On 1/31/2015 3:36 PM, Andrew DeMaria wrote:
> Shorewall group,
> 
> I am having a hard time connecting to a remote PPTP from a LAN computer
> and was hoping I could get some hints on what could be going wrong.
> 
> Here is what I know:
> 
> The remote VPN server is an Asus router. At time of writing it was
> 71.208.224.179.  It is setup for PPTP with 128 bit MPPE encryption.
> 
> I can connect on my android phone if I am on verizon's network, but I
> cannot connect if I am on the LAN network.  Likewise I cannot connect on
> my laptop on the LAN network.
> 
> I have run a tcpdump on the router while trying to connect to the VPN
> from the LAN.  At a high level it seems that traffic is making it
> through for the initial connection setup and there are also some further
> PPP packets but it seems that the conversation just goes silent.
> 
> I have tried setting up shorewall in two different manners with the same
> results:
> -  Using AUTOHELPERS=Yes
> -  Specifying HELPERS=amanda,ftp,irc,netbios-ns,pptp,sane,sip,snmp,tftp
> and using the following rule in conntrack:
> 
> ?if __PPTP_HELPER
> CT:helper:pptp:PO -   -   tcp 1723
> ?endif
> 
> Any ideas?
> 

Not really.

The dump shows that the required modules are loaded:

nf_conntrack_pptp      16715  3 nf_nat_pptp
nf_conntrack_proto_gre    13024  1 nf_conntrack_pptp
nf_nat                 22338  10
nf_nat_ftp,nf_nat_irc,nf_nat_sip,ipt_MASQUERADE,nf_nat_proto_gre,nf_nat_ipv4,nf_nat_pptp,nf_nat_tftp,xt_nat,iptable_nat
nf_nat_pptp            12562  0
nf_nat_proto_gre       12517  1 nf_nat_pptp
   PPTP Helper: Available

and that the helper is being applied to TCP port 1723 in the raw
PREROUTING chain:

   11   920 CT         tcp  --  *      *       0.0.0.0/0
0.0.0.0/0            tcp dpt:1723 CT helper pptp

But:

a)  LOGFILE is not properly configured in shorewall.conf, since there
are packets being logged but they are not displayed in the dump.
Remember that LOGFILE doesn't determine where messages are logged, but
rather tells Shorewall where to look for them.

b)  There are no active PPTP connections at the time the dump was taken.

-Tom
-- 
Tom Eastep        \ When I die, I want to go like my Grandfather who
Shoreline,         \ died peacefully in his sleep. Not screaming like
Washington, USA     \ all of the passengers in his car
http://shorewall.net \________________________________________________

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