** Description changed:

- After upgrading to Ubuntu 15.04 my computer is unable to obtain an IPv6
- address via DHCPv6. The root cause is that dhclient is exiting with the
- following message:
+ (Original bug description follows SRU info)
+ 
+ [Description]
+ 
+ When using dhcpv6 configured via ifupdown, the interface's dhcp client
+ fails to start at boot with the error:
+ 
+ Can't bind to dhcp address: Cannot assign requested address
+ 
+ This is because ifupdown doesn't wait, after bringing the interface up,
+ for it to complete its link-local Duplicate Address Detection (DAD), and
+ the dhcp client can't bind to the link-local address because it's still
+ in "tentative" state (until DAD completes).
+ 
+ This is fixed upstream in debian ifupdown in version 0.8.11 by adding
+ '-tentative' to the /lib/ifupdown/wait-for-ll6.sh script; before the
+ script was only waiting for the link-local address to appear, now it
+ waits until the link-local address appears and is not in 'tentative'
+ state.
+ 
+ [Test Case]
+ 
+ Configure an interface, using ifupdown, with dhcpv6 (e.g. iface eth0
+ inet6 dhcp) and reboot.  It will fail to get a dhcp address during boot.
+ 
+ [Regression]
+ 
+ None
+ 
+ 
+ -- original bug description --
+ 
+ 
+ After upgrading to Ubuntu 15.04 my computer is unable to obtain an IPv6 
address via DHCPv6. The root cause is that dhclient is exiting with the 
following message:
  
  -----------------------------------------------------
  Can't bind to dhcp address: Cannot assign requested address
  Please make sure there is no other dhcp server
  running and that there's no entry for dhcp or
  bootp in /etc/inetd.conf.   Also make sure you
  are not running HP JetAdmin software, which
  includes a bootp server.
  
  If you think you have received this message due to a bug rather
  than a configuration issue please read the section on submitting
  bugs on either our web page at www.isc.org or in the README file
  before submitting a bug.  These pages explain the proper
  process and the information we find helpful for debugging..
  
  exiting.
  -----------------------------------------------------
  
  The problem seems to exist in isc-dhcp-client 4.3.1-5ubuntu2 (15.04
  version) because downgrading to isc-dhcp-client 4.2.4-7ubuntu14 (14.10
  version) allows me to obtain an address.
  
  NetworkManager is the one launching dhclient. The two invocations (one
  for IPv4 and one for IPv6) are:
  
  dhclient_start(): running: /sbin/dhclient -d -q -sf
  /usr/lib/NetworkManager/nm-dhcp-helper -pf /run/sendsigs.omit.d/network-
  manager.dhclient-eth0.pid -lf /var/lib/NetworkManager/dhclient-c0a3dfde-
  5c0b-4cef-9c3b-563cfb1fb9d2-eth0.lease -cf /var/lib/NetworkManager
  /dhclient-eth0.conf eth0
  
  dhclient_start(): running: /sbin/dhclient -d -q -6 -N -sf
  /usr/lib/NetworkManager/nm-dhcp-helper -pf /run/sendsigs.omit.d/network-
  manager.dhclient6-eth0.pid -lf /var/lib/NetworkManager/dhclient6
  -c0a3dfde-5c0b-4cef-9c3b-563cfb1fb9d2-eth0.lease -cf
  /var/lib/NetworkManager/dhclient6-eth0.conf eth0
  
  I do not see anything suspicious with the way both dhclients are
  invoked.
  
  Given that a downgrade allows me to obtain an IPv6 address I think this
  might be a bug in the ISC DHCP client rather than in NetworkManager.

-- 
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https://bugs.launchpad.net/bugs/1447715

Title:
  dhclient -6: Can't bind to dhcp address: Cannot assign requested
  address

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