[pptp-server] Anyone seen this one?

[Neale Banks]

On Mon, 15 Oct 2001, Joey Coco wrote:

> This crashes my tunnel, using Linux kernel 2.4.7,
> pppd 2.4.0b4, get this in dmesg:
> 
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> Not enough space to encrypt packet: 1494<1494+4!
> PPP: VJ decompression error

This was discussed on another list recently.  Here's what was suggested
there:

On Tue, 9 Oct 2001, Steven Ihde wrote:
> 
> Date: Tue, 9 Oct 2001 20:28:11 -0700
> From: Steven Ihde <sihde at cs.stanford.edu>
> To: Neale Banks <neale at lowendale.com.au>
> Cc: Ferenc Tamas Gyurcsan <gyurcsan at metrocast.net>, pptp at list.lameter.com
> Subject: Re: [Pptp] Not enough space in kernel....
> 
> On Wed, Oct 10, 2001 at 12:39:32PM +1000, Neale Banks wrote:
> > On Tue, 9 Oct 2001, Ferenc Tamas Gyurcsan wrote:
> > 
> > > Hi people,
> > > 
> > > I managed to get my pptp working. I'm connecting from linux to win2000.
> > > Now I get this message in syslog:
> > > 
> > > Oct  9 22:17:05 jade pppd[2159]: sent [LCP EchoReq id=0x10
> magic=0xc33c0bc5]
> > > Oct  9 22:17:05 jade pppd[2159]: rcvd [LCP EchoRep id=0x10
> magic=0x50737f9f]
> > > Oct  9 22:17:13 jade kernel: Not enough space to encrypt packet:
> 1004<1004+4!
> > > 
> > > How can I solve this problem? 
> > 
> > http://lists.schulte.org/pipermail/pptp-server/2000-July/007754.html ?
> > 
> > In your case, perhaps try mru 990 and mtu 990
> 
> I do not believe that reducing the MTU will help (the MRU is not
> relevant in this situation).  The patch available at
> 
> http://mirror.binarix.com/ppp-mppe/linux-2.4.4-openssl-0.9.6a-mppe.patch.gz
> 
> should solve this problem (it should apply relatively cleanly to any
> 2.4.x kernel version).
> 
> The problem is that ppp_generic.c assumes that no "compression" method
> will ever cause a frame to grow.  However, MPPE causes every frame to
> grow by four bytes.  This only generates the above error message when
> you are trying to send a frame that is within four bytes of the MTU.
> 
> Reducing the MTU will not help because if you reduce the MTU,
> ppp_generic.c will just reduce the size of the buffer that it passes
> to the compressor.
> 
> -Steve
> 
> 
> -- 
> Steven C. Ihde <sihde at cs.stanford.edu>
> PGP Key ID: 0x7793756D
> PGP Fingerprint:  DC 55 8B CA 50 8B DD 75  67 45 96 4D FF 42 8A 6C
> 

HTH,
Neale.