My responses are inline.

Thank you,
Marcus Padgett
Sr Engineer - Service Architecture | Windstream

From: Gregory Rose [mailto:[email protected]]
Sent: Friday, May 18, 2018 5:55 PM
To: Padgett, Marcus <[email protected]>; [email protected]
Subject: Re: [ovs-discuss] OVS VXLAN local_ip does not seem to function - Bug


Hi Marcus,

I have a couple questions inline below...

On 4/26/2018 6:17 AM, Padgett, Marcus wrote:
I have an issue with OVS VXLAN and using the local_ip option for the interface. 
 Some of the IP addresses have been changed in the email since I don't know 
exactly who sees this.

What you did that make the problem appear.
Using a server with two interfaces with two default routes, I want to build a 
VXLAN tunnel over each link to a destination switch.

They both go the same switch?  Is it a real switch or a SW switch like OVS? 
[MP] - They do both go to the same switch (single interface).  Could be either 
hardware or SW switch long term, but right now I'm terminating them to another 
OVS bridge.


  I am utilizing iptables to mark and ip rules to re-direct the traffic for the 
second tunnel out the correct interface.  I have built the VXLAN tunnel in OVS 
trying to use the "local_ip" option.

Please provide the iptables and ip rules you used to redirect the traffic. [MP] 
- Iptables and ip rules below;
ip route add default via $WAN1_GW dev wan1 src $WAN1_IP table wan1
ip route add default via $WAN2_GW dev wan2 src $WAN2_IP table wan2
iptables -t mangle -A OUTPUT -p udp --dport 4789 -s $WAN1_IP -j MARK --set-mark 
0xa1
iptables -t mangle -A OUTPUT -p udp --dport 4789 -s $WAN2_IP -j MARK --set-mark 
0xa2
ip rule add table local priority 10
ip rule del table local priority 0
ip rule add fwmark 0xa1 table wan1 priority 0
ip rule add fwmark 0xa2 table wan2 priority 0

So, I'm trying to capture the packet as it's generated by the process and add a 
MARK, prior to any routing decisions being made (OUTPUT chain in MANGLE table). 
 What I'm seeing (and my assumption) is that the VXLAN packet is generating its 
source IP address based on the local or main routing table while still being 
handled by some OVS process.  I can use the same setup with GRE (change the 
protocol type and remote destination port) and it works as expected.

I set something up similar to this situation and didn't see a problem but I 
wasn't using a real switch.
Also, did you ever have a chance to try out a new version of OVS?  As Ben 
mentioned 2.5.2 is pretty old. [MP] - Yes.  I was able to try this in 2.5.2, 
2.5.4, 2.6.1, and 2.9.1.  All seemed to have the same issue.

Thanks,

- Greg


EXAMPLE:
sudo ovs-vsctl add-port ovs-br1 tun1 -- set Interface tun1 type=vxlan 
options:remote_ip=172.17.253.1 options:key=testflow2 
options:local_ip=172.16.253.16

What you expected to happen.
            I expected the VXLAN tunnel to be sent using the specified source 
IP address of 172.16.253.16 out the correct interface.

What actually happened.
            The VXLAN tunnel exits the correct interface based on my routing 
rules, however was formed utilizing the other interface's IP address 
(172.16.252.108).
            EXAMPLE:
08:24:42.779236 IP 172.16.252.108.57418 > 172.17.253.1.4789: VXLAN, flags [I] 
(0x08), vni 0
LLDP, length 79
08:24:42.779437 IP 172.16.252.108.34566 > 172.17.253.1.4789: VXLAN, flags [I] 
(0x08), vni 0
02:eb:86:0d:38:74 (oui Unknown) > Broadcast, ethertype Unknown (0x8942), length 
93:
        0x0000:  0207 0486 e5fb d3da 4204 0502 0000 000e  ........B.......
        0x0010:  0602 0078 fe12 a423 0501 4f4e 4f53 2044  ...x...#..ONOS.D
        0x0020:  6973 636f 7665 7279 fe17 a423 0502 6f66  iscovery...#..of
        0x0030:  3a30 3030 3038 3665 3566 6264 3364 6134  :000086e5fbd3da4
        0x0040:  3208 0a75 6370 652d 7475 6e2d 3200 00    2..tun1..

The Open vSwitch version number (as output by ovs-vswitchd --version).
ovs-vswitchd (Open vSwitch) 2.5.2
Compiled Oct 17 2017 16:38:57

The kernel version on which Open vSwitch is running (from /proc/version) and 
the distribution and version number of your OS (e.g. "Centos 5.0").
            Linux version 4.4.0-87-generic (buildd@lcy01-31) (gcc version 5.4.0 
20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #110-Ubuntu SMP Tue Jul 18 12:55:35 
UTC 2017

The output of ovs-dpctl show.
system@ovs-system:
        lookups: hit:191881 missed:5814 lost:0
        flows: 4
        masks: hit:471168 total:4 hit/pkt:2.38
        port 0: ovs-system (internal)
        port 1: ovs-br1 (internal)
        port 2: vxlan_sys_4789 (vxlan)
        port 3: ovs-lan (internal)
        port 4: k8s-br (internal)
        port 5: mirror-br (internal)
        port 6: ens6
        port 7: wan2 (internal)

Any other information that you think might be relevant.
Everything works fine when building with GRE instead of VXLAN, all the same 
routing and firewall rules.  The rules are not matching any protocol specific 
parameters, just matching on destination IP address to mark the traffic.

Thank you,
Marcus Padgett
Sr Engineer - Service Architecture | Windstream
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