Detect if IP is static or obtained from DHCP on busybox

Question

I am working on embedded device who run BusyBox.
The system is getting its address by using the ip command. I want to figure out from my C program whether the device ip static or received from DHCP server. How do I do that?

I think you should edit your question with details on how you get the IP address in the first place. I assumed you ran BusyBox' dhcp client, but that seems wrong. — unwind, Oct 08 '09 at 13:20

score 4 · Answer 1 · answered May 27 '11 at 18:41

I don't know how your users interact with your embedded system. But on ours (same components) we have CLI that registers the chosen DHCP/STATIC type setting in a SHM struct (db) per interface.

Essentially, you need to keep track of how the IP of an interface was set.

score 1 · Answer 2 · answered Oct 08 '09 at 11:44

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The dumpleases command is supposed to show the current leases. I guess if you can determine that you have an IP address, but no lease, then the address is static.

answered Oct 08 '09 at 11:44

unwind

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the device get its address using ip command and not udhcp so dumpleases does not work – amitp Oct 08 '09 at 11:52

score 0 · Answer 3 · edited May 23 '17 at 12:29

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Take a look at this question and check the IFF_DYNAMIC flag - that may be set when DHCP is active on an interface.

edited May 23 '17 at 12:29

Community

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answered Oct 08 '09 at 12:07

Adam Liss

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IFF_DYNAMIC indicate dialup device with changing addresses – amitp Oct 08 '09 at 12:15
in Solaris there is IFF_DHCPRUNNING flag. Is there Linux equivalent ? – amitp Oct 08 '09 at 12:33

score 0 · Accepted Answer · answered Oct 08 '09 at 13:14

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If you control the enviroment, I suggest setting an env variable, or creating a flag file somewhere you can stat, when the IP adress is set.

answered Oct 08 '09 at 13:14

gnud

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Detect if IP is static or obtained from DHCP on busybox

4 Answers4