I have filed a separate ticket on this for ubuntu 16.04 and cherry-picked the linked fix and tested. https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1969901
I didn't see this ticket before I filed my ticket. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1533631 Title: dhclient killed when DHCPv6 lease is out-of date Status in NetworkManager: Fix Released Status in isc-dhcp package in Ubuntu: In Progress Status in network-manager package in Ubuntu: In Progress Bug description: Network Manager summarily kills the IPv6 dhclient process when the DHCPv6 lease contained in the dhclient6-${UUID}.lease file is out-of date, leaving the IPv6 interface without a stateful IPv6 address, or, if the "require IPv6 address on this interface" option is enabled, causes NM to cycle continuously deactivating and reactivating the interface (including the IPv4 addresses). This is effectively a Denial Of Service. It can be trivially induced if, for example, the dhclient6-$(UUID}.lease file contains a lease that was issued before the user went away on vacation or the PC wasn't connected to the same network for a few days (depending on the lease renew/rebind/expiry times). Calculation on the old lease of start + preferred_lifetime < NOW triggers dhclient to 'DEPREFER6' the lease (withdraw the address record) and ask the DHCPv6 server for a new lease, but Network Manager will kill the dhclient because it only sees an 'EXPIRE6' state change. In summary, when the DHCPv6 state transitions from "bound" to "unknown" then "expire" to "done" Network Manager kills the 'dhclient' process before it has chance to request and bind a fresh lease, If 'dhclient' is run manually with the same command-line options and allowed to continue running it correctly gains a new lease. Network Manager doesn't know how to handle "DEPREF6", which is sent from isc-dhcp dhclient to the helper script (set by "-sf" option). So it seems that to correctly solve this issue Network Manager must be taught how to handle DEPREF6. /var/log/syslog will show a message from dhclient of the form: dhclient: PRC: Address 2a02:8011:2007::2 depreferred. To manage notifications about this bug go to: https://bugs.launchpad.net/network-manager/+bug/1533631/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
