New: Link-local addresses are used to go outside instead of assigned IPv6 routable address

https://bugzilla.kernel.org/show_bug.cgi?id=64011

            Bug ID: 64011
           Summary: Link-local addresses are used to go outside instead of
                    assigned IPv6 routable address
           Product: Networking
           Version: 2.5
    Kernel Version: 3.11.6-200 and earlier
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: IPV6
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

Created attachment 112651
--> https://bugzilla.kernel.org/attachment.cgi?id=112651&action=edit
pfSense screenshot of blocked link-local requests to outside

Sometimes kernel tries to estabilish a IPv6 connection to external global routable addresses using [FE80::] link-local addresses, instead of using the learned DHCPv6 global-unicast address.

In the attached screenshot, the machine got an IPv6 address in the [2001:1291:200::] range, and was correctly configured.

Since link-local should not traverse network segments, I am getting lots of events in my firewall from several kernel versions of different distros (see attachment).

At the time when the kernel attempts to use the link-local address, there is a small delay (around 1s) to open IPv6 pages. It appears kernel tries to reach a remote machine using link-local address. When it fails, the kernel uses the assigned global routable address.

This issue was seen on several major distros, as Fedora, Ubuntu, Mageia, etc. yet on the distro's later updates.