[Bug 1551351] Re: dhclient does not renew leases

[Andreas Mohr]

Major categorization aspects:
- this very important core functionality (properly reliable resource management of DHCP leases, also in suspend-to-RAM etc.) **NEVER EVER WORKS** (exclusively suspend-to-RAM use case here, ending up with stale IP address):
  - this did not work in 12.04LTS
  - this still did not work after upgrade to 14.04LTS
  - this STILL did not work after upgrade to 16.04LTS (recently upgraded, i.e. after activity of #12 which says that it DID work there, yet perhaps not suspend-to-RAM)
- importance of this bug should be "a lot higher than High"
  Justification:
  - messes with/breaks (CORRUPTS!!) environment even *beyond* local system scope (--> inacceptable!!), due to continuing communication via a stale IP address which has long since been re-assigned to other hosts (as can be verified via DNS query)
  - has been observed in *all* recent LTS releases (which are expected to work fine in large enterpriseish environments??)
--> Ubuntu release process is sorely missing reliable verification (persistently executed test case) for this core functionality, to ensure that this is (and keeps!) not causing damage, at least in production (stable) distributions

Example to achieve fixing stale IP (renew DHCP lease):
nmcli c
nmcli c down uuid <UUID>
nmcli c up uuid <UUID>

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https://bugs.launchpad.net/bugs/1551351

Title:
  dhclient does not renew leases

Status in bind9 package in Ubuntu:
  Fix Released
Status in isc-dhcp package in Ubuntu:
  Fix Released
Status in bind9 source package in Xenial:
  Fix Released
Status in isc-dhcp source package in Xenial:
  Fix Released

Bug description:
  Release: Xenial

  I think this only recently started after some bind9 updates triggered a rebuild. When booting dhclient gets started and acquires an IP address, but it does seem to lock up somewhere as it does not renew the lease.
  In my environment I set the lease time to 5 minutes, so I notice such things rather soon. I looked on the dhcp server side but saw any further dhcp messages come in from the client side.

  Related bugs:
   * bug 1551415:  systemctl stop networking hang / timeout 

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: isc-dhcp-client 4.3.3-5ubuntu8
  ProcVersionSignature: Ubuntu 4.4.0-9.24-generic 4.4.3
  Uname: Linux 4.4.0-9-generic x86_64
  ApportVersion: 2.20-0ubuntu3
  Architecture: amd64
  Date: Mon Feb 29 12:32:52 2016
  DhclientLeases:

  SourcePackage: isc-dhcp
  UpgradeStatus: No upgrade log present (probably fresh install)

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