[ovs-discuss] OVS doesn't detach LACP port immediately when link down

[Dan Constantinescu]

* The Open vSwitch version number (as output by "ovs-vswitchd --version").

ovs-vswitchd (Open vSwitch) 1.2.2
Compiled Oct 18 2011 19:28:29
OpenFlow versions 0x1:0x1


* Upstream switch

Cisco Nexus 7000


* What you did that make the problem appear.

- configured OVS with LACP bonding:
ovs-vsctl add-bond br0 bond0 eth0 eth1 bond-mode=balance-tcp lacp=passive other_config:lacp-time=slow

- turn an interface down (either at switch or server side):
ifconfig eth0 down

- verify the link is reported down by the OS:
ethtool eth0
Settings for eth0:
        [...]
        Link detected: no


* What you expected to happen.

If the status of a physical link is down, no matter what LACP timeout value I select, that port should be disabled and removed from the Link Aggregation group immediately.


* What actually happened.

- the port is not detached immediately as reported by ovs-appctl lacp/show bond0
- server keeps trying to send packets over eth0 data path
- eth0 is eventually detached after LACP timeout kicks-in, which is about 90 seconds later.
- the problem is mitigated by using lacp-time=fast, but this is not an option in our case because we lose Cisco ISSU support.


* The kernel version on which Open vSwitch is running

Linux version 3.0.0-12-server (buildd at crested) (gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3) )
Ubuntu 11.10


* The output of "ovs-dpctl show".

# ovs-dpctl show
system at br0:
        lookups: frags:0, hit:1463478513, missed:1213642, lost:852
        port 0: br0 (internal)
        port 1: eth1
        port 2: eth0
        port 3: br112 (internal)
       port 95: tap3a0
        port 96: tap3t1
        port 97: tap4a0
        port 98: tap4t1
        port 112: vnet0
        port 113: vnet1
        port 114: vnet2
        port 115: vnet3
        port 116: vnet4
        port 117: vnet5
        port 118: vnet6
        port 119: vnet7
        port 120: vnet8
        port 121: vnet9
        port 122: vnet10
        port 123: vnet11
        port 124: vnet12
        port 125: vnet13
        port 126: vnet14
        port 127: vnet15
        port 128: vnet16
        port 129: vnet17
        port 130: vnet18
        port 131: vnet19


* A fix or workaround, if you have one.

The problem is mitigated by using lacp-time=fast, but this is not an option in our case because we lose switch ISSU support.


* Any other information that you think might be relevant.

I tried either miimon or carrier for other_config:bond-detect-mode with the same result. It seems that the OVS link detection will only kick-in when lacp-time expires which is not what the LACP timeout is meant for.




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