[pptp-server] Impossible GRE packet

[Fu Ming]

Hi,

I come across a GRE packet sent by an NT4 box, see my tcpdump:

17:02:29.829533 gre-proto-0x880B (gre encap)

4500 002c 01f0 0000 802f 5995 c0a8 0016

c81c 5643 3081 880b 0008 0000 0000 0049

0000 0025 ff03 c021 060f 0004 0800

the IP length is two byte shorter than what is sent over the wire. What should I do to this kind of packet when passing it through a firewall. I have tried to increase the IP length by two byte, or chop off the extra two byte, none of them seams to be what the NT4 box willing to accept.

Any suggestion is very much appreciated,

============================   
   Ming Fu
   Borderware Technologies, Inc.
   http://www.borderware.com
   fming at borderware.com
   (905)804-1855 Ext 229
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