0 Replies Latest reply on Sep 26, 2018 1:44 AM by sofia_b

    sending order of 'segmented' UDP packets



      when creating an UDP packet, I need to use two mbufs - one containing the UDP header (hdr) and another holding the payload (pay):


      struct rte_mbuf* hdr = rte_pktmbuf_alloc(hdrmp);

      struct rte_mbuf* pay = rte_pktmbuf_alloc(paymp);


      // filling ether, IP, UDP header


      ip_hdr->version_ihl = 0x40 | 0x05; // (*) without 0x05 order it ok



      // setting sizes and linkage

      hdr->data_len   = sizeof(struct ether_hdr) + sizeof(struct ipv4_hdr) + sizeof(struct udp_hdr);

      pay->data_len   = payloadSize;


      hdr->pkt_len    = hdr->data_len + pay->data_len;

      pay->pkt_len    = hdr->pkt_len;


      hdr->next       = pay;

      hdr->nb_segs    = 2;


      When sending plenty of such UDP packets using rte_eth_tx_burst(), all of them were sent correctly, but the sending order seems to be random. When using just a single mbuf for an UDP packet, the sending order is always the order of the packets in the tx array - which is what I expect. Using the header-payload-separation approach and omitting the IP header size info in the ip_hdr field - resulting in a wrong IP packet - the sending order gets ok.

      I'm using the mlx5 PMD, NIC is a ConnectX-5. Could it be some offload mechanisms, influencing the sending order? Maybe someone can help.


      Thanks and best regards

      Sofia Baran