
 {
+       open_json_array(PRINT_JSON, "addr_info");
        for ( ; ainfo ;  ainfo = ainfo->next) {
                struct nlmsghdr *n = &ainfo->h;
                struct ifaddrmsg *ifa = NLMSG_DATA(n);
@@ -1275,10 +1703,14 @@ static int print_selected_addrinfo(struct ifinfomsg 
*ifi,
                if (filter.up && !(ifi->ifi_flags&IFF_UP))
                        continue;
 
+               open_json_object(NULL);
                print_addrinfo(NULL, n, fp);
+               close_json_object();
        }
+       close_json_array(PRINT_JSON, NULL);
+
        if (brief) {
-               fprintf(fp, "\n");
+               print_string(PRINT_FP, NULL, "%s", "\n");
                fflush(fp);
        }
        return 0;
@@ -1724,6 +2156,12 @@ static int ipaddr_list_flush_or_save(int argc, char 
**argv, int action)
                exit(0);
        }
 
+       /*
+        * Initialize a json_writer and open an array object
+        * if -json was specified.
+        */
+       new_json_obj(json, stdout);
+
        /*
         * If only filter_dev present and none of the other
         * link filters are present, use RTM_GETLINK to get
@@ -1732,8 +2170,10 @@ static int ipaddr_list_flush_or_save(int argc, char 
**argv, int action)
        if (filter_dev && filter.group == -1 && do_link == 1) {
                if (iplink_get(0, filter_dev, RTEXT_FILTER_VF) < 0) {
                        perror("Cannot send link get request");
+                       delete_json_obj();
                        exit(1);
                }
+               delete_json_obj();
                exit(0);
        }
 
@@ -1755,6 +2195,7 @@ static int ipaddr_list_flush_or_save(int argc, char 
**argv, int action)
                int res = 0;
                struct ifinfomsg *ifi = NLMSG_DATA(&l->h);
 
+               open_json_object(NULL);
                if (brief) {
                        if (print_linkinfo_brief(NULL, &l->h,
                                                 stdout, NULL) == 0)
@@ -1763,13 +2204,14 @@ static int ipaddr_list_flush_or_save(int argc, char 
**argv, int action)
                                                                ainfo->head,
                                                                stdout);
                } else if (no_link ||
-                         (res = print_linkinfo(NULL, &l->h, stdout)) >= 0) {
+                          (res = print_linkinfo(NULL, &l->h, stdout)) >= 0) {
                        if (filter.family != AF_PACKET)
                                print_selected_addrinfo(ifi,
                                                        ainfo->head, stdout);
                        if (res > 0 && !do_link && show_stats)
                                print_link_stats(stdout, &l->h);
                }
+               close_json_object();
        }
        fflush(stdout);
 
@@ -1777,7 +2219,7 @@ out:
        if (ainfo)
                free_nlmsg_chain(ainfo);
        free_nlmsg_chain(&linfo);
-
+       delete_json_obj();
        return 0;
 }
 
-- 
2.14.1

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