Bonding not working with IPv6

Can you please provide your /etc/network/interfaces as well as the output of "ifconfig -a"?

I am also hitting this issue with a very basic bonding example:

$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
bond-master bond0
bond-primary eth0

auto eth1
iface eth1 inet manual
bond-master bond0

auto bond0
iface bond0 inet dhcp
bond-mode active-backup
bond-miimon 100
bond-slaves none

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP group default qlen 1000
    link/ether 52:54:00:76:06:28 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5054:ff:fe76:628/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP group default qlen 1000
    link/ether 52:54:00:76:06:28 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5054:ff:fe76:628/64 scope link
       valid_lft forever preferred_lft forever
4: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether 52:54:00:76:06:28 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.224/24 brd 192.168.122.255 scope global bond0
       valid_lft forever preferred_lft forever
    inet6 fe80::5054:ff:fe76:628/64 scope link tentative dadfailed
       valid_lft forever preferred_lft forever

/var/log/kern.log:
Mar 19 21:52:49 lp1280362 kernel: [ 4.043238] bonding: Ethernet Channel Bonding Driver: v3.7.1 (April 27, 20
11)
Mar 19 21:52:49 lp1280362 kernel: [ 4.264717] kvm: Nested Virtualization enabled
Mar 19 21:52:49 lp1280362 kernel: [ 4.373163] ppdev: user-space parallel port driver
Mar 19 21:52:49 lp1280362 kernel: [ 4.581661] bonding: bond0: Setting MII monitoring interval to 100.
Mar 19 21:52:49 lp1280362 kernel: [ 4.592622] bonding: bond0: setting mode to active-backup (1).
Mar 19 21:52:49 lp1280362 kernel: [ 4.593091] IPv6: ADDRCONF(NETDEV_UP): bond0: link is not ready
Mar 19 21:52:49 lp1280362 kernel: [ 4.661884] bonding: bond0: Adding slave eth1.
Mar 19 21:52:49 lp1280362 kernel: [ 4.662189] 8139cp 0000:00:07.0 eth1: link up, 100Mbps, full-duplex, lpa 0
x05E1
Mar 19 21:52:49 lp1280362 kernel: [ 4.662363] bonding: bond0: making interface eth1 the new active one.
Mar 19 21:52:49 lp1280362 kernel: [ 4.664071] bonding: bond0: enslaving eth1 as an active interface with an
up link.
Mar 19 21:52:49 lp1280362 kernel: [ 4.664076] IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
Mar 19 21:52:49 lp1280362 kernel: [ 4.666837] bonding: bond0: Adding slave eth0.
Mar 19 21:52:49 lp1280362 kernel: [ 4.667201] bonding: bond0: enslaving eth0 as a backup interface with an u
p link.
Mar 19 21:52:49 lp1280362 kernel: [ 4.680131] bonding: bond0: Setting eth0 as primary slave.
Mar 19 21:52:49 lp1280362 kernel: [ 4.680132] bonding: bond0: making interface eth0 the new active one.
Mar 19 21:52:49 lp1280362 kernel: [ 4.752194] IPv6: bond0: IPv6 dupli...

Any progress on a fix?

In my Trusty with all updates for today it works with this configuration:
auto eth0
iface eth0 inet manual
  bond-master bond0
  bond-primary eth2

auto eth2
  iface eth2 inet manual
  bond-master bond0

auto bond0
iface bond0 inet static
  address 212.XXX.YYY.206
  netmask 255.255.255.0
  network 212.XXX.YYY.0
  gateway 212.XXX.YYY.1
  dns-nameservers 212.XXX.YYY.2

  bond-mode 4
  bond-miimon 100
  bond-slaves none
  bond-xmit_hash_policy 1

iface bond0 inet6 static
  address 2010:ZZZZ:WWWW:2::ce
  netmask 64
  gateway 2010:ZZZZ:WWWW:2::1

This is still a problem for 16.04