[BUG] Any-IP IPv6 support broken

[BUG] Any-IP IPv6 support broken

[Gilberto Bertin]

Hello,
testing Any-IP on my machine, I noticed that it's not working with IPv6
addresses.
Tests are performed on a 4.1 kernel.

Steps to reproduce the bug:

1- make sure Any-IP is working with IPv4 addresses:

# ip -4 route add local 4.4.4.0/24 dev eth0

with this command every packets with an IP in the subnet 4.4.4.0/24 will
be delivered to the eth0 interface.
We can test this:

$ ping 4.4.4.1 -c 1 | grep received
1 packets transmitted, 1 received, 0% packet loss, time 0ms
$ ping 4.4.4.50 -c 1 | grep received
1 packets transmitted, 1 received, 0% packet loss, time 0ms
$ ping 4.4.4.200 -c 1 | grep received
1 packets transmitted, 1 received, 0% packet loss, time 0ms

2- note that it's not actually working with IPv6 addresses:

# ip -6 route add local abcd:abcd:abcd:abcd::/64 dev eth0

$ ping6 -c 1 abcd:abcd:abcd:abcd::1 | grep received
1 packets transmitted, 0 received, 100% packet loss, time 0ms
$ ping6 -c 1 abcd:abcd:abcd:abcd::50 | grep received
1 packets transmitted, 0 received, 100% packet loss, time 0ms
$ ping6 -c 1 abcd:abcd:abcd:abcd::100 | grep received
1 packets transmitted, 0 received, 100% packet loss, time 0ms

Since the kernel should support Any-IP with IPv6 addresses (the patch
was submitted/accepted years ago [1]) I suspect this is a bug.

Even trying with the commands suggested by the patch [1]:
# ip -6 rule  add from all iif eth0 lookup 200
# ip -6 route add local default dev lo table 200

I was not able to get it working.


Thank you.

[1] http://www.spinics.net/lists/netdev/msg141994.html

Re: [BUG] Any-IP IPv6 support broken

[Eric Dumazet]

On Thu, 2015-10-29 at 15:00 +0000, Gilberto Bertin wrote:
> Hello,
> testing Any-IP on my machine, I noticed that it's not working with IPv6
> addresses.
> Tests are performed on a 4.1 kernel.
> 
> Steps to reproduce the bug:
> 
> 1- make sure Any-IP is working with IPv4 addresses:
> 
> # ip -4 route add local 4.4.4.0/24 dev eth0
> 
> with this command every packets with an IP in the subnet 4.4.4.0/24 will
> be delivered to the eth0 interface.
> We can test this:
> 
> $ ping 4.4.4.1 -c 1 | grep received
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> $ ping 4.4.4.50 -c 1 | grep received
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> $ ping 4.4.4.200 -c 1 | grep received
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> 
> 2- note that it's not actually working with IPv6 addresses:
> 
> # ip -6 route add local abcd:abcd:abcd:abcd::/64 dev eth0
> 
> $ ping6 -c 1 abcd:abcd:abcd:abcd::1 | grep received
> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
> $ ping6 -c 1 abcd:abcd:abcd:abcd::50 | grep received
> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
> $ ping6 -c 1 abcd:abcd:abcd:abcd::100 | grep received
> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
> 
> Since the kernel should support Any-IP with IPv6 addresses (the patch
> was submitted/accepted years ago [1]) I suspect this is a bug.
> 
> Even trying with the commands suggested by the patch [1]:
> # ip -6 rule  add from all iif eth0 lookup 200
> # ip -6 route add local default dev lo table 200
> 
> I was not able to get it working.
> 
> 
> Thank you.
> 
> [1] http://www.spinics.net/lists/netdev/msg141994.html
> 


CC Maciej

Re: [BUG] Any-IP IPv6 support broken

[Maciej Żenczykowski]

What are you trying to do?

The intent of the patch is to be able to terminate connections from
outside the machine that are reaching the machine (perhaps delivered
inside a tunnel or via some other mechanism: static arp entries,
routing via the machine, etc), that the kernel wouldn't normally think
were destined for the host.

You can't really test it from within the machine (unless you use
network namespaces).

Does what you're trying to do work on an older kernel?  Which kernel
version does it break at?

btw. afaik any-ip doesn't work with IPv4 on any un-patched kernel (the
IPv4 support patch was reverted).

Re: [BUG] Any-IP IPv6 support broken

[Gilberto Bertin]

> On 29 Oct 2015, at 17:44, Maciej Żenczykowski <zenczykowski@gmail.com> wrote:
> 
> What are you trying to do?

I would like to have a "bind-to-subnet" semantic with IPv6.

This is currently working with IPv4, and the setup is the follow:

- setup a dummy network device configured with any-IP
- add an any-IP route
- bind() on the dummy device

in this way we can effectively bind a process to a particular subnet
(by binding it to a dummy device which is receiving all the packets
from a particular subnet).

