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From: Padam Jeet Singh <padam.singh@inventum.net>
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Date: Wed, 28 Oct 2015 12:20:22 +0530
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Subject: [dpdk-dev] Wrong TCP Checkum computed by hardware
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Hi,

While implementing a sample packet generation code, I am setting up the =
offload flags so that the hardware (82599ES in my case) computes the IP =
and TCP Checksums. However, it seems that only the IP checksum is =
computed whereas the TCP Checksum is computed, but computed wrong. Here =
is a snippet of what I doing:

/* First reset all offload flags */
mbuf->ol_flags =3D (uint16_t) (mbuf->ol_flags & (~PKT_TX_OFFLOAD_MASK));
/* Then enable IP Checksum offload */
mbuf->ol_flags |=3D PKT_TX_IP_CKSUM;
/* This is required to be set to 0 */
ipv4hdr->hdr_checksum =3D 0;
mbuf->ol_flags |=3D PKT_TX_TCP_CKSUM;
/* Compute the PSD header */
tcphdr->cksum =3D rte_ipv4_phdr_cksum(ipv4hdr);

When I replace the checksum computation from hardware-offload to a =
software implementation, the checksum computed is correct. I have =
verified both the cases with Wireshark on the system receiving the =
packets.

Any hint what could I be doing wrong here?

Thanks,
Padam=