[ovs-discuss] DP_Packet Payload Modification

Gregory Rose gvrose8192 at gmail.com
Fri Jun 5 21:05:11 UTC 2020


On 6/5/2020 11:00 AM, Luca Mancini wrote:
> 
> Hi Greg,
> I realized I didn’t give a lot of context..
> Basically, I’m implementing a custom action which is meant to buffer an x amount of dp_packets that match a certain flow, and then send a new packet directly from the switch, containing the buffer of packets, as its payload. At some other switch this payload is then meant to be extracted so that I can retrieve the buffer of dp_packets and send the single packets contained in the buffer to the correct hosts.
> My action is implemented in userspace only for now since efficiency isn’t a concern for me atm. I already implemented the buffering mechanism and it works, and now I’m trying to create this custom udp packet so that I can store the buffer in it. For now I’m only trying to create a dummy udp packet with a “hello world” string as its payload just to see if I can create this custom packet however I just can’t figure out what I’m missing. My most recent attempt is the following:
> 
> 1.Extract flow from one of the previously stored dp_packets
> 2.create a new dp_packet with dp_packet_new(65035)
> 3.use flow_compose() function on new packet to create a valid packet
> 4.add payload with dp_packet_put
> 
> Code:
> struct flow flow;
> flow_extract(&dp_packet_buff1[0].packet, &flow);
> flow_compose(packetAggr, &flow, NULL, 0);
> char * payload = "hello world";
> dp_packet_put(packetAggr, payload, sizeof payload);

Pseudo code looks fine but the devil is in all the other details.  I
need to see a patch to put it in context.

- Greg


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