Re: [Ethereal-dev] displaying OSI packets inside GRE tunnels

[Hannes Gredler <hannes@xxxxxxxxxxx>]

On Thu, Nov 07, 2002 at 02:13:05PM -0800, Guy Harris wrote:
| On Thu, Nov 07, 2002 at 11:01:43AM +0100, Hannes Gredler wrote:
| > pls find a patch that shows now OSI in GRE tunneled packets
| > that the payload is OSI and not "unknown";
| 
| Checked in (although I got the OSI SAP value from "llcsaps.h" rather
| than adding it to "greproto.h").

thats one of the odd things in GRE - the protocol ID of the payload
is actually an ethertype - however for OSI - never ethertypes have been used;
in the OSI world always LLC  was used to frame packets;

so what needs to be done is actually an ugly beast: an ethertype
value based on the OSI DSAP; and thats the reason why
i decided not to use the plain OSI SAP value but rather
composing the ethertype and putting it in greproto.h;
in GRE we do have the only occurence of that custom ethertype;

BTW cisco HDLC used a similar ethertyped version - here the value is
0xFEFE;

so conclusion is: semantically it would belong to ethertype.h ;-)

/hannes