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[Tore Anderson <tore@xxxxxx>]

I just realised that this bug also impacts NetworkManager, at least on
Vivid: I set the property "ipv6.ip6-privacy" on the default wired
Ethernet interface to 0 (in order to prevent a remote CIFS mount from
freezing every few hours), however after a reboot, privacy extensions
remained active. My assumption is that NetworkManager configured the
interface correctly (without privacy extensions) early on during the
boot process, only to have the procps' 10-ipv6-privacy.conf overwrite it
moments later. Disabling 10-ipv6-privacy.conf solved this issue too.

** Summary changed:

- 10-ipv6-privacy.conf stomps on user-configured "privext" option
+ 10-ipv6-privacy.conf stomps on the ifup/NetworkManager "privext"/"ipv6.ip6-privacy" settings

** Also affects: ifupdown (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: network-manager (Ubuntu)
   Importance: Undecided
       Status: New

** Summary changed:

- 10-ipv6-privacy.conf stomps on the ifup/NetworkManager "privext"/"ipv6.ip6-privacy" settings
+ procps' 10-ipv6-privacy.conf stomps on the ifup/NetworkManager "privext"/"ipv6.ip6-privacy" settings

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https://bugs.launchpad.net/bugs/1497166

Title:
  procps' 10-ipv6-privacy.conf stomps on the ifup/NetworkManager
  "privext"/"ipv6.ip6-privacy" settings

Status in ifupdown package in Ubuntu:
  New
Status in network-manager package in Ubuntu:
  New
Status in procps package in Ubuntu:
  New

Bug description:
  I have configured the following in /etc/network/interfaces:

  auto eth0
  iface eth0 inet6 auto
    privext 0

  According to interfaces(5), this should disable IPv6 Privacy
  Extensions. However, after booting the machine,
  /proc/sys/net/ipv6/conf/eth0/use_tempaddr contains the value "2" -
  which means that Privacy Extensions are enabled. However running
  "ifdown eth0; ifup eth0" does fix the problem, so it is clear that
  ifup(8) does correctly set the use_tempaddr sysctl when bringing up
  the interface.

  What's going on is that sometime later in the bootup process, the
  procps package overrides the user-configured value and sets it
  unconditionally to "2" for every interface on the system. This happens
  because the file /etc/sysctl.d/10-ipv6-privacy.conf contains
  "net.ipv6.conf.all.use_tempaddr = 2". It should not, or this bug
  should be reassigned to the ifupdown package requesting for the
  removal of the defunct "privext" setting.

  On a related node, enabling IPv6 Privacy Extensions by default is
  counter to RFC 4941's recommendations. Quoting from section 3.6
  Deployment Considerations:

     The use of temporary addresses may cause unexpected difficulties with
     some applications.  As described below, some servers refuse to accept
     communications from clients for which they cannot map the IP address
     into a DNS name.  In addition, some applications may not behave
     robustly if temporary addresses are used and an address expires
     before the application has terminated, or if it opens multiple
     sessions, but expects them to all use the same addresses.
     Consequently, the use of temporary addresses SHOULD be disabled by
     default in order to minimize potential disruptions.  Individual
     applications, which have specific knowledge about the normal duration
     of connections, MAY override this as appropriate.

  As such, the most appropriate course of action is probably to stop
  shipping the 10-ipv6-privacy.conf file by default.

  The described behaviour is observed on Trusty LTS.

  Tore

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