Hello, I’m having problems with sending custom packets using the ofproto_dpif_send_packet(). As said in the previoius thread https://mail.openvswitch.org/pipermail/ovs-discuss/2020-June/050204.html I thought to have correctly created a custom udp packet that contains as a payload a buffer of dp_packets this is the code:
struct my_captured_packet { struct dp_packet packet; int sizeofpayload; }; static struct my_captured_packet dp_packet_buff1[PACKET_BUFF_ELEMENTS]; //function to copy incoming packets to dp_packet_buff1 //….. //function part to send the buffer of packets as payload of new udp packet struct dp_packet *packetAggr; packetAggr = dp_packet_new(65535); struct flow flow; //extract a flow from a buffed pkt flow_extract(&dp_packet_buff1[0].packet, &flow); //use the flow to build a new packet flow_compose(packetAggr, &flow, NULL, 0); //copy buffer as udp payload memcpy((char *) dp_packet_l4(packetAggr) + UDP_HEADER_LEN, dp_packet_buff1, sizeof(dp_packet_buff1)); //Then I reversed the procedure to see if I could extract the single packets from the payload of my custom packet //struct my_captured_packet *recvdpackets = (struct my_captured_packet *) dp_packet_get_udp_payload(packetAggr); //print dp_packet payloads extracted for(int j=0; j<PACKET_BUFF_ELEMENTS; j++) { VLOG_ERR("payload #%d: %.*s with size of packet %d", j, recvdpackets[j].sizeofpayload, (char *) dp_packet_get_udp_payload(&recvdpackets[j].packet), (int) dp_packet_size(&recvdpackets[j].packet) ); } const struct ofproto_dpif *ofproto = ctx->xin->ofproto; const struct ofport_dpif *portAggr; ofp_port_t out_port = 2; portAggr = ofp_port_to_ofport(ofproto, out_port); ofproto_dpif_send_packet(portAggr, false, packetAggr); The above code works as intended, meaning after creating packetAggr and setting its payload to dp_packet_buff1 I can cast it back to its original type after retrieving it with dp_packet_get_udp_payload, and print the single packets. However after I send this packet and do this same exact procedure as part of a new action that is intended to just extract the payload and single packets, the cast to struct my_captured_packet * doesn’t seem to work. The following is what gets printed on GDB: //upon packet arrival, check the mac to see if it’s the packet intended for extraction //print the packet packet_recvd = dp_packet_clone (ctx->xin->packet); VLOG_ERR("structure of pkt received: %s ", ofp_dp_packet_to_string(packet_recvd)) Gdb --> structure of pkt received by deaggr: udp,vlan_tci=0x0000,dl_src=00:00:00:00:00:01,dl_dst=00:00:00:00:00:02,nw_src=10.0.0.1,nw_dst=10.0.0.2,nw_tos=0,nw_ecn=0,nw_ttl=64,tp_src=47981,tp_dst=444 udp_csum:2eb2 //Extract the payload by casting struct my_captured_packet *checkrecvd = (struct my_captured_packet *) dp_packet_get_udp_payload(packet_recvd); VLOG_ERR("structure of first packet extracted from buffer: %s with size_ of %d", ofp_dp_packet_to_string(&checkrecvdAggr[0].packet), checkrecvdAggr[0].packet.size_); Gdb--> structure of first packet extracted from buffer: packet_type=(0x302c,0x646c) //this should be a normal structured dp_packet with size_ of 21299712 //size seems abnormal I’ve tried this whole algorithm by sending a normal packet received without creating a new one and it works, so I’m guessing the problem is still in how I structure my custom packet, so my question is what am I missing in order to create a valid custom UDP packet that is sendable from OVS? Can I find examples anywhere in the codebase? I haven’t seen anything to be honest. Help is really needed! Thanks, Luca
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