Re: If bridge have no sub-interfaces, it's status may be still with 'RUNNING'

On 2/15/15 9:55 PM, yzhu1 wrote:

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1. brctl addbr br0

2. ifconfig br0 up

3. ifconfig br0 (br0's status is with 'RUNNING')

4. brctl addif br0 eth0

5. brctl delif br0 eth0

6. ifconfig br0 (br0's status is without 'RUNNING')

When there is no sub-interface, the flag "RUNNING" is missing after the
last sub-interface is removed.

I do not see that behavior with Fedora 21 and 3.18.5-201.fc21.x86_64. ie., after interface is removed br0 is still in up state. Perhaps a regression with 3.19.

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As such, should we keep "RUNNING" flag after the last sub-interface is
removed?

This is intentional. If there are no active ports in bridge, then
we want to tell applications that packets will go nowhere.

It changes current behavior with respect to tcpdump. Today I can launch tcpdump on a bridge interface before starting a VM. With this change I will not be able to do that.

David