Re: the Fragment offset field in IP packet should follow the Raw bitstream？

[Jaap Keuter <jaap.keuter () xs4all nl>]

Hi,

Oh, wasn’t expecting that. Digging further in the 3.0 branch I found that the bitfield was re-introduced, in 2.4.

commit 558fe23226b69665dd66ee15bed2f7492653aa09
Author: Anders Broman <anders.broman () ericsson com>
Date:   Thu Jul 20 16:02:54 2017 +0200

    [IP] Simplify paring of flags field by using
    proto_tree_add_bitmask_with_flags().

which was changed again and subsequently fixed:

commit 89beba7ea6c4e53c53349d2dc730db6ff4644979
Author: João Valverde <joao.valverde () tecnico ulisboa pt>
Date:   Thu Jan 23 02:13:40 2020 +0000

    IPv4: Fix display of Fragment Offset field
    
Based on bug 16344 (https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=16344 
<https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=16344>)

Thanks,
Jaap


> On 21 Jun 2020, at 04:26, damker <damker () sina com> wrote:
>
> my version was 3.0.6.
> when i upgrade to 3.0.11, it shows like this "Fragment offset: 856".
>
> damker
>  
> 发件人： Jaap Keuter <mailto:jaap.keuter () xs4all nl>
> 发送时间： 2020-06-19 23:10
> 收件人： Community support list for Wireshark <mailto:wireshark-users () wireshark org>
> 主题： Re: [Wireshark-users]the Fragment offset field in IP packet should follow the Raw bitstream？
> That was a nice bit of source code archeology, but I’ve found that this format was changed in commit 7f6d5c04a86 with 
> the comment:
>
> commit 7f6d5c04a869525d31e8d6e260d5195857481031
> Author: Martin Mathieson <martin.r.mathieson () googlemail com <mailto:martin.r.mathieson () googlemail com>>
> Date:   Wed Aug 29 15:35:27 2007 +0000
>
>     Don't show fragment offset as a bit field, but note number of bits used in long text.
>     
>     svn path=/trunk/; revision=22727
>
> Note the date, that was back in 2007, so this format disappeared before Wireshark 1.0.
> Where did you get this from?
>
> Thanks,
> Jaap
>
>
> > On 19 Jun 2020, at 09:48, damker <damker () sina com <mailto:damker () sina com>> wrote:
> >
> > an IP packet decode As follows:
> >     ...
> >     Flags: 0x006b
> >         0... .... .... .... = Reserved bit: Not set
> >         .0.. .... .... .... = Don't fragment: Not set
> >         ..0. .... .... .... = More fragments: Not set
> >     ...0 0011 0101 1000 = Fragment offset: 856
> >     Time to live: 128
> >
> > I know that it says "The fragment offset is measured in units of 8 octets (64 bits)" in RFC 791.
> > my question is: Flags = 0x006b, the "...0 0011 0101 1000 = Fragment offset: 856" should be "...0 0000 0110 1011 = 
> > Fragment offset: 856"?
> > I think the second one is more clear.
> >
> >
> >
> > damker
> >  

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