netdev - Re: [PATCH net-next 3/4] 6lowpan: the two bytes of u16 tag needs to be stored/accessed the other way around

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Date:	Tue, 12 Jun 2012 22:07:12 +0400
From:	Alexander Smirnov <alex.bluesman.smirnov@...il.com>
To:	Tony Cheneau <tony.cheneauh@...esiak.org>
Cc:	netdev@...r.kernel.org, linux-zigbee-devel@...ts.sourceforge.net
Subject: Re: [PATCH net-next 3/4] 6lowpan: the two bytes of u16 tag needs to
 be stored/accessed the other way around

2012/6/11 Tony Cheneau <tony.cheneauh@...esiak.org>:
> Or else, tag values, as displayed with a trafic analyser, such a
> Wireshark, are not properly displayed (e.g. 0x01 00 insted of 0x00 01,
> and so on). ---
>  net/ieee802154/6lowpan.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
> index af4f29b..af2f12e 100644
> --- a/net/ieee802154/6lowpan.c
> +++ b/net/ieee802154/6lowpan.c
> @@ -307,7 +307,7 @@ static u16 lowpan_fetch_skb_u16(struct sk_buff *skb)
>
>        BUG_ON(!pskb_may_pull(skb, 2));
>
> -       ret = skb->data[0] | (skb->data[1] << 8);
> +       ret = (skb->data[0] << 8) | skb->data[1];

This function aimed to obtain u16 from skb, why did you change the
byte-order here instead of 'tag' variable byte-shifting? Will this
code work properly on the both little and big-endian machines? Please
rework this to keep order properly for all the architectures.

>        skb_pull(skb, 2);
>        return ret;
>  }
> @@ -1002,8 +1002,8 @@ lowpan_skb_fragmentation(struct sk_buff *skb)
>        /* first fragment header */
>        head[0] = LOWPAN_DISPATCH_FRAG1 | (payload_length & 0x7);
>        head[1] = (payload_length >> 3) & 0xff;
> -       head[2] = tag & 0xff;
> -       head[3] = tag >> 8;
> +       head[2] = tag >> 8;
> +       head[3] = tag & 0xff;
>
>        err = lowpan_fragment_xmit(skb, head, header_length, 0, 0);
>
> --
> 1.7.3.4
>
>
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