[systemd-devel] systemd-networkd bridge doesn't work until switched to promiscous mode

[Elias Probst]

On 02/11/2015 07:34 PM, Lennart Poettering wrote:
> On Wed, 11.02.15 17:48, Peter Lemenkov (lemenkov at gmail.com) wrote:
> 
>> Hello All!
>> I see that promiscous mode was discussed a few times before but I'm
>> not sure if I found something new or not.
>>
>> I've got the following setup - a physical interface (enp1s0f0), which
>> I wanted to add to the bridge (br0).
>>
>> My setup consists of the following files
>>
>> * br0.netdev:
>>
>> [NetDev]
>> Name=br0
>> Kind=bridge
>>
>> * br0.network:
>>
>> [Match]
>> Name=br0
>>
>> [Network]
>> Address=xx.yy.zz.27/27
>> Gateway=xx.yy.zz.17
>>
>> * enp1s0f0.network:
>>
>> [Match]
>> Name=enp1s0f0
>>
>> [Network]
>> Bridge=br0
>>
>> So this looks pretty simple. Unfortunately it doesn't work.
>>
>> If I start pinging xx.yy.zz.17, then I see (using tcpdump) that the
>> gateway even replies, and this reply was received at physical
>> interface but br0 doesn't recognize it (and consequently ping didn't
>> get a reply back).
>>
>> But if I change the br0 mode with "ifconfig br0 promisc" it starts
>> receiving data.
>>
>> Is this a known issue? Or maybe I missed something in docs?
> 
> Sounds like a kernel bug. Normally the bridge logic should turn on
> promisc mode automatically if this is needed. If this doesn't work
> this appears to be a kernel bug. 
> 
> That said, Tom might know more. Tom?

Any updates on this?
Any idea who's really to blame for that? Kernel? systemd-networkd?

Seeing exactly the same issue on CentOS 7 here with a really simple
bridge setup which looks more or less the same as the one above.

It can be worked around temporarily (until the next reboot) using
ip link set dev vmbridge promisc on

Is there a better/cleaner way to permanently work around it? Couldn't
find a way to set something like "Promisc=On" in a bridge's .netdev

Using systemd-219 from https://copr.fedoraproject.org/coprs/lnykryn/systemd/
CentOS 7 runs Kernel 3.10.0-123.el7.x86_64

- Elias

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://lists.freedesktop.org/archives/systemd-devel/attachments/20150325/052e83ae/attachment.sig>