[ovs-discuss] Help in understanding the code

Andy Zhou azhou at nicira.com
Wed Jul 10 14:38:10 UTC 2013


The remaining icmp packets are indeed processed in the kernel (via
ovs_dp_process_received_packet()). ovs-vswitchd will install a flow entry
in the kernel to handle those packets.
You can inspect kernel flows with "ovs-dpctl dump-flows".

VLOG_INFO is only for user space programs. I am surprised it compiled with
kernel module. printk may work better.

--andy


On Wed, Jul 10, 2013 at 4:20 AM, sujith p s <sujithpandels at gmail.com> wrote:

> Hi everyone!
> I'm a newcomer to OpenvSwitch. I installed it in mininet-VM using the
> INSTALL guide provided.
> I am curious to understand the flow of the code in case of ping.
>
> Example topology:
> $ sudo mn --switch=ovsk --topo linear
>
>  h1 -- s1 -- s2 -- h2
>
> command:
> mininet> h1 ping -c5 h2
>
> ofproto_run recognises a new flow ( 1st ping packet - icmp echo from h1 to
> h2 ) and send it as PACKET_IN to the controller.
> Controller sends back the respective FLOW_MOD back to switch s1.
> handle_openflow() function takes care of these things.
> Similarly above 2 steps happens for icmp echo reply from h2 to h1.
>
> Now, I understand that since flow_mods are already installed in the flow
> table, there's no need to contact the controller once again for the 2nd
> icmp-echo packet from h1 to h2.
>
> What I wanted to know is which module(s) manages the remaining icmp
> packets, i.e. checking for a match and do the forwarding of these packets
> through mentioned port of the switch.
>
> It looks like ovs_dp_process_received_packet() in datapath.c So I tried
> checking by inserting VLOG_INFO statements in the module and installed it
> again. Looks like I was wrong about that.
>
> I wanted to make sure that I am in the correct path.
>
> Can anyone help me please!
>
> Thanks in advance
> Sujith
>
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>
>
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