On Wed, Oct 22, 2014 at 12:19 PM, Lennart Poettering
<lenn...@poettering.net> wrote:
> On Sat, 13.09.14 20:40, Tom Gundersen (t...@jklm.no) wrote:
>
>> Yeah, this could happen. It so happens that the loopback link will
>> always have ifindex 1, so I guess we could just fall back to checking
>> for that if we don't have the real flags.
>
> Is that true even in network namespaces? Is this really exported API?
> I really don't want to rely on behaviour here that is not considered
> official API of Linux.
>
> If it is safe API of Linux, then we really should drop
> manager_ifindex_is_loopback() entirely, and just always compare the
> ifindex.
>
> Anyone has some pointers where this is made API?
We may want to ask the kernel guys to export LOOPBACK_IFINDEX, as it
is not at the moment. However, I think relying on it is fine even
without that as the kernel will BUG_ON if "lo" does not have ifindex
1[0], and no other netdev can have ifindex 1[1]:
/* The loopback device is special if any other network devices
* is present in a network namespace the loopback device must
* be present.
Changing these invariants would surely break lots of stuff, so cannot happen.
I'd be happy to push for this to be made explicit though.
Cheers,
Tom
[0]:
<https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/net/loopback.c#n207>
[1]:
<https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/core/dev.c#n7260>
_______________________________________________
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/systemd-devel
