[dpdk-dev] 回复: About the data payload of rte_mbuf?
bai bakari
912873551 at qq.com
Thu Dec 6 07:19:50 CET 2018
Thank your answers, that helped me out.
------------------ 原始邮件 ------------------
发件人: "Shyam Shrivastav"<shrivastav.shyam at gmail.com>;
发送时间: 2018年12月6日(星期四) 下午2:22
收件人: "bai bakari"<912873551 at qq.com>;
抄送: "dev"<dev at dpdk.org>;
主题: Re: [dpdk-dev] About the data payload of rte_mbuf?
And if just payload length is required one can get by subtracting (ip-hdr-len + tcp-offset) from total length in ip header ...
On Thu, Dec 6, 2018 at 11:18 AM Shyam Shrivastav <shrivastav.shyam at gmail.com> wrote:
As per my understanding
payload = (uint8_t *)tcp_hdr + (tcp_hdr->data_off << 2);
should be
payload = (uint8_t *)tcp_hdr + (tcp_hdr->data_off >> 4) << 2);
Note that data offset is 4 most significant bits of the byte, refer tcp header
On Thu, Dec 6, 2018 at 9:15 AM bai bakari <912873551 at qq.com> wrote:
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!
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