dhclient fails to get address after latest patches

Bug #1606051 reported by Justin Alcorn on 2016-07-24
16
This bug affects 3 people
Affects Status Importance Assigned to Milestone
isc-dhcp (Ubuntu)
High
Unassigned

Bug Description

From ASkUbuntu entry http://askubuntu.com/questions/801136/recent-patches-broke-dhclient/802390

Running 16.04.01 LTS recently upgraded from 15.10. System is a home firewall with enp1s0 as LAN interface statically assigned and enp2s0 is WAN interface using DHCP, connected to modem.
Ran apt-get upgrade and on reboot enp2s0 had no address. running ifdown enp2s0 and then ifup enp2s0 gave me

root@sam:~# ifup enp2s0
Internet Systems Consortium DHCP Client 4.3.3
Copyright 2004-2015 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/enp2s0/d0:50:99:21:80:f8
Sending on LPF/enp2s0/d0:50:99:21:80:f8
Sending on Socket/fallback
DHCPDISCOVER on enp2s0 to 255.255.255.255 port 67 interval 3 (xid=0xd998571a)
send_packet: Network is down
dhclient.c:2098: Failed to send 300 byte long packet over enp2s0 interface.
receive_packet failed on enp2s0: Network is down
DHCPDISCOVER on enp2s0 to 255.255.255.255 port 67 interval 5 (xid=0xd998571a)
send_packet: Network is down
Running ifconfig enp2s0 up and dhclient enp2s0 gave similar results, but eventually /var/log/syslog showed a dhclient ipv4 lease being obtained - but the enp2s0 had only an IPv6 address, which appears to have come from avahi-daemon.

I then manually configured the enp2s0 interface with ifconfig enp2s0 xxx.xxx.xxx.xxx netmask 255.255.248.0 and put in a default route based on the lease info in dhclient.leases and I'm back online. But if I reboot or try to get dhclient to work, I continue to get the network is down errors.

apparmor is disabled, so that's not it. iptables is set to allow all DHCP traffic (67/udp and 68/udp) and all RELATED,ESTABLISHED traffic from enp2s0.

enp2s0 and enp2s0 are the same hardware.

root@sam:~# lshw -class network
  *-network
       description: Ethernet interface
   product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:01:00.0
   logical name: enp1s0
   version: 01
   serial: 04:8d:38:5d:20:17
   size: 100Mbit/s
   capacity: 1Gbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm vpd msi pciexpress bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full ip=yyy.yyy.yyy.yyy latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
   resources: irq:38 ioport:e000(size=256) memory:ffa00000-ffa00fff memory:ffa20000-ffa3ffff
  *-network
   description: Ethernet interface
   product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:02:00.0
   logical name: enp2s0
   version: 11
   serial: d0:50:99:21:80:f8
   size: 1Gbit/s
   capacity: 1Gbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168g-2_0.0.1 02/06/13 ip=xxx.xxx.xxx.xxx latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
   resources: irq:40 ioport:d000(size=256) memory:ff900000-ff900fff memory:d0800000-d0803fff
Ideas? remember, this happened right after patching.

networking network-manager dhclient

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: isc-dhcp-client 4.3.3-5ubuntu12.1
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Sun Jul 24 15:33:19 2016
InstallationDate: Installed on 2016-03-01 (145 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: isc-dhcp
UpgradeStatus: Upgraded to xenial on 2016-06-22 (32 days ago)
mtime.conffile..etc.dhcp.debug: 2016-06-28T18:13:33.371977

Justin Alcorn (3-justin) wrote :
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in isc-dhcp (Ubuntu):
status: New → Confirmed
Changed in isc-dhcp (Ubuntu):
importance: Undecided → High
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