How do we can Access to Payload of Received Packets in DPDK 18.11.9

Question

I am running dpdk-stable-18.11.9 on Ubuntu 18.04.I have external card that was generating UDP packet continuously (rate:40Gbps) I want to

Answer 1

In order to access a received packet's ethernet payload use DPDK API rte_pktmbuf_mtod().

    for (i = 0; i < nb_rx; i++) {
        /* access payload of rcv'd pkt at ethernet header */
        eth_hdr = rte_pktmbuf_mtod(pkt, struct ether_hdr *);
    }

but if the intention is more than just ethernet header, you can refer to below sample code snippet for ipv4.

#include <linux/if_vlan.h>

In the main processing loop

uint16_t i, nb_rx, len;
uint16_t ether_type;
struct ether_hdr *eth_hdr;
struct vlan_hdr *vh;
uint16_t *proto;
struct ipv4_hdr *ip_hdr;
struct rte_mbuf *pkts_burst[MAX_PKT_BURST];

/* rcv burst of pkts from interface, on success returns no. of pkts rcv'd  */
nb_rx = rte_eth_rx_burst(port_id, queue_id, pkts_burst, MAX_PKT_BURST)

/* Loop through rcv'd pkts */
for (i = 0; i < nb_rx; i++) {
    /* update len on each iteration to 0 */
    len = 0;

    /* access payload of rcv'd pkt at ethernet header */
    eth_hdr = rte_pktmbuf_mtod(pkts_burst[i], struct ether_hdr *);

    if (rte_cpu_to_be_16(ETHER_TYPE_VLAN) == eth_hdr->ether_type) {
        len = sizeof(struct ether_hdr);
        vh = (struct vlan_hdr *)(eth_hdr + 1);

        proto = vh->eth_proto;
        if (rte_cpu_to_be_16(ETHER_TYPE_VLAN) == *proto) {
            len += sizeof(struct vlan_hdr);
            proto = vh->eth_proto;
        }

         /* free up non ipv4 packets */
         if (rte_cpu_to_be_16(ETHER_TYPE_IPv4) != *proto)
             rte_pktmbuf_free(pkt);
    }

    /* access IP header of rcv'd pkt */
    ip_hdr = (struct ipv4_hdr *)(rte_pktmbuf_mtod(pkts_burst[i], char *) + len);   

    /* process packets which are ipv4 */
}