Oops, sorry :/

Yeah, it's kind of late, because then the package would need to go
through validation again and wait at least 7 days in proposed.

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https://bugs.launchpad.net/bugs/1038541

Title:
  Network Manager copies IPv6 route cache entries to main routing table

Status in NetworkManager:
  Fix Released
Status in “network-manager” package in Ubuntu:
  Fix Released
Status in “network-manager” source package in Precise:
  Fix Committed

Bug description:
  [Impact]
  This tends to break network connectivity to specific hosts if such hosts were 
accessed before a change in network topology.

  Specifically:
  - User pings a system;
  - User tries to connect to that system with SSH, it fails and the user 
realises they are not connected to a VPN required to reach that device.
  - User connects to the VPN
  - System is still unreachable because it is listed as reachable via the 
original network device rather than the new VPN-created network device.

  Or; the user changes from wired to wifi and loses connectivity to some
  systems because they were initially accessed over wired and the IPv6
  route remains via the old device.

  [Test Case]
  Requires a valid IPv6-enabled network.
  1) Connect to an IPv6 network.
  2) Ping Google via ipv6: 'ping6 ipv6.google.com'
  3) Observe whether 2607:f8b0:400c:c03::6a gets added to the IPv6 routing 
table:
  'ip -6 route'

  Without the patch, any host that gets packets sent to it will be added
  to the routing table; with the patch, such hosts are not listed in the
  routing table with the 'ip -6 route' command.

  
  [Regression Potential]
  Risk is minimal; the messages processed are not meant to be received by 
NetworkManager. A possible regression scenario would be if valid netlink 
messages for new routes would be generated by the kernel with the RTM_F_CLONED 
message when they indicate new network routes required due to a topology 
change, rather than new temporary cache routes for accessing a particular host; 
and would cause the new route to not be added (causing limited network 
unreachability).

  ---

  Any time an IPv6 route lookup happens, the kernel generates a new
  routing cache entry and notifies userspace using a netlink "new route"
  message with the RTM_F_CLONED flag set on the route.

  Network Manager doesn't check for this flag, so it accepts it as a new
  real route and adds it to its internal route cache. Then, because the
  event triggers an interface update, it synchronizes its route cache
  with the kernel table, putting the cache entry in as a real host
  route.

  I think NM might also overwrite the next hop of the route based on its
  internal idea of the default route, but I'm not sure.

  This causes problems if you have interfaces not managed by
  NetworkManager, such as manually configured VPNs, since these host
  routes override the route entries that send traffic down those
  interfaces rather than to the default router.

  To reproduce:
  Ensure "Ignore automatically obtained routes" is unchecked in Edit Connection 
-> IPv6 -> Routes, because this blocks the last stage (copying the spurious 
route back to the kernel).
  Connect to an IPv6 network.
  run `ip -6 route` and observe no extra routes
  run `ip -6 route get 2600::`
  run `ip -6 route` again and observe the new static route to 2600:: via your 
default gateway

  Expected behavior:
  No changes to routing table due to a route lookup.

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