8:26 a.m.
On Tue, Mar 12, 2019 at 11:10:40PM +0100, Lars Lindstrom wrote:
Hi everyone!
I have the following requirement: I need to connect a set of Docker
containers to a KVM. The containers shall be isolated in a way that they
cannot communicate to each other without going through the KVM, which
will act as router/firewall. For this, I thought about the following
simple setup (as opposed to a more complex one involving a bridge with
vlan_filtering and a seperate VLAN for each container):
+------------------------------------------------------------------+
| Host |
| +-------------+ +----------------------+---+
| | KVM | | Docker +-> | a |
| | +----------+ +----------+ +--------------+ +---+
| | | NIC lan0 | <-> | DEV tap0 | <-> | NET macvlan0 | <-+-> | b |
| | +----------+ +----------+ +--------------+ +---+
| | | | +-> | c |
| +-------------+ +----------------------+---+
| |
+------------------------------------------------------------------+
NIC lan0:
<interface type='direct'>
<source dev='tap0' mode='vepa'/>
<model type='virtio'/>
</interface>
*** Welcome to pfSense 2.4.4-RELEASE-p1 (amd64) on pfSense ***
LAN (lan) -> vtnet0 -> v4: 10.0.20.1/24
DEV tap0:
[root@server ~]# ip tuntap add tap0 mode tap
[root@server ~]# ip l set tap0 up
[root@server ~]# ip l show tap0
49: tap0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc
fq_codel state DOWN mode DEFAULT group default qlen 1000
link/ether ce:9e:95:89:33:5f brd ff:ff:ff:ff:ff:ff
[root@server ~]# virsh start pfsense
[root@server opt]# ip l show tap0
49: tap0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc
fq_codel state DOWN mode DEFAULT group default qlen 1000
link/ether ce:9e:95:89:33:5f brd ff:ff:ff:ff:ff:ff
IIUC, you are using the tap0 device, but it is not plugged anywhere. By that I
mean there is one end that you created and passed through into the VM, but there
is no other end of that. I can think of some complicated ways how to do what
you are trying to, but hopefully the above explanation will move you forward and
you'll figure out something better than what I'm thinking about right now. What
usually helps me is to think of a way this would be done with hardware and
replicate that as most of the technology is modelled after HW anyway. Or
someone else will have a better idea.
Before sending it I just thought, wouldn't it be possible to just have a veth
pair instead of the tap device? one end would go to the VM and the other one
would be used for the containers' macvtaps...
NET macvlan0:
[root@server ~]# docker network create --driver macvlan
--subnet=10.0.20.0/24 --gateway=10.0.20.1 --opt parent=tap0 macvlan0
CNT a:
[root@server ~]# docker run --network macvlan0 --ip=10.0.20.2 -it
alpine /bin/sh
/ # ping -c 4 10.0.20.1
PING 10.0.20.1 (10.0.20.1): 56 data bytes
--- 10.0.20.1 ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss
/ # ifconfig
eth0 Link encap:Ethernet HWaddr 02:42:0A:00:14:02
inet addr:10.0.20.2 Bcast:10.0.20.255 Mask:255.255.255.0
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:448 (448.0 B) TX bytes:448 (448.0 B)
/ # ip r
default via 10.0.20.1 dev eth0
10.0.20.0/24 dev eth0 scope link src 10.0.20.2
CNT b:
[root@server ~]# docker run --network macvlan0 --ip=10.0.20.2 -it
alpine /bin/ping 10.0.20.1
PING 10.0.20.1 (10.0.20.1): 56 data bytes
CNT c:
[root@server ~]# docker run --network macvlan0 --ip=10.0.20.2 -it
alpine /bin/ping 10.0.20.1
PING 10.0.20.1 (10.0.20.1): 56 data bytes
The KVM is not reachable from within a Docker container (during the test
firewalld was disabled) and vice versa. The first thing I noticed is
that tap0 remains NO-CARRIER and DOWN, even though the KVM has been
started. Shouldn't the link come up as soon as the KVM is started (and
thus is connected to the tap0 device)? The next thing that looked
strange to me - even though interface and routing configuration within
the container seemingly looks OK, there are 0 packets TX/RX on eth0
after pinging the KVM (but 4 on lo instead).
Any idea on how to proceed from here? Is this a valid setup and a valid
libvirt configuration for that setup?
Thanks and br, Lars
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