DPDK usage discussions
 help / color / mirror / Atom feed
From: Stephen Hemminger <stephen@networkplumber.org>
To: "jiangheng (H)" <jiangheng12@huawei.com>
Cc: "users@dpdk.org" <users@dpdk.org>
Subject: Re: [dpdk-users] DPDK RX TCP checksum failed
Date: Sat, 26 Mar 2022 11:59:23 -0700
Message-ID: <20220326115923.715473aa@hermes.local> (raw)
In-Reply-To: <cb53d6174669407b96a0f6a09d6bf134@huawei.com>

On Sat, 26 Mar 2022 08:13:21 +0000
"jiangheng (H)" <jiangheng12@huawei.com> wrote:

> Hi all,
> I tried using the checksum offloads feature in DPDK and it did not see working under virtual machine.
> Port only support TCP checksum and do not support IP checksum:
> rx_offload_capa = DEV_RX_OFFLOAD_TCP_CKSUM
> tx_offload_capa = DEV_TX_OFFLOAD_TCP_CKSUM
> so I config rxmode.offload txmode.offloads as below:
> rxmode.offloads = DEV_RX_OFFLOAD_TCP_CKSUM
> txmode.offloads = DEV_TX_OFFLOAD_TCP_CKSUM
> For TX, I set the following parameters, it works good.
> mbuf->l2_len = sizeof(*ethhdr)
> mbuf->l3_len = ip header len
> mbuf-ol_flags = RTE_MBUF_F_TX_IPV4 | RTE_MBUF_F_TX_TCP_CKSUM

Virtio does not support IP checksum offload.  Because Virtio passes
packets to Linux kernel, and Linux kernel does not do IP checksum offload.
The IP checksum is so trivial it is faster for most things to just
do it in software; the header is only 20 bytes and it will be in cache.

You should always check device capability before enabling an offload.

> For RX, It will execute the following code:
> In drivers/net/virtio/virtio_rxtx.c  virtio_rx_offload function :
>     if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
>         hdrlen = hdr_lens.l2_len + hdr_lens.l3_len + hdr_lens.l4_len;
>         if (hdr->csum_start <= hdrlen && l4_supported) {
>             m->ol_flags |= RTE_MBUF_F_RX_L4_CKSUM_NONE;
>         } else {
> m->ol_flags set to RTE_MBUF_F_RX_L4_CKSUM_NONE, causing the TCP RX checksum failed.
> How do I avoid the above code going into this branch?

If you want TCP checksum offload you have to set RTE_ETH_RX_OFFLOAD_TCP_CKSUM
in the rxmode when port is configured.  This will tell virtio to ask the
host to do rx offload. Again, virtio does not do IP checksum offload and
you should always query device capability first.

  reply	other threads:[~2022-03-26 18:59 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-26  8:13 jiangheng (H)
2022-03-26 18:59 ` Stephen Hemminger [this message]
2022-03-28  1:50   ` 答复: " jiangheng (H)
2022-03-28  2:15     ` Harold Huang
2022-04-07 12:50       ` 答复: " jiangheng (H)
2022-03-28  3:11   ` fwefew 4t4tg
2022-04-07 13:42     ` 答复: " jiangheng (H)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220326115923.715473aa@hermes.local \
    --to=stephen@networkplumber.org \
    --cc=jiangheng12@huawei.com \
    --cc=users@dpdk.org \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK usage discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror http://inbox.dpdk.org/users/0 users/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 users users/ http://inbox.dpdk.org/users \
	public-inbox-index users

Example config snippet for mirrors.
Newsgroup available over NNTP:

AGPL code for this site: git clone https://public-inbox.org/public-inbox.git