Comment 0 for bug 1696415

I've found an issue on some of our Xenial office machines, causing NetworkManager to drop its IP address lease in some cases when it shouldn't. I'm not sure if the actual bug is in NetworkManager or perhaps dbus or dhclient, but I'll do my best to help to figure out where it is.

What appears to happen:
* NetworkManager is informed of a new IPv4 lease.
* During the lease, dhclient keeps it fresh by renewing it using DHCPREQUESTs regularly.
* In spite of this, NetworkManager drops the IP address from the interface when the last reported lease time expires.

This happens on various machines, once every few days. We are using a failover DHCP configuration using two machines (192.168.0.3 'bonaire' and 192.168.0.4 'curacao').

The machine where I've done the debugging is called 'pampus' (192.168.0.166). As you can see in the logs, at 01:21:06 NetworkManager reports a new lease with lease time 7200.

jun 07 01:21:06 pampus dhclient[1532]: DHCPREQUEST of 192.168.0.166 on eth0 to 192.168.0.4 port 67 (xid=0x3295b440)
jun 07 01:21:06 pampus dhclient[1532]: DHCPACK of 192.168.0.166 from 192.168.0.4
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] address 192.168.0.166
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] plen 24 (255.255.255.0)
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] gateway 192.168.0.5
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] server identifier 192.168.0.4
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] lease time 7200
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] nameserver '192.168.0.3'
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] nameserver '192.168.0.4'
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9530] domain name 'office.screenpointmed.com'
jun 07 01:21:06 pampus NetworkManager[1161]: <info> [1496791266.9531] dhcp4 (eth0): state changed bound -> bound

After this, dhclient is supposed to keep the lease fresh, which it does. E.g. at 03:13:19 you can see a DHCPREQUEST and DHCPACK; I've seen this DHCPACK in a tcpdump and it contains a new lease time of 7200 seconds.

jun 07 03:13:19 pampus dhclient[1532]: DHCPREQUEST of 192.168.0.166 on eth0 to 192.168.0.4 port 67 (xid=0x3295b440)
jun 07 03:13:19 pampus dhclient[1532]: DHCPACK of 192.168.0.166 from 192.168.0.4
jun 07 03:13:19 pampus dhclient[1532]: bound to 192.168.0.166 -- renewal in 2708 seconds.

However, at 03:21:07 (exactly 2 hours and 1 second after the last lease reported by NetworkManager) Avahi and NTP report that the IP address is gone:

jun 07 03:21:07 pampus avahi-daemon[1167]: Withdrawing address record for 192.168.0.166 on eth0.
jun 07 03:21:07 pampus avahi-daemon[1167]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.166.
jun 07 03:21:07 pampus avahi-daemon[1167]: Interface eth0.IPv4 no longer relevant for mDNS.
jun 07 03:21:08 pampus ntpd[18832]: Deleting interface #3 eth0, 192.168.0.166#123, interface stats: received=2512, sent=2549, dropped=0, active_time=111819 secs

So I suspect NetworkManager dropped the IP address from the interface, because it wasn't informed by dhclient that the lease was renewed. The logs don't explicitly say this, so I may have to turn on more verbose debugging logs in NetworkManager or dhclient to verify this.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: network-manager 1.2.6-0ubuntu0.16.04.1
ProcVersionSignature: Ubuntu 4.4.0-66.87-generic 4.4.44
Uname: Linux 4.4.0-66-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.6
Architecture: amd64
Date: Wed Jun 7 14:48:59 2017
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2016-11-04 (214 days ago)
InstallationMedia: Ubuntu 14.04.5 LTS "Trusty Tahr" - Release amd64 (20160803)
IpRoute:
 default via 192.168.0.5 dev eth0 proto static metric 100
 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.166
 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.166 metric 100
IwConfig:
 lo no wireless extensions.

 eth1 no wireless extensions.

 eth0 no wireless extensions.
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
RfKill:

SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)
nmcli-con:
 NAME UUID TYPE TIMESTAMP TIMESTAMP-REAL AUTOCONNECT AUTOCONNECT-PRIORITY READONLY DBUS-PATH ACTIVE DEVICE STATE ACTIVE-PATH
 Wired connection 1 37da1802-e1ce-3326-a6d0-f855cc32806d 802-3-ethernet 1496839466 wo 07 jun 2017 14:44:26 CEST yes 4294966297 no /org/freedesktop/NetworkManager/Settings/0 yes eth0 activated /org/freedesktop/NetworkManager/ActiveConnection/0
 Wired connection 2 a040d7fe-3c52-39ba-82b8-50fad0b602c1 802-3-ethernet 1496399665 vr 02 jun 2017 12:34:25 CEST yes 4294966297 no /org/freedesktop/NetworkManager/Settings/1 no -- -- --
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 eth0 ethernet connected /org/freedesktop/NetworkManager/Devices/0 Wired connection 1 37da1802-e1ce-3326-a6d0-f855cc32806d /org/freedesktop/NetworkManager/ActiveConnection/0
 eth1 ethernet unavailable /org/freedesktop/NetworkManager/Devices/2 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/1 -- -- --
nmcli-nm:
 RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN
 running 1.2.6 connected started full enabled enabled enabled enabled enabled