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

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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

Thanks a lot.
Zhu Yanjun

Add the maintainer of bridge.

Any reply is appreciated.

Zhu Yanjun

On 02/13/2015 05:57 PM, yzhu1 wrote:

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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

Thanks a lot.
Zhu Yanjun
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On Fri, 13 Feb 2015 17:57:45 +0800
yzhu1 [off-list ref] wrote:

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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.

Hi Stephen,
  When we up a bridge without sub-interfaces,  it has "RUNNING" flag as below. Is it correct or not?

1. brctl addbr br0
2. ifconfig br0 up
3. ifconfig br0 
br0 Link encap:Ethernet HWaddr e6:6c:84:a6:fc:64 
          inet6 addr: fe80::e46c:84ff:fea6:fc64/64 Scope:Link 
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:2 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B) TX bytes:168 (168.0 B)

Best Regards
Kuaikuai Wu

-----Original Message-----
From: Stephen Hemminger [mailto:stephen@networkplumber.org] 
Sent: Saturday, February 14, 2015 2:31 AM
To: Zhu, Yanjun
Cc: netdev; Wu, Kuaikuai; Tao, Yue
Subject: Re: If bridge have no sub-interfaces, it's status may be still with 'RUNNING'

On Fri, 13 Feb 2015 17:57:45 +0800
yzhu1 [off-list ref] wrote:

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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.

Hi, Stephen

Follow your advice, I made a new patch. This patch will turn off
carrier when a new bridge interface is created. Please comment on it.

Thanks a lot.
Zhu Yanjun
On 02/14/2015 02:30 AM, Stephen Hemminger wrote:

On Fri, 13 Feb 2015 17:57:45 +0800
yzhu1 [off-list ref] wrote:

quoted

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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.

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

quoted

quoted

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.

quoted

quoted

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

Originally bridge code would start with carrier off,
but there were users using bridge as a form of dummy device
and this broke them. Therefore it was decided (like 5 yrs ago),
that bridge should start with carrier on.

On Mon, 16 Feb 2015 12:55:47 +0800
yzhu1 [off-list ref] wrote:

Hi, Stephen

Follow your advice, I made a new patch. This patch will turn off
carrier when a new bridge interface is created. Please comment on it.

Thanks a lot.
Zhu Yanjun

NAK.
We need to keep the current behavior to not break corner case users.

Hi, all

We should make it compatible. So I made a patch to turn on carrier on this bridge interface when the last sub interface is removed.

Hi, David

Please make tests with this latest patch. Thanks a lot.

Best Regards!
Zhu Yanjun
________________________________________
From: Stephen Hemminger [stephen@networkplumber.org]
Sent: Monday, February 16, 2015 8:51 AM
To: David Ahern
Cc: Zhu, Yanjun; netdev; Wu, Kuaikuai; Tao, Yue
Subject: Re: If bridge have no sub-interfaces, it's status may be still with 'RUNNING'

Originally bridge code would start with carrier off,
but there were users using bridge as a form of dummy device
and this broke them. Therefore it was decided (like 5 yrs ago),
that bridge should start with carrier on.

Hi, Stephen && David

Any update?

Zhu Yanjun

On 02/18/2015 12:14 AM, Zhu, Yanjun wrote:

Hi, all

We should make it compatible. So I made a patch to turn on carrier on this bridge interface when the last sub interface is removed.

Hi, David

Please make tests with this latest patch. Thanks a lot.

Best Regards!
Zhu Yanjun
________________________________________
From: Stephen Hemminger [stephen@networkplumber.org]
Sent: Monday, February 16, 2015 8:51 AM
To: David Ahern
Cc: Zhu, Yanjun; netdev; Wu, Kuaikuai; Tao, Yue
Subject: Re: If bridge have no sub-interfaces, it's status may be still with 'RUNNING'

Originally bridge code would start with carrier off,
but there were users using bridge as a form of dummy device
and this broke them. Therefore it was decided (like 5 yrs ago),
that bridge should start with carrier on.

On 2/24/15 7:55 PM, yzhu1 wrote:

Hi, Stephen && David

Any update?

As I mentioned in my last response I see no problem with the existing behavior -- 3.18, 3.19 and 4.0-rc1. With all of them the bridge stays in the running state after all interfaces are removed.

David

On 02/25/2015 12:23 PM, David Ahern wrote:

On 2/24/15 7:55 PM, yzhu1 wrote:

quoted

Hi, Stephen && David

Any update?

As I mentioned in my last response I see no problem with the existing behavior -- 3.18, 3.19 and 4.0-rc1. With all of them the bridge stays in the running state after all interfaces are removed.

David

Hi, David

I made tests on kernel 3.19-rc7.

1. brctl addbr br0

2. ifconfig br0 up

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

br0       Link encap:Ethernet  HWaddr 0a:70:0b:06:34:8f
          inet6 addr: fe80::870:bff:fe06:348f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:5054 (5.0 KB)

4. brctl addif br0 eth1

5. brctl delif br0 eth1

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

br0       Link encap:Ethernet  HWaddr 00:00:00:00:00:00
          inet6 addr: fe80::870:bff:fe06:348f/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:328 errors:0 dropped:5 overruns:0 frame:0
          TX packets:19 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:39997 (39.9 KB)  TX bytes:5760 (5.7 KB)

Please compare with the outputs of step 3 and step 6, we can find the difference.

uname:

Linux wind-virtual-machine 3.19.0-rc7 #2 SMP Wed Jan 28 18:36:44 CST 2015 x86_64 x86_64 x86_64 GNU/Linux

So I think we should apply the latest patch to make consistent.

3 more lines

Hi, Stephen && David

Any update ?

Best Regards!
Zhu Yanjun
On 02/16/2015 12:55 PM, yzhu1 wrote:

Hi, Stephen

Follow your advice, I made a new patch. This patch will turn off
carrier when a new bridge interface is created. Please comment on it.

Thanks a lot.
Zhu Yanjun
On 02/14/2015 02:30 AM, Stephen Hemminger wrote:

quoted

On Fri, 13 Feb 2015 17:57:45 +0800
yzhu1 [off-list ref] wrote:

quoted

Hi, all

I made this test on ubuntu 14.04 with kernel 3,19-rc7:

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.

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.