DPDK patches and discussions
 help / color / mirror / Atom feed
From: Bruce Richardson <bruce.richardson@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>,
	DPDK Dev List <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] ether: mark ethernet addresses as being 2-byte aligned
Date: Mon, 1 Jul 2019 14:38:43 +0100	[thread overview]
Message-ID: <20190701133843.GC380@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <20190701131112.kdz3koexxyou466k@platinum>

On Mon, Jul 01, 2019 at 03:11:12PM +0200, Olivier Matz wrote:
> Hi Bruce,
> 
> On Thu, May 16, 2019 at 04:54:57PM +0100, Bruce Richardson wrote:
> > When including the rte_ether.h header in applications with warnings
> > enabled, a warning was given because of the assumption of 2-byte alignment
> > of ethernet addresses when processing them.
> > 
> > .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> >   struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> >   {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> >   an unaligned pointer value [-Waddress-of-packed-member]
> > 149 |  const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> >     |  ^~~~~
> > 
> > Since ethernet addresses should always be aligned on a two-byte boundary,
> 
> I'm a bit reserved about this last assumption. The ethernet address
> structure may be used in a private structure, whose alignment is 1. Are
> we sure that there is no (funny) protocol that carries unaligned
> ethernet addresses?
> 
> Shouldn't we change the definition of unaligned_uint16_t instead?
> Or change the rte_is_broadcast_ether_addr() function?
> 

We could, but I believe the correct behaviour is to make the addresses
always 2-byte aligned, unless someone actually has a real-world case where
there is a protocol that doesn't have the data 2-byte aligned.

/Bruce

  reply	other threads:[~2019-07-01 13:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16 15:54 Bruce Richardson
2019-05-16 18:04 ` Kevin Traynor
2019-05-16 20:38   ` Bruce Richardson
2019-07-01 13:11 ` Olivier Matz
2019-07-01 13:38   ` Bruce Richardson [this message]
2019-07-01 14:14     ` Olivier Matz
2019-07-01 14:28       ` Bruce Richardson
     [not found] ` <1e5856a8-108b-1f0c-6ce7-b7c9eafac658@sitilge.id.lv>
2020-02-05 13:45   ` Bruce Richardson
2020-02-09 19:32     ` Martins Eglitis

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=20190701133843.GC380@bricha3-MOBL.ger.corp.intel.com \
    --to=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=olivier.matz@6wind.com \
    --cc=stephen@networkplumber.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).