Messages in this thread | | | Date | Sat, 31 Jul 2021 22:30:54 +0200 | From | Pali Rohár <> | Subject | How to find out name or id of newly created interface |
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Hello!
Via rtnetlink API (RTM_NEWLINK/NLM_F_CREATE) it is possible to create a new network interface without specifying neither interface name nor id. This will let kernel to choose some interface name which does not conflicts with any already existing network interface. So seems like ideal way if I do not care about interface names. But at some stage it is needed to "configure" interface and for this action it is required to know interface id or name (as some ioctls use interface name instead of id).
And now I would like to know, how to race-free find out interface name (or id) of this newly created interface?
Response to RTM_NEWLINK/NLM_F_CREATE packet from kernel contains only buffer with struct nlmsgerr where is just error number (zero for success) without any additional information.
I can send another rtnetlink packet to request list of all existing network interfaces and expect that the interface with the highest id was that one which was created. But it is racy as another process may meanwhile create another network interface or it may delete this my newly created one, prior I send this followup packet.
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