Public bug reported:
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
** Affects: procps (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1497166
Title:
10-ipv6-privacy.conf stomps on user-configured "privext" option
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