Displaying if ip addr is assigned statically or via DHCP

[ninjamarcus]

Using ip -j addr ls, converts the ip addr ls output into a json structure. We have been trying to get the same output with the netlink package but are stumbling at a few points. We are mostly interested in knowing if an ip address has been brought up by dhcp or assigned statically. The json output from ip commands shows - { "ifindex": 3, "ifname": "wlp0s20f3", "flags": [ "BROADCAST", "MULTICAST", "UP", "LOWER_UP" ], "mtu": 1500, "qdisc": "noqueue", "operstate": "UP", "group": "default", "txqlen": 1000, "link_type": "ether", "address": "4c:1d:96:7a:22:86", "broadcast": "ff:ff:ff:ff:ff:ff", "addr_info": [ { "family": "inet", "local": "192.168.65.90", "prefixlen": 18, "broadcast": "192.168.127.255", "scope": "global", "dynamic": true, "noprefixroute": true, "label": "wlp0s20f3", "valid_life_time": 6527, "preferred_life_time": 6527 },

The addr_info -> dynamic: true is the bit we are after. Given the ip command has it it must be available in netlink somewhere.

any suggestions would be welcomed.

[laeo]

Have you tried view the IP command source code? I have found this, and the flag is described in rtnetlink doc as

ifa_flags is a flag word of IFA_F_SECONDARY for secondary address (old alias interface), IFA_F_PERMANENT for a permanent address set by the user and other undocumented flags.

Hope this can helpful to you.

[fuqiangZ]

I processed like this (a.Flags&unix.IFA_F_PERMANENT != 0)