From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Ben Dooks <ben.dooks@codethink.co.uk>, netdev@vger.kernel.org
Cc: oneukum@suse.com, davem@davemloft.net, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org, steve.glendinning@shawell.net,
linux-kernel@lists.codethink.co.uk
Subject: Re: [PATCH 4/4] usbnet: smsc95xx: check for csum being in last four bytes
Date: Wed, 14 Nov 2018 18:59:02 +0300 [thread overview]
Message-ID: <8b5a1bc6-c762-0e50-c602-fe4a9876d246@cogentembedded.com> (raw)
In-Reply-To: <20181114115022.9584-5-ben.dooks@codethink.co.uk>
On 11/14/2018 02:50 PM, Ben Dooks wrote:
> The manual states that the checksum cannot lie in the last DWORD of the
> transmission, so add a basic check for this and fall back to software
> checksumming the packet.
>
> This only seems to trigger for ACK packets with no options or data to
> return to the other end, and the use of the tx-alignment option makes
> it more likely to happen.
>
> Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
> ---
> Fixes for v2:
> - Fix spelling of check at Sergei's suggestion
> - Move skb->len check into smsc95xx_can_tx_checksum()
> - Change name of smsc95xx_can_checksum to explicitly say it is tx-csum
> ---
> drivers/net/usb/smsc95xx.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
> index 8f7c473f3260..cc78ef78cc93 100644
> --- a/drivers/net/usb/smsc95xx.c
> +++ b/drivers/net/usb/smsc95xx.c
> @@ -1997,6 +1997,23 @@ static u32 smsc95xx_calc_csum_preamble(struct sk_buff *skb)
> return (high_16 << 16) | low_16;
> }
>
> +/* The TX CSUM won't work if the checksum lies in the last 4 bytes of the
> + * transmission. This is fairly unlikely, only seems to trigger with some
> + * short TCP ACK packets sent.
> + *
> + * Note, this calculation should probably check for the alignment of the
> + * data as well, but a straight check for csum being in the last four bytes
> + * of the packet should be ok for now.
> +*/
Missed a space before */.
[...]
MBR, Sergei
next prev parent reply other threads:[~2018-11-14 15:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 11:50 SMSC95xx driver updates (round 1) Ben Dooks
2018-11-14 11:50 ` [PATCH 1/4] usbnet: smsc95xx: fix rx packet alignment Ben Dooks
2018-11-14 11:50 ` [PATCH 2/4] usbnet: smsc95xx: simplify tx_fixup code Ben Dooks
2018-11-14 11:50 ` [PATCH 3/4] usbnet: smsc95xx: fix memcpy for accessing rx-data Ben Dooks
2018-11-14 11:50 ` [PATCH 4/4] usbnet: smsc95xx: check for csum being in last four bytes Ben Dooks
2018-11-14 15:59 ` Sergei Shtylyov [this message]
2018-11-14 11:58 ` SMSC95xx driver updates (round 1) Oliver Neukum
2018-11-15 18:06 ` Woojung.Huh
2018-11-16 10:49 ` Ben Dooks
2018-11-17 4:16 ` David Miller
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=8b5a1bc6-c762-0e50-c602-fe4a9876d246@cogentembedded.com \
--to=sergei.shtylyov@cogentembedded.com \
--cc=ben.dooks@codethink.co.uk \
--cc=davem@davemloft.net \
--cc=linux-kernel@lists.codethink.co.uk \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=oneukum@suse.com \
--cc=steve.glendinning@shawell.net \
/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).