[Bug 1068756] Re: IPv6 Privacy Extensions enabled on Ubuntu Server by default

[Neil Wilson]

>From 'include/linux/in6.h'


/* RFC5014: Source address selection */
#define IPV6_ADDR_PREFERENCES   72

#define IPV6_PREFER_SRC_TMP             0x0001
#define IPV6_PREFER_SRC_PUBLIC          0x0002
#define IPV6_PREFER_SRC_PUBTMP_DEFAULT  0x0100
#define IPV6_PREFER_SRC_COA             0x0004
#define IPV6_PREFER_SRC_HOME            0x0400
#define IPV6_PREFER_SRC_CGA             0x0008
#define IPV6_PREFER_SRC_NONCGA          0x0800

so you need to call
setsockopt(socket, IPPROTO_IPV6, IPV6_ADDR_PREFERENCES, &value, sizeof(value)).

Where value=IPV6_PREFER_SRC_PUBLIC



On 16 May 2013 23:24, Jason Eggleston <jason at eggnet.com> wrote:
>
> I can confirm all of the security addresses by default are marked
> Global.  There is no application level workaround for this.
>
> $ ifconfig eth0 | awk '/inet6/ {print $1,$2,"ipv6addr",$4}'
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Link
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
> inet6 addr: ipv6addr Scope:Global
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1068756
>
> Title:
>   IPv6 Privacy Extensions enabled on Ubuntu Server by default
>
> To manage notifications about this bug go to:
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--
Neil Wilson

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https://bugs.launchpad.net/bugs/1068756

Title:
  IPv6 Privacy Extensions enabled on Ubuntu Server by default

Status in “procps” package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu 12.04 LTS and Ubuntu 12.10 server images both ship with the
  IPv6 Privacy Extensions enabled (as defined in RFC 4941[0]). Not only
  are they enabled, but these addresses are preferred over addresses
  obtained using SLAAC. While is may be considered a reasonable default
  on an image being used on a personal computer, it's not something that
  is sane to have enabled by default in a server environment. Having
  this extension enabled can wreak havoc if you are expecting a specific
  IPv6 address when you know the MAC addresses of your systems
  beforehand.

  The file that is responsible for causing this to be defaulted to
  enabled is: "/etc/sysctl.d/10-ipv6-privacy.conf". This file appears to
  be part of the procps package (as per the output of 'dpkg -S') and
  contains the following:

      # IPv6 Privacy Extensions (RFC 4941)
      # ---
      # IPv6 typically uses a device's MAC address when choosing an IPv6 address
      # to use in autoconfiguration. Privacy extensions allow using a randomly
      # generated IPv6 address, which increases privacy.
      #
      # Acceptable values:
      #    0 - don’t use privacy extensions.
      #    1 - generate privacy addresses
      #    2 - prefer privacy addresses and use them over the normal addresses.
      net.ipv6.conf.all.use_tempaddr = 2
      net.ipv6.conf.default.use_tempaddr = 2

  In short, IPv6 privacy extensions should not be enabled by default
  when deploying an Ubuntu server image. In a server environment you
  should be able to reliably determine your IPv6 address based on the
  MAC address of the system.

  Thank you for taking the time to look in to this as well as consider
  changing the default behavior of Ubuntu server.

  -Tim Heckman

  [0] http://tools.ietf.org/html/rfc4941

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