[dpdk-dev] About the data payload of rte_mbuf?

["bai bakari" <912873551@qq.com>]

Hi,


Now, I want to get the data payload of rte_mbuf, and i wrote the following code:


struct ipv4_hdr *ipv4_hdr;
struct tcp_hdr *tcp_hdr;
uint32_t payload_len, ip_len;
uint8_t *payload = NULL;



ipv4_hdr = rte_pktmbuf_mtod_offset(m, struct ipv4_hdr *, sizeof(struct ether_hdr));
ip_len = ntohs(ipv4_hdr->total_length);



if (ipv4_hdr->next_proto_id == IPPROTO_TCP) {
    tcp_hdr = (struct tcp_hdr *)((uint8_t *)ipv4_hdr + ((ipv4_hdr->version_ihl & 0xf) << 2));
    payload = (uint8_t *)tcp_hdr + (tcp_hdr->data_off << 2);
    payload_len = ip_len - (payload - (uint8_t *)ipv4_hdr);

}


when i send packets using dpdk-pktgen, i found:
ip_len = 46
ip_header_len = 20
but the tcp_header_len=(tcp_hdr->data_off << 2)=0, 
and (payload - (uint8_t *)ipv4_hdr) = 340 > ip_len.


I'm confused, is there any errors about the code to compute the payload_len of rte_mbuf? 
I think maybe the dpdk-pktgen cannot send the packets with payload? 


I'm a beginner, anyone can help me how to compute the payload_len of rte_mbuf and test it?


Thank you in advance!