5.4 Losing a lease

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5.4.1 Lost by the network #

A lease is lost when a Rebinding client reaches the lease's end (§5.2), or when a NAK arrives while renewing or rebinding (§5.3). The client forgets the lease and enters Selecting, and netd acts on the interface's Address.OnExpiry:

  • Drop (the default): netd logs interface <name>: lease lost and forgets the lease. The next reconcile removes the address and the routes that came with it.
  • Keep: netd logs interface <name>: lease lost; keeping the address (Address.OnExpiry = Keep) at warning level and goes on desiring the lost lease — its address, gateway and routes — while the client looks for a new one. The kept lease is replaced the moment a new one binds.

With Keep, the status reply's lease describes the client, not the kept lease: it disappears with the client's lease, while the address stays on the interface.

Keep lasts while the client lasts. A stop (below) forgets the kept lease as it would any other.

5.4.2 Stopped by netd #

netd stops a client when:

  • the interface's outcome changes: another verdict, another profile, or any value of its profile edited (§3.3);
  • the interface loses carrier (§4.1);
  • the profile no longer wants a client (§5.1).

A client in Bound, Renewing or Rebinding sends a RELEASE to its server first: unicast from the lease address (§5.1, §5.6). After a carrier loss that RELEASE goes out on a link with no carrier, so the server never sees it. The client is then discarded, and the interface's lease and link-local address are forgotten, so the next reconcile removes both addresses.

A link that disappears from the kernel takes its client with it and sends nothing.

5.4.3 The operator's renew #

The control request renew (§9.2), and so net renew <interface>, moves a client in Bound, Renewing or Rebinding into Renewing at once: a new transaction id and a unicast REQUEST to the lease's server. The lease is not released first, and its address stays on the interface throughout. A client that holds no lease is left as it is, and the request still answers ok.

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