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Old 08-19-2016, 06:02 PM   #1
vbsaltydog
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PPTP issue


Home: Linksys router running dd-wrt firmware as a VPN server.

Remote: 2 x Raspberry Pi running the OSMC OS (Debian Jessie based)

Background: raspi2's OS is a dd copy of raspi1 so the two raspi's are configured identically, with unique ip addresses, of course.

The raspi's use the pptp-linux package for the vpn client.

Raspi1 can connect to my home VPN server without issue.

Raspi2 runs sudo pon tunnel-name and the VPN server shows the tunnel in the output of ps but there is no interface such as ppp1 (since ppp0 already exists). The raspi2 ifconfig shows no pptp interface.

Any idea why the same VPN config on two different devices that use a mirrored OS have different results when trying to establish a VPN connection?

Thanks
 
Old 08-20-2016, 12:40 PM   #2
scheidel21
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Have you looked at the log files for the client and server? If so have you enabled a higher level of logging to get more detailed information? I would start there to see if there are any clues as to why it's failing. If you want to post the logs we can help you interpret them to resolve the issue if you like.
 
Old 08-20-2016, 01:35 PM   #3
vbsaltydog
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Yes, I have run the pon command with the debug flags and there is nothing in the output except for the reading of the config values from the pptp.options and /etc/ppp/peers/my_tunnel files. The last line of output says using channel 1171 (this number changes across multiple executions of pon).

The options are the same on the raspi that connects and the raspi that does not connect so I doubt its a config setting. As stated, the vpn server gets the request and builds the tunnel (temporarily) but neither the client or the server build the pptp interfaces and the tunnel process goes away after a few seconds.

I dont know if dd-wrt logs the connection details anywhere, since it runs mostly from an nvram environment, but I will look to see if the tunnel process logs anything server side.
 
Old 08-20-2016, 05:09 PM   #4
vbsaltydog
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Here are the vpn server logs:

Successful raspi client connection:

Aug 20 21:22:48 DD-WRT daemon.info pptpd[18597]: CTRL: Client 73.216.228.239 control connection started
Aug 20 21:22:49 DD-WRT daemon.info pptpd[18597]: CTRL: Starting call (launching pppd, opening GRE)
Aug 20 21:22:49 DD-WRT daemon.notice pppd[18598]: pppd 2.4.4 started by root, uid 0

Unsuccessful raspi client connection:

Aug 20 22:40:19 DD-WRT daemon.info pptpd[19582]: CTRL: Client 73.216.228.239 control connection started
Aug 20 22:40:20 DD-WRT daemon.info pptpd[19582]: CTRL: Starting call (launching pppd, opening GRE)
Aug 20 22:40:20 DD-WRT daemon.notice pppd[19584]: pppd 2.4.4 started by root, uid 0
Aug 20 22:40:50 DD-WRT daemon.info pppd[19584]: Exit.
Aug 20 22:40:50 DD-WRT daemon.err pptpd[19582]: GRE: read(fd=9,buffer=420c6c,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs
Aug 20 22:40:50 DD-WRT daemon.err pptpd[19582]: CTRL: PTY read or GRE write failed (pty,gre)=(9,10)
Aug 20 22:40:50 DD-WRT daemon.debug pptpd[19582]: CTRL: Reaping child PPP[19584]
Aug 20 22:40:50 DD-WRT daemon.info pptpd[19582]: CTRL: Client 73.216.228.239 control connection finished


Any help is appreciated.
 
Old 08-20-2016, 06:05 PM   #5
scheidel21
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What does the pppd log say it's terminating due to a GRE packet error, even says to check the log. Config files for clients and server pptp would be useful too.
 
Old 08-20-2016, 06:18 PM   #6
vbsaltydog
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I dont know where the pptp log is located. This is a dd-wrt firmware router vs a full linux distro so the logging is very lean and in non-standard locations.

I will poke around and see if I can locate one, assuming one even exists.
 
Old 08-20-2016, 06:23 PM   #7
scheidel21
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Try /var/log/messages
 
Old 08-20-2016, 06:26 PM   #8
vbsaltydog
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Thats where the logs came from that I shared.
 
Old 08-20-2016, 06:56 PM   #9
scheidel21
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Ok then, guess we're SOL on the pppd log then, from what i read about logging in dd-wrt.
 
Old 08-20-2016, 06:59 PM   #10
vbsaltydog
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It looks like the most valuable clues are:

Aug 20 22:40:50 DD-WRT daemon.err pptpd[19582]: CTRL: PTY read or GRE write failed (pty,gre)=(9,10)
Aug 20 22:40:50 DD-WRT daemon.debug pptpd[19582]: CTRL: Reaping child PPP[19584]
 
Old 08-20-2016, 07:04 PM   #11
scheidel21
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Yes it is, but I would like to see the config for both clients and the dd-wrt pptp server.
 
Old 08-20-2016, 07:06 PM   #12
scheidel21
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Take a look at this, similar language in his logs.
 
Old 08-20-2016, 07:06 PM   #13
scheidel21
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Helps if I paste it http://serverfault.com/questions/276...tp-vpn-problem
 
Old 08-20-2016, 07:24 PM   #14
vbsaltydog
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Client config for both raspi devices:

/etc/ppp/options.pptp

lock
noauth
refuse-pap
refuse-eap
refuse-chap
refuse-mschap
nobsdcomp
nodeflate

/etc/ppp/peers/tunnel_name

remotename tunnel_name
linkname tunnel_name
ipparam tunnel_name
pty "pptp 6QWLakYAguf45UMK.mooo.com --nolaunchpppd "
name user_name (different on each raspi device)
usepeerdns
require-mppe
refuse-eap
noauth

# adopt defaults from the pptp-linux package
file /etc/ppp/options.pptp

/etc/ppp/chap-secrets

user_name tunnel_name password * (user_name is different on each raspi device)

Last edited by vbsaltydog; 08-20-2016 at 07:25 PM.
 
Old 08-20-2016, 07:30 PM   #15
vbsaltydog
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VPN Server options.pptpd
lock
name *
proxyarp
ipcp-accept-local
ipcp-accept-remote
lcp-echo-failure 10
lcp-echo-interval 5
deflate 0
auth
-chap
-mschap
+mschap-v2
mppe required,stateless
mppc
ms-ignore-domain
chap-secrets /tmp/pptpd/chap-secrets
ip-up-script /tmp/pptpd/ip-up
ip-down-script /tmp/pptpd/ip-down
mtu 1450
mru 1450
ms-dns 10.10.24.240
 
  


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