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DevStack: DHCP packets not received by q-dhcp

asked 2015-11-13 01:09:25 -0500

stier gravatar image

Hi,

in setting up DevStack with Neutron networking on a XenServer 6.2 Hypervisor I have encountered the following problem: DHCP requests by my VMs make it to the device on the same bridge as my DHCP's virtual device, but I cannot see them within the network space of my DHCP server.

I would greatly appreciate any pointers. Thanks!

root@DevStackOSDomU:/opt/stack/devstack# ovs-vsctl show
41724651-26ec-448b-8e67-e29d70dff8db
    Bridge br-ex
        Port br-ex
            Interface br-ex
                type: internal
        Port phy-br-ex
            Interface phy-br-ex
                type: patch
                options: {peer=int-br-ex}
        Port "tape8d3176c-c2"
            Interface "tape8d3176c-c2"
                type: internal
        Port "qg-19bdd2c0-81"
            Interface "qg-19bdd2c0-81"
                type: internal
    Bridge "xapi5"
        fail_mode: secure
        Port int-br-ex
            Interface int-br-ex
                type: patch
                options: {peer=phy-br-ex}
        Port "int-br-eth1"
            Interface "int-br-eth1"
                type: patch
                options: {peer="phy-br-eth1"}
        Port "xapi5"
            Interface "xapi5"
                type: internal
        Port "phy-xapi5"
            Interface "phy-xapi5"
                type: patch
                options: {peer="int-xapi5"}
        Port "int-xapi5"
            Interface "int-xapi5"
                type: patch
                options: {peer="phy-xapi5"}
        Port int-br-int
            Interface int-br-int
                type: patch
                options: {peer=phy-br-int}
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
    Bridge br-tun
        fail_mode: secure
        Port br-tun
            Interface br-tun
                type: internal
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
    Bridge "br-eth1"
        Port "br-eth1"
            Interface "br-eth1"
                type: internal
        Port "br-eth1-br-int"
            Interface "br-eth1-br-int"
                type: patch
                options: {peer="br-int-br-eth1"}
        Port "eth1"
            Interface "eth1"
        Port "phy-br-eth1"
            Interface "phy-br-eth1"
                type: patch
                options: {peer="int-br-eth1"}
    Bridge br-int
        fail_mode: secure
        Port br-int
            Interface br-int
                type: internal
        Port "tap46853718-81"
            tag: 4095
            Interface "tap46853718-81"
                type: internal
        Port "tap418a711d-1d"
            tag: 4095
            Interface "tap418a711d-1d"
                type: internal
        Port "br-int-br-eth1"
            Interface "br-int-br-eth1"
                type: patch
                options: {peer="br-eth1-br-int"}
        Port "tap3347a71c-1d"
            tag: 4095
            Interface "tap3347a71c-1d"
                type: internal
        Port phy-br-int
            Interface phy-br-int
                type: patch
                options: {peer=int-br-int}
        Port "qr-de58b4e5-70"
            tag: 4095
            Interface "qr-de58b4e5-70"
                type: internal
        Port "qr-c27b1b61-b9"
            tag: 4095
            Interface "qr-c27b1b61-b9"
                type: internal
        Port "qr-1aa89005-9e"
            tag: 4095
            Interface "qr-1aa89005-9e"
                type: internal
    ovs_version: "2.0.2"

ovs-ofctl:

root@DevStackOSDomU:/opt/stack/devstack# ovs-ofctl dump-flows br-int
NXST_FLOW reply (xid=0x4):
 cookie=0xacdca3c11f0fcef9, duration=2677.245s, table=0, n_packets=84, n_bytes=3528, idle_age=1858, priority=2,in_port=5 actions=drop
 cookie=0xacdca3c11f0fcef9, duration=2678.533s, table=0, n_packets=0, n_bytes=0, idle_age=2678, priority=2,in_port=11 actions=drop
 cookie=0xacdca3c11f0fcef9, duration=2678.812s, table=0, n_packets=547, n_bytes=85401, idle_age=0, priority=0 actions=NORMAL
 cookie=0xacdca3c11f0fcef9, duration=2678.793s, table=23, n_packets=0, n_bytes=0, idle_age=2678, priority=0 actions=drop
 cookie=0xacdca3c11f0fcef9, duration=2678.775s, table=24, n_packets=0, n_bytes=0, idle_age=2678, priority=0 actions=drop

tcpdump on br-int

root@DevStackOSDomU:/opt/stack/devstack# tcpdump -i br-int
tcpdump: WARNING: br-int: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on br-int, link-type EN10MB (Ethernet), capture size 65535 bytes
13:48:25.158972 IP6 fe80::f816:3eff:fec7:dad9 > ff02::1: ICMP6, router advertisement, length 56
13:48:29.671225 IP6 fe80::f816:3eff:fec7:dad9 > ff02::1: ICMP6, router advertisement, length 56
13:48:30.439155 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:6c:a3:4d (oui Unknown), length 280
13:48:33.441836 IP ...
(more)
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answered 2015-11-13 08:28:49 -0500

stier gravatar image

updated 2015-11-15 04:31:55 -0500

Found the solution. I followed the following steps:

fix ml2_conf.ini and ml2_conf.inidomU, c.f. end of https://www.citrix.com/blogs/2015/10/13/xenserver-debugging-on-vmscannot-get-ip-from-dhcp-agent/ (https://www.citrix.com/blogs/2015/10/...)

  1. insert patch between the bridges br-eth1 and br-int
  2. Killed a rampant dnsmasq process: fuser -k dnsmasq
  3. Restarted q-dhcp
  4. Removed vlan tag
  5. LAN tag in Port of q-dhcp: ovs-vsctl remove port tap15b7c4e4-a0 tag 4095
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Asked: 2015-11-12 15:55:19 -0500

Seen: 110 times

Last updated: Nov 15 '15