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[Bug 1284535] Re: Make IPV6_[RECV]PKTINFO work for IPv4-mapped addresses


I'm using kernel 3.2. This issue was fixed in 3.14. But I still have
this issue with 3.2.

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  Make IPV6_[RECV]PKTINFO work for IPv4-mapped addresses

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Released

Bug description:
  Currently, the Linux kernel doesn't provide IPV6_RECVPKTINFO ancillary
  data on datagrams coming in from IPv4-mapped clients (e.g.,
  ::ffff: on INET6 sockets in the default dual personality
  mode, nor does it honour IPV6_PKTINFO when sending datagrams on such a
  socket to an IPv4-mapped destination.

  This means that an UDP application that requires a server to respond
  with the same address as it was contacted on cannot reliably work for
  IPv4 clients, because 1) the server has no way of knowing which
  address it was contacted on, and even if it did, 2) the kernel would
  ignore requests to use a specific source address.

  For a real-life manifestation of this problem, see this OpenVPN bug
  report: https://community.openvpn.net/openvpn/ticket/306

  This has recently been fixed in the net-next upstream tree with the
  following commits (the first one of which made the 3.14 merge window,
  the second one will be in 3.15):


  Enabling IPv6 is getting increasingly important in these days, but at
  the same time maintaining backwards compatibility with IPv4-only
  clients is also essential. I'm therefore requesting a backport of the
  above two commits to the Ubuntu LTS kernel images so that it becomes
  possible to use OpenVPN (and any other software packages) in dual-
  stack mode.


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