Messages in this thread | | | Date | Wed, 21 May 2003 18:09:17 +1000 | From | Menno Smits <> | Subject | Re: Kernel panic with pptpd when mss > mtu |
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Thanks for the quick and useful reply.
On Tue, 20 May 2003 21:43:01 -0700 Frank Cusack <fcusack@fcusack.com> wrote:
> On Wed, May 21, 2003 at 09:14:42AM +1000, Menno Smits wrote: > > I'm seeing a kernel oops with 2.4.20 which seems to be related to the > > PopTop PPTP server. When certain clients connect in (seems to be > > Win98) and begin large data transfers the kernel will reliably oops. > > The system crashes hard, the oops doesn't make it to the logs. > ... > > I have been able to deal with the issue by using the workaround > > suggested in the the second post. That is, adding netfilter rules with > > the TCPMSS target to limit the TCP MSS to PMTU - 40. Apparently the > > problem is triggered by the MSS being bigger than the MTU (which is > > 750 in this case). > > Yup. win98 ignores the negotiated MRU from the PPP peer (MTU on the win98 > side) and sends PPP packets larger than MTU. As you've discovered. :-) > > Linux doesn't allocate enough space for the decompressor output, and the > mppe module doesn't properly check that enough space exists. (That's > because PPP MPPE packets *shrink* after "decompression", and the mppe > module assumes at least the same amount of space as the PPP packet is > allocated for the decompressor.)
That certainly makes sense.
> Grab the latest ftp://ftp.samba.org/pub/unpacked/ppp which corrects both > of the above problems.
I'll try this and let you know how I go.
> I'll be posting a patch to lkml to correct the decompressor allocation > problem, shortly (a few weeks).
Look forward to it.
Regards, Menno Smits - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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