From: Stephen Hemminger <stephen@networkplumber.org>
To: "Morten Brørup" <mb@smartsharesystems.com>
Cc: <dev@dpdk.org>, "Ferruh Yigit" <ferruh.yigit@intel.com>,
"Declan Doherty" <declan.doherty@intel.com>,
"Chas Williams" <chas3@att.com>,
"John W. Linville" <linville@tuxdriver.com>,
"Marcin Wojtas" <mw@semihalf.com>,
"Michal Krawczyk" <mk@semihalf.com>,
"Guy Tzalik" <gtzalik@amazon.com>,
"Evgeny Schemeilin" <evgenys@amazon.com>,
"Ravi Kumar" <ravi1.kumar@amd.com>,
"Igor Russkikh" <igor.russkikh@aquantia.com>,
"Pavel Belous" <pavel.belous@aquantia.com>,
"Shepard Siegel" <shepard.siegel@atomicrules.com>,
"Ed Czeck" <ed.czeck@atomicrules.com>,
"John Miller" <john.miller@atomicrules.com>,
"Ajit Khaparde" <ajit.khaparde@broadcom.com>,
"Somnath Kotur" <somnath.kotur@broadcom.com>,
"Jerin Jacob" <jerin.jacob@caviumnetworks.com>,
"Maciej Czekaj" <maciej.czekaj@caviumnetworks.com>,
"Shijith Thotton" <shijith.thotton@cavium.com>,
"Srisivasubramanian Srinivasan" <ssrinivasan@cavium.com>,
"Rahul Lakkireddy" <rahul.lakkireddy@chelsio.com>,
"John Daley" <johndale@cisco.com>,
"Hyong Youb Kim" <hyonkim@cisco.com>,
"Wenzhuo Lu" <wenzhuo.lu@intel.com>,
"Konstantin Ananyev" <konstantin.ananyev@intel.com>,
"Beilei Xing" <beilei.xing@intel.com>,
"Qi Zhang" <qi.z.zhang@intel.com>,
"Xiao Wang" <xiao.w.wang@intel.com>,
"Jingjing Wu" <jingjing.wu@intel.com>,
"Tomasz Duszynski" <tdu@semihalf.com>,
"Dmitri Epshtein" <dima@marvell.com>,
"Natalie Samsonov" <nsamsono@marvell.com>,
"Zyta Szpak" <zr@semihalf.com>,
"Matan Azrad" <matan@mellanox.com>,
"Shahaf Shuler" <shahafs@mellanox.com>,
"Yongseok Koh" <yskoh@mellanox.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
"Haiyang Zhang" <haiyangz@microsoft.com>,
"Jan Remes" <remes@netcope.com>,
"Alejandro Lucero" <alejandro.lucero@netronome.com>,
"Hemant Agrawal" <hemant.agrawal@nxp.com>,
"Shreyansh Jain" <shreyansh.jain@nxp.com>,
"Gagandeep Singh" <g.singh@nxp.com>,
"Pankaj Chauhan" <pankaj.chauhan@nxp.com>,
"Harish Patil" <harish.patil@cavium.com>,
"Rasesh Mody" <rasesh.mody@cavium.com>,
"Shahed Shaikh" <shahed.shaikh@cavium.com>,
"Andrew Rybchenko" <arybchenko@solarflare.com>,
"Yong Wang" <yongwang@vmware.com>,
"Maxime Coquelin" <maxime.coquelin@redhat.com>,
"Tiwei Bie" <tiwei.bie@intel.com>,
"Zhihong Wang" <zhihong.wang@intel.com>,
"Allain Legacy" <allain.legacy@windriver.com>,
"Matt Peters" <matt.peters@windriver.com>,
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"Tetsuya Mukawa" <mtetsuyah@gmail.com>,
"Gaetan Rivet" <gaetan.rivet@6wind.com>,
"Jasvinder Singh" <jasvinder.singh@intel.com>,
"Cristian Dumitrescu" <cristian.dumitrescu@intel.com>
Subject: Re: [dpdk-dev] [RFC] Ethernet drivers to add padding on egress
Date: Mon, 19 Nov 2018 08:10:27 -0800 [thread overview]
Message-ID: <20181119081010.44e7bbd9@xeon-e3> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35B424A6@smartserver.smartshare.dk>
On Thu, 15 Nov 2018 17:56:48 +0100
Morten Brørup <mb@smartsharesystems.com> wrote:
> Hi networking driver maintainers,
>
> I suggest that the TX functions of Ethernet interface drivers accept packets with less than 60 byte payload, and transmit them on the medium as valid Ethernet frames, i.e. by padding the packets up to the minimum Ethernet packet size of 64 bytes incl. Ethernet FCS, instead of discarding them.
>
> This feature makes it easier for application developers who are using DPDK as the lower layer in an IP stack, where lots of packets have less than 60 bytes Ethernet payload, e.g. TCP SYN and TCP ACK packets.
>
> This feature also makes it easier for application developers who are using DPDK library functions that split, merge or otherwise transform packets into packets of other sizes, e.g. Generic Segmentation Offload, IP Fragmentation and various tunnel encapsulation/decapsulation functions.
>
> Currently (without this feature), it is required by the application to check if packets originating from the IP stack or having passed through a split/merge/transform function are about to egress on an Ethernet interface, and in that case, if some of the packets are less than 60 bytes (excl. Ethernet FCS), add padding before passing them on to the driver's TX function.
>
> E.g. when using Generic Segmentation Offload, a packet carrying 1461 byte TCP payload (excl. 54 bytes Ethernet+IP+TCP headers) will be split into two packets of respectively 1514 byte (incl. 54 bytes Ethernet+IP+TCP headers) and 55 bytes (incl. 54 bytes Ethernet+IP+TCP headers), and the latter must be padded before it is transmitted on an Ethernet interface.
>
>
> In my opinion, it should be a requirement that the Ethernet interface drivers ensure correct padding when egressing the packet on the medium. Alternatively, it can be an optional feature, which could be exposed as an TX Capabilities flag of the driver.
>
> What do you think?
>
>
> I do not suggest any changes regarding ingress - runts (undersize Ethernet packets) received from the medium are invalid, and should be discarded and counted as errors.
>
Devices drivers should work like Linux and BSD!
They must pad packets to meet any restrictions by the underlying technology.
Please don't add another capability flag or other way for applications to see this.
DPDK already has way to many hardware capability flags.
It should just happen.
next prev parent reply other threads:[~2018-11-19 16:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-15 16:56 Morten Brørup
2018-11-19 8:02 ` Shahaf Shuler
2018-11-21 0:55 ` Stephen Hemminger
2018-11-19 16:10 ` Stephen Hemminger [this message]
2018-11-20 8:16 ` Shahaf Shuler
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