All of lore.kernel.org
 help / color / mirror / Atom feed
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dimitris Michailidis <dmichail@google.com>,
	edumazet@google.com, davem@davemloft.net
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH net] net: fix pskb_trim_rcsum_slow() with odd trim offset
Date: Fri, 19 Oct 2018 17:13:59 -0700	[thread overview]
Message-ID: <a297644f-e3d5-779e-3498-e145b6fd6c3c@gmail.com> (raw)
In-Reply-To: <20181020000713.228659-1-dmichail@google.com>



On 10/19/2018 05:07 PM, Dimitris Michailidis wrote:
> We've been getting checksum errors involving small UDP packets, usually
> 59B packets with 1 extra non-zero padding byte. netdev_rx_csum_fault()
> has been complaining that HW is providing bad checksums. Turns out the
> problem is in pskb_trim_rcsum_slow(), introduced in commit 88078d98d1bb
> ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends").
> 
> The source of the problem is that when the bytes we are trimming start
> at an odd address, as in the case of the 1 padding byte above,
> skb_checksum() returns a byte-swapped value. We cannot just combine this
> with skb->csum using csum_sub(). We need to use csum_block_sub() here
> that takes into account the parity of the start address and handles the
> swapping.
> 
> Matches existing code in __skb_postpull_rcsum() and esp_remove_trailer().
> 
> Fixes: 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends")
> Signed-off-by: Dimitris Michailidis <dmichail@google.com>

Thanks a lot Dimitris for finding this.

Reviewed-by: Eric Dumazet <edumazet@google.com>

  reply	other threads:[~2018-10-20  8:22 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-20  0:07 [PATCH net] net: fix pskb_trim_rcsum_slow() with odd trim offset Dimitris Michailidis
2018-10-20  0:13 ` Eric Dumazet [this message]
2018-10-20  8:14 ` 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=a297644f-e3d5-779e-3498-e145b6fd6c3c@gmail.com \
    --to=eric.dumazet@gmail.com \
    --cc=davem@davemloft.net \
    --cc=dmichail@google.com \
    --cc=edumazet@google.com \
    --cc=netdev@vger.kernel.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.