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Old 08-25-2015, 09:52 AM   #1
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Registered: Aug 2015
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Dropping packets on virtual interface

Hi everyone!

I'm working with openvirtualswitch running the following setup:

OVS running in a host computer, this host computer also has 3 VM machines(A_VM,B_VM,C_VM). Said VMs are connected to the OVS using:

ip tuntap add mode tap A_IF
ip link set A_IF promisc on
ip link set A_IF up
ovs-vsctl add-port br1 A_IF

then the A_VM eth1 interface is bridge to A_IF, this is for VM A, others are similar.

Now I want to route all ip traffic from A_VM to C_VM by B_VM, to do so I implement the following rule on the ovs:

OFPST_FLOW reply (OF1.3) (xid=0x2):
cookie=0x0, duration=4049.313s, table=0, n_packets=3943, n_bytes=386246, priority=10,ip,in_port=1 actions=output:2
cookie=0x0, duration=4299.140s, table=0, n_packets=708, n_bytes=60016, priority=1 actions=NORMAL

Where port 1 is A_IF and port 2 is B_IF.

And this is where I'm stuck: B_VM is receiving nothing, although tcpdump in the host B_IF confirms the retransmitted package but tcpdump inside the B_VM sees nothing.

Can you guys help me find the problem?

Kind regards,
Old 08-26-2015, 07:23 PM   #2
Registered: Sep 2004
Location: Japan
Distribution: CentOS 7.1
Posts: 735

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I had a very similar problem recently running pfsense in a virtual machine with bridged interfaces.

The problem was because pfsense tried tcp checksum offloading and it did not work very well with virtio interfaces.

I am not familiar with the virtual switch you are using but if I have to point a finger, check the network interface options especially checksum off loading and other advanced hardware features. Turn them off to test and see what happens.


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