All of lore.kernel.org
 help / color / mirror / Atom feed
From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Alexander Duyck <alexander.duyck@gmail.com>,
	Sowmini Varadhan <sowmini.varadhan@oracle.com>
Cc: Tom Herbert <tom@herbertland.com>,
	David Miller <davem@davemloft.net>,
	Netdev <netdev@vger.kernel.org>, Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH net] net: Allow flow dissector to handle non 4-byte aligned headers
Date: Tue, 2 Feb 2016 14:41:23 +0100	[thread overview]
Message-ID: <56B0B203.3060700@stressinduktion.org> (raw)
In-Reply-To: <CAKgT0UfjLEBUeiV3WS2BC=yRkxi9JBF4mqJ=niXOUQnhkiMhvA@mail.gmail.com>

On 02.02.2016 04:56, Alexander Duyck wrote:
>> @@ -394,7 +407,7 @@ ip_proto_again:
>>                                                     data, hlen, &_eth);
>>                          if (!eth)
>>                                  goto out_bad;
>> -                       proto = eth->h_proto;
>> +                       proto = get_unaligned_be16(&eth->h_proto);
>>                          nhoff += sizeof(*eth);
>>                  }
>
> This piece doesn't make any sense to me.  It is already only 2 bytes
> wide.  I'm not sure why we should be seeing this trigger an unaligned
> access.  Are you sure it wasn't something like the keyid causing the
> issue?  I'd be interested in seeing what the compiler did here that it
> is triggering the problem.
>

Correct, and the __packed attribute of struct ethhdr already causes all 
members to have an assumed-alignment of '1', so gcc doesn't create any 
16 bit width accesses anyway.

Bye,
Hannes

  reply	other threads:[~2016-02-02 13:41 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-31 21:37 [PATCH net] net: Allow flow dissector to handle non 4-byte aligned headers Tom Herbert
2016-01-31 21:47 ` kbuild test robot
2016-01-31 22:06 ` Florian Westphal
2016-02-01  0:24 ` Eric Dumazet
2016-02-01  0:39   ` Florian Fainelli
2016-02-01 15:20     ` Nicolas Dichtel
2016-02-01 16:01       ` Sowmini Varadhan
2016-02-01  0:43   ` Sowmini Varadhan
2016-02-01 12:32 ` Sergei Shtylyov
2016-02-02  0:31 ` Sowmini Varadhan
2016-02-02  0:46   ` Tom Herbert
2016-02-02  3:56   ` Alexander Duyck
2016-02-02 13:41     ` Hannes Frederic Sowa [this message]
2016-02-02 18:35     ` Sowmini Varadhan
2016-02-03 17:07   ` Tom Herbert
2016-02-03 17:31     ` Sowmini Varadhan
2016-02-03 17:51       ` Tom Herbert
2016-02-03 17:59         ` Sowmini Varadhan

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=56B0B203.3060700@stressinduktion.org \
    --to=hannes@stressinduktion.org \
    --cc=alexander.duyck@gmail.com \
    --cc=davem@davemloft.net \
    --cc=kernel-team@fb.com \
    --cc=netdev@vger.kernel.org \
    --cc=sowmini.varadhan@oracle.com \
    --cc=tom@herbertland.com \
    /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.