DPDK usage discussions
 help / color / mirror / Atom feed
From: "Nicolson Ken (ニコルソン ケン)" <ken.nicolson@jp.panasonic.com>
To: "users@dpdk.org" <users@dpdk.org>
Subject: mbuf data is 1400 bytes but the most common (?) use, Ethernet II frames, allow for 1518 bytes
Date: Wed, 4 Oct 2023 06:52:39 +0000	[thread overview]
Message-ID: <TYAPR01MB63783D1668F3140BB5D2674DBCCBA@TYAPR01MB6378.jpnprd01.prod.outlook.com> (raw)

Hi all,

Looking at sending Ethernet packets over a DPDK connection, I see that an Ethernet Type II frame has 1518 max, but mbuf's data block is 1400 bytes.

Is this what the headroom and tailroom are for? I see example code that uses the headroom for the MAC Header, but what is the preferred way of copying a 1518 Ethernet packet into an mbuf? Should I use rte_pktmbuf_append() to reserve the extra bytes, or is there a better way?

Thanks,
Ken


             reply	other threads:[~2023-10-04  6:52 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-04  6:52 Nicolson Ken (ニコルソン ケン) [this message]
2023-10-04  7:19 ` Dmitry Kozlyuk
2023-10-05  2:28   ` Nicolson Ken (ニコルソン ケン)

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:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

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

  git send-email \
    --in-reply-to=TYAPR01MB63783D1668F3140BB5D2674DBCCBA@TYAPR01MB6378.jpnprd01.prod.outlook.com \
    --to=ken.nicolson@jp.panasonic.com \
    --cc=users@dpdk.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).