The point of using dummy devices is that we can configure multiple ones
(and so we can bind multiple processes to multiple subnets).

> 
> Does what you're trying to do work on an older kernel?  Which kernel
> version does it break at?
> 
> btw. afaik any-ip doesn't work with IPv4 on any un-patched kernel (the
> IPv4 support patch was reverted).


This is actually working with IPv4 (as I said I'm using a recent kernel,
4.1), and the fact that you say it's not supposed to work leads me to
think that maybe we are not talking about the same feature.

Cheers,
	gilberto

Re: [BUG] Any-IP IPv6 support broken

[Maciej Żenczykowski]

> I would like to have a "bind-to-subnet" semantic with IPv6.

Ah, this is something that I have reason to suspect may indeed be
broken for IPv6.
A coworker did some one-off testing on this a few months back, and
didn't get it to trivially work.
We didn't debug it, nor try to figure out what (if anything) was wrong.

Specifically what we were trying to get is a replacement for the
127.0.0.1/8 subnet on lo, ie. more than one IPv6 loopback IP.

> This is currently working with IPv4, and the setup is the follow:
>
> - setup a dummy network device configured with any-IP
> - add an any-IP route
> - bind() on the dummy device

I'm not entirely sure why you have a dummy device.
Couldn't you use 'lo'?  How are you configuring this?
Any-ip routing configuration explicitly uses iif which should never
trigger here.

> in this way we can effectively bind a process to a particular subnet
> (by binding it to a dummy device which is receiving all the packets
> from a particular subnet).

How can a dummy device receive packets?

> The point of using dummy devices is that we can configure multiple ones
> (and so we can bind multiple processes to multiple subnets).

Interesting, I had no idea something like this was possible.
I'm not convinced this is even working as intended.

Naively I'd expect dummy devices to never be the source of packets,
and thus binding to a dummy device to cause a socket to not receive
any traffic.  But obviously I must be wrong.

> This is actually working with IPv4 (as I said I'm using a recent kernel,
> 4.1), and the fact that you say it's not supposed to work leads me to
> think that maybe we are not talking about the same feature.

Yeah, certainly seems like it.

Re: [BUG] Any-IP IPv6 support broken

[Hannes Frederic Sowa]

Hello,

On Thu, Oct 29, 2015, at 16:00, Gilberto Bertin wrote:
> 2- note that it's not actually working with IPv6 addresses:
> 
> # ip -6 route add local abcd:abcd:abcd:abcd::/64 dev eth0


Try the loopback interface:

ip -6 route add local abcd:abcd:abcd:abcd::/64 dev *lo*

Otherwise packets should end up in neighbor subsystem and you don't want
that, still. ;)

Bye,
Hannes

Re: [BUG] Any-IP IPv6 support broken

[Gilberto Bertin]

> On 29 Oct 2015, at 18:39, Hannes Frederic Sowa <hannes@stressinduktion.org> wrote:
> 
> Try the loopback interface:
> 
> ip -6 route add local abcd:abcd:abcd:abcd::/64 dev *lo*
> 
> Otherwise packets should end up in neighbor subsystem and you don't want
> that, still. ;)
> 

Thanks for the reply.

I know it’s working on the lo interface, but unluckily I need it on
other interfaces (and aliasing lo is not an option).

Moreover:
- the IPv6 patch explicitly refers to the possibility to do this with
  eth0 interface (i.e. it's not a lo-only feature)
- should it be consistent with the IPv4 behaviour? (or maybe it's not
  supposed to work even with IPv4 addresses, and so this is a bug)


thank you,

Gilberto.

Re: [BUG] Any-IP IPv6 support broken

[Hannes Frederic Sowa]

On Thu, Oct 29, 2015, at 19:58, Gilberto Bertin wrote:
> 
> > On 29 Oct 2015, at 18:39, Hannes Frederic Sowa <hannes@stressinduktion.org> wrote:
> > 
> > Try the loopback interface:
> > 
> > ip -6 route add local abcd:abcd:abcd:abcd::/64 dev *lo*
> > 
> > Otherwise packets should end up in neighbor subsystem and you don't want
> > that, still. ;)
> > 
> 
> Thanks for the reply.
> 
> I know it’s working on the lo interface, but unluckily I need it on
> other interfaces (and aliasing lo is not an option).
> 
> Moreover:
> - the IPv6 patch explicitly refers to the possibility to do this with
>   eth0 interface (i.e. it's not a lo-only feature)
> - should it be consistent with the IPv4 behaviour? (or maybe it's not
>   supposed to work even with IPv4 addresses, and so this is a bug)

The routing commands won't automatically enable the ndisc layer to
answer neighbour discovery requests for that. The rule thing should work
but your clients somehow need to route all packets over the box with the
"anyip" route setup.

Bye,
Hannes