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Devstack w/OpenDaylight: Cirros DHCP not working

asked 2016-01-06 12:42:36 -0700

jwoodlock gravatar image

updated 2016-01-08 18:37:33 -0700

Additional info on this problem: It appears that the DHCP agent interface is in the down state on br-int (along with br-int itself),this then blocks the flow updates. The data is at the bottom of the details section. Can anyone explain why the interface is down? (DHCP process is up) There's a "no such device" message in the ovs-switchd.log (note: The additional data was captured after unstack/stack so the interface names changed; however no changes were made between runs so the problem is identical)

Original issue: I'm using an all-in-one configuration of DevStack w/Lithium and the Cirros VMs do not receive an IP from DHCP. The stack process appears to complete successfully and when the VMs are instantiated they appear to bind to br-int properly. The DHCP process is running and is bound into bri-int as well. Now when I put wireshark on the various taps, I can see the request leave the VM but it never goes on the tap towards the DHCP server. Therefore I believe the problem is in the OpenFlow processing of the broadcast but I'm at a loss as to what to check (or what I missed in the devstack setup)

Here's the openvswitch and the local.conf

[stack@localhost Desktop]$ sudo ovs-vsctl show
    Manager "tcp:"
        is_connected: true
    Bridge br-int
        Controller "tcp:"
            is_connected: true
        fail_mode: secure
        Port "tapb6b82370-c4"
            Interface "tapb6b82370-c4"
        Port br-int
            Interface br-int
                type: internal
        Port patch-ext
            Interface patch-ext
                type: patch
                options: {peer=patch-int}
        Port "tap9ebd858f-2e"
            Interface "tap9ebd858f-2e"
        Port "tap421acffe-e3"
            Interface "tap421acffe-e3"
                type: internal
    Bridge br-ex
        Controller "tcp:"
            is_connected: true
        fail_mode: secure
        Port br-ex
            Interface br-ex
                type: internal
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-ext}
    ovs_version: "2.4.0"


disable_service n-net
disable_service cinder
disable_service swift
enable_service n-cpu
enable_service n-cond
enable_service n-novnc
enable_service q-svc
enable_service q-agt
enable_service q-dhcp
enable_service q-l3
enable_service q-meta
enable_service neutron
enable_service tempest

enable_service odl-server odl-compute 

#enable_plugin networking-odl
enable_plugin networking-odl


Additional info:

[stack@localhost devstack]$ sudo ovs-ofctl show br-int -O openflow13
OFPT_FEATURES_REPLY (OF1.3) (xid=0x2): dpid:0000a2f784af4747
n_tables:254, n_buffers:256
OFPST_PORT_DESC reply (OF1.3) (xid=0x3):
 1(tap19caa118-09): addr:00:00:00:00:00:00  
     config:     PORT_DOWN
     state:      LINK_DOWN
     speed: 0 Mbps now, 0 Mbps max
 2(patch-ext): addr:2e:06:17:41:06:6e
     config:     0
     state:      0
     speed: 0 Mbps now, 0 Mbps max
 LOCAL(br-int): addr:a2:f7:84:af:47:47
     config:     PORT_DOWN
     state:      LINK_DOWN
     speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (OF1.3) (xid=0x5): frags=normal miss_send_len=0

2016-01-08 17:39:53,767 | INFO  | ntDispatcherImpl | GatewayMacResolverService        | 261 ...
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Take a look at flows and their stat counters to determine which flows are being hit. This will help figure out where the pkts are lost in pipeline.

Vishal Thapar ( 2016-01-08 01:45:16 -0700 )edit

I had the same problem and for me the solution was to set the local_ip up, try to use the following command:

ovs-vsctl set Open_vSwitch <your_switch_uuid> other_config:local_ip=<your_data_ip>
, and then check out if you have IP'S now from the DHCP

Gabs90 ( 2016-01-11 00:42:12 -0700 )edit

Your additional output seems to be from a different run/setup, so doesn't help. No sure about PORT_DOWN, I think it is always DOWN for tap ports in a namespace. You mentioned 'no such device' msg in dhcp log, what is the device name giving error?

Vishal Thapar ( 2016-01-12 03:20:35 -0700 )edit

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answered 2016-01-13 15:43:15 -0700

jwoodlock gravatar image

I found the cause of the problem. I don't know if it's coming from OpenStack or OpenDaylight, but the issue is the transaction to setup IPv6 flows for the VM throws exceptions. You can see it in the OpenDaylight client

java.lang.IllegalArgumentException: Supplied value "fd44:f1e1:98ba:0:f816:3eff:fe1e:2738/32" does not match required pattern "^(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]).){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])/(([0-9])|([1-2][0-9])|(3[0-2]))$"

Now the subnet that OpenStack is requesting is the Private one built by default (by devstack) so it has both an IPv4 and IPv6 address to it. Either the request contains both IPv4 and IPv6 and is being processed as only IPv4 by OpenDayLight or the formatting is something OpenDayLight isn't expecting. Either way the transition blows up and the flows are not setup, however the VM is bound into the switch (so it shows success on OpenStack)

I built a completely different subnet for the VM using only IPv4 and it spins up and the DHCP request works

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I use following two settings in my devstack, should be self explanatory: `IP_VERSION=4` `NEUTRON_CREATE_INITIAL_NETWORKS=False`

Vishal Thapar ( 2016-01-14 02:13:49 -0700 )edit

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Asked: 2016-01-06 12:42:36 -0700

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Last updated: Jan 13 '16