Re: PPTP passthrough

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On 04/05/17 08:07, Rob Sterenborg (Lists) wrote:
On 04/05/17 05:42, Steven O'Connor wrote:
On 04/05/17 00:45, Rob Sterenborg (lists) wrote:
On 3-5-2017 04:13, Steven O'Connor wrote:
PPTP pass-through seems to be broken. When the client tries to connect, a gre packet is sent but the reply gre packet is dropped at my firewall.

The relevant conntrack dump shows a mismatch between the expected reply and the packet received, srckey/dstkey do not match. Is that significant?


gre      47 27 src=aaa.bbb.cc.ddd dst=www.xxx.yy.zz srckey=0x0
dstkey=0xb053 [UNREPLIED] src=www.xxx.yy.zz dst=aaa.bbb.cc.ddd
srckey=0xb053 dstkey=0x0 mark=0 use=1
gre      47 27 src=192.168.0.212 dst=aaa.bbb.cc.ddd srckey=0x0
dstkey=0x1380 [UNREPLIED] src=aaa.bbb.cc.ddd dst=www.xxx.yy.zz
srckey=0x1380 dstkey=0x0 mark=0 use=1

You don't show any rules, so just a guess.
Do you allow/forward protocol 47 (gre) packets?


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Rob

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The default policy LAN->NET is accept. I have also added a rule to accept gre.

It has been working previously but after an update to the kernel or shorewall it has stopped working. I only use pptp occasionally so I cannot be sure when it stopped.

The firewall can accept pptp connections from the net and it is only the passthru that is broken.

IIRC something changed with autoloading helper modules (don't know exactly when): are the PPTP helper modules loaded?

nf_nat_pptp.ko
nf_conntrack_pptp.ko

You would need nf_nat_pptp.ko for NAT-ing the PPTP protocol.

Oh, and lets not forget:

nf_nat_proto_gre.ko
nf_conntrack_proto_gre.ko


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Rob
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