netdev - Re: [Qemu-devel] macvlan/macvtap: guest/host cannot communicate when network cable is unplugged

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Date:	Thu, 30 Aug 2012 13:53:28 +0100
From:	Stefan Hajnoczi <stefanha@...il.com>
To:	ching <lsching17@...il.com>
Cc:	qemu-devel@...gnu.org, kaber@...sh.net,
	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org
Subject: Re: [Qemu-devel] macvlan/macvtap: guest/host cannot communicate when
 network cable is unplugged

On Thu, Aug 30, 2012 at 1:13 PM, ching <lsching17@...il.com> wrote:
>
>> Can you try the same test with two macvlan interfaces on the host (no
>> macvtap)?  You may need to use the ping -I <interface-address>
>> argument to force the ping source address to a specific macvlan
>> interface.
>>
>> If you see the same problem, it may just be the macvlan design - it is
>> stacked on top of eth0 and might not work when eth0 is down.  CCing
>> macvlan/macvtap folks.
>>
>> Stefan
>>
>
> tested as below
>
> $ifconfig
>
>     eth0      Link encap:Ethernet  HWaddr f4:6d:xx:xx:xx:xx
>               inet6 addr: fe80::xx:xx:xx:xx/64 Scope:Link
>               UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>               RX packets:86507 errors:0 dropped:0 overruns:0 frame:0
>               TX packets:55940 errors:0 dropped:0 overruns:0 carrier:0
>               collisions:0 txqueuelen:1000
>               RX bytes:126005746 (120.1 MiB)  TX bytes:4394225 (4.1 MiB)
>
>     macvtap0  Link encap:Ethernet  HWaddr 52:54:xx:xx:xx:xx
>               inet6 addr: fe80::xx:xx:xx:xx/64 Scope:Link
>               UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>               RX packets:70 errors:0 dropped:0 overruns:0 frame:0
>               TX packets:84 errors:0 dropped:0 overruns:0 carrier:0
>               collisions:0 txqueuelen:500
>               RX bytes:9036 (8.8 KiB)  TX bytes:14734 (14.3 KiB)
>
>     znet0     Link encap:Ethernet  HWaddr 00:60:xx:xx:xx:92
>               inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
>               inet6 addr: 2002:xx:xx:xx:xx/64 Scope:Global
>               inet6 addr: fe80:xx:xx:xx:xx/64 Scope:Link
>               UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>               RX packets:4463190 errors:0 dropped:0 overruns:0 frame:0
>               TX packets:12527522 errors:0 dropped:0 overruns:0 carrier:0
>               collisions:0 txqueuelen:0
>               RX bytes:3959213697 (3.6 GiB)  TX bytes:18590336476 (17.3 GiB)
>
>    znet1     Link encap:Ethernet  HWaddr 00:60:xx:xx:xx:99
>               inet addr:192.168.1.177  Bcast:192.168.1.255  Mask:255.255.255.0
>               inet6 addr: 2002:xx:xx:xx:xx64 Scope:Global
>               inet6 addr: fe80:xx:xx:xx:xx/64 Scope:Link
>               UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>               RX packets:8 errors:0 dropped:0 overruns:0 frame:0
>               TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
>               collisions:0 txqueuelen:0
>               RX bytes:1399 (1.3 KiB)  TX bytes:1522 (1.4 KiB)
>
> $ ip -d link show
>
>     10: znet0@...0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
>         link/ether 00:60:xx:xx:xx:92 brd ff:ff:ff:ff:ff:ff
>         macvlan  mode bridge
>     15: znet1@...0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT
>         link/ether 00:60:xx:xx:xx:99 brd ff:ff:ff:ff:ff:ff
>         macvlan  mode bridge
>
>
> the macvlan interface cannot ping each other no matter network cable is plugged or not
>
> $ ping -I 192.168.1.2 192.168.1.177
> PING 192.168.1.177 (192.168.1.177) from 192.168.1.2 : 56(84) bytes of data.
>
> --- 192.168.1.177 ping statistics ---
> 6 packets transmitted, 0 received, 100% packet loss, time 4999ms

In bridge mode I expected them to be able to communicate.

> I also perform an additional test: the guests (macvtap bridge mode) CAN communicate each other no matter network cable is plugged or not.

Strange.  I thought the original problem was that the macvtap guests
cannot communicate with each other when the network cable is
unplugged?

Hopefully someone else can help you, I'm not familiar enough with
macvlan/macvtap.

Stefan
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