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Subject: Re: gsmtap design/extensions?
From:   Guy Harris <guy@alum.mit.edu>
In-Reply-To: <f0a64bb751b8c601f58130a7f3a3158d70f18f63.camel@sipsolutions.net>
Date:   Fri, 12 Apr 2019 12:54:47 -0700
Cc:     Harald Welte <laforge@gnumonks.org>,
        Vadim Yanitskiy <axilirator@gmail.com>,
        OpenBSC Mailing List <openbsc@lists.osmocom.org>,
        Sean Tranchetti <stranche@codeaurora.org>, radiotap@netbsd.org,
        Dan Williams <dcbw@redhat.com>, netdev@vger.kernel.org,
        linux-wireless@vger.kernel.org,
        Aleksander Morgado <aleksander@aleksander.es>,
        Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
        =?utf-8?Q?Bj=C3=B8rn_Mork?= <bjorn@mork.no>
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To:     Johannes Berg <johannes@sipsolutions.net>
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On Apr 12, 2019, at 10:15 AM, Johannes Berg <johannes@sipsolutions.net> wrote:

> Agree. Sorry about that. No disrespect was intended, but I'm still not
> sure I understand the need for UDP encapsulation *as part of the
> protocol*. I guess saying "GSMTAP can optionally be encapsulated in UDP
> with the well-known port xyz" would be something else, and it'd make
> more sense to me than saying it has to be.

I see nothing about a struct gsmtap_hdr:

	http://osmocom.org/projects/baseband/wiki/GSMTAP

that

	1) requires that it plus the payload be encapsulated in a UDP datagram

or

	2) would prevent it from being at the beginning of a LINKTYPE_GSMTAP/DLT_GSMTAP packet in a pcap or pcapng file.