Your filter was "show me all packets containing the UDP protocol".
Did the filter the ICMP packet contain a header for the UDP protocol or not?
On Mon, 21 Mar 2005 20:25:22 -0800, Bob Snyder <bob.snyder@xxxxxxx> wrote:
> I disagree with the notion that when filtering for UDP, if it didn't
> display ICMP packets that come back, Ethereal would be broken. The
> headers inside the ICMP message are effectively it's payload - it's
> still an ICMP packet, not UDP (or whatever). The frame does not contain
> UDP datagrams (or whatever other protocol caused the ICMP message). And
> it's presumptuous of the program (dare I say the devs?) to presume that
> you must surely want to see the ICMP messages when what your display
> filter asks for is only the original message packets.
>
> The argument that you can use "udp and not icmp" to only see the
> original UDP seems backwards to me. You should be able to use "udp" to
> see only the UDP, and "udp and icmp" when you want to see both. Surely
> that is more intuitive.
>
> That said, I think using the UDP (or whatever) dissector to decode the
> header data included in the ICMP messages is brilliant :-)
>
> Bob S.
>
>
> ronnie sahlberg wrote:
>
> >That is what is supposed to happen.
> >
> >Rationale:
> >You asked for all packets containing the UDP protocol and you got them.
> >
> >An analyzer that filtered for UDP and did not show you these pacekts
> >to you would be broken. Ethereal is not broken in this regard.
> >
> >
> >
> >
> >On Sun, 20 Mar 2005 12:14:27 -0800, Bob Snyder <bob.snyder@xxxxxxx> wrote:
> >
> >
> >>Why are ICMP packets displayed when a display filter is used that should
> >>exclude them?
> >>
> >>For example, when running a traceroute, and with a display filter of
> >>"udp", in addition to the outbound UDP datagrams, the ICMP messages
> >>returned from each router are displayed as well. I know that the ICMP
> >>datagrams include the headers of the datagrams that are being reported
> >>on, but apparently their presence allows them to pass through the
> >>display filter. Is this behavior intentional? If so, what is the
> rationale?
> >>
> >>Bob Snyder
> >>
> >>
>
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