[pkg-dhcp-devel] Bug#802036: isc-dhcp-client: ipv6 with alias interface: 'no link-local IPv6 address for eth0:1'

[Ralf Schlatterbeck]

Package: isc-dhcp-client
Version: 4.3.1-6
Severity: important
Tags: ipv6

Dear Maintainer,

I'm using the following config in /etc/network/interfaces:

auto eth0:1
iface eth0:1 inet6 dhcp
    accept_ra 2

The command
ifup --verbose eth0:1
shows:
run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
modprobe -q net-pf-10 > /dev/null 2>&1 || true # ignore failure.
sysctl -q -e -w net.ipv6.conf.eth0:1.accept_ra=2
ip link set dev eth0:1  up
dhclient -6 -pf /run/dhclient6.eth0:1.pid -lf /var/lib/dhcp/dhclient6.eth0:1.leases eth0:1
Failed to bring up eth0:1.

dhclient logs:
Oct 17 09:26:57 tux14 dhclient: no link-local IPv6 address for eth0:1
Oct 17 09:26:57 tux14 dhclient: 
Oct 17 09:26:57 tux14 dhclient: If you think you have received this message due to a bug rather
Oct 17 09:26:57 tux14 dhclient: than a configuration issue please read the section on submitting
Oct 17 09:26:57 tux14 dhclient: bugs on either our web page at www.isc.org or in the README file
Oct 17 09:26:57 tux14 dhclient: before submitting a bug.  These pages explain the proper
Oct 17 09:26:57 tux14 dhclient: process and the information we find helpful for debugging..
Oct 17 09:26:57 tux14 dhclient: 
Oct 17 09:26:57 tux14 dhclient: exiting.

Indeed the alias interface eth0:1 doesn't have a link local address.
But the main interface eth0 of course *does* have an IPv6 link-local address.
So maybe this is a bug in ifup/ifdown and the ifup logic should use eth0 instead.

Note that the same configuration works fine with debian wheezy
it doesn't work in current jessie. On a wheezy machine the alias
interface doesn't have an IPv6 Link-local address either.
And the ifup issues (almost, see below) the same commands on wheezy.
So my guess is that the check for an existing link-local address
is new in dhclient and breaks things.

The command
ifup --verbose eth0:1
on a comparable wheezy machine works:
run-parts --verbose /etc/network/if-pre-up.d
modprobe -q net-pf-10 > /dev/null 2>&1 || true # ignore failure.
sysctl -q -e -w net.ipv6.conf.eth0:1.accept_ra=2
ip link set dev eth0:1  up
dhclient -6 -pf /run/dhclient6.eth0:1.pid -lf /var/lib/dhcp/dhclient6.eth0:1.leases eth0:1
run-parts --verbose /etc/network/if-up.d
...

ifconfig eth0 shows (I have an IPv4 configuration that works)
(note that this is a KVM virtual machine, therefore the 
peculiar mac address):
root at tux14:~# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 52:54:08:15:01:14  
          inet addr:10.33.33.14  Bcast:10.33.33.255  Mask:255.255.255.0
          inet6 addr: fe80::5054:8ff:fe15:114/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5860441 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5609388 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:982792433 (937.2 MiB)  TX bytes:1043229289 (994.9 MiB)

root at tux14:~# ifconfig eth0:1
eth0:1    Link encap:Ethernet  HWaddr 52:54:08:15:01:14  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1



-- System Information:
Debian Release: 8.2
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages isc-dhcp-client depends on:
ii  debianutils       4.4+b1
ii  iproute2          3.16.0-2
ii  isc-dhcp-common   4.3.1-6
ii  libc6             2.19-18+deb8u1
ii  libdns-export100  1:9.9.5.dfsg-9+deb8u3
ii  libirs-export91   1:9.9.5.dfsg-9+deb8u3
ii  libisc-export95   1:9.9.5.dfsg-9+deb8u3

isc-dhcp-client recommends no packages.

Versions of packages isc-dhcp-client suggests:
pn  avahi-autoipd  <none>
pn  resolvconf     <none>

-- no debconf information