[pptp-server] IPTables and GRE

[Eirik Robertstad]

Looks like I did have it correct then.  I've added this for the input 
rules and the output rules... yet I'm still getting the same errors.  I 
thought it was the firewall blocking it, but I've even tryed to open the 
firewall totaly open.  I've also looked in tcpdump for any data on the 
GRE protocal, but nothing shows up.  Only activity on the port 1723. 
Windows just reports:

Error 629: You have been disconnected from the computer you dialed. 
Double-click the connection to try again.

And pptpd just shows:

<snip>
Apr 17 23:02:25 transfire pptpd[23878]: MGR: Reaped child 24169
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: local address = 172.18.0.2
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: remote address = 172.18.0.52
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Client 198.138.97.250 
control connection started
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Received PPTP Control 
Message (type: 1)
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Made a START CTRL CONN 
RPLY packet
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: I wrote 156 bytes to the 
client.
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Sent packet to client
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Received PPTP Control 
Message (type: 7)
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Set parameters to 0 
maxbps, 16 window size
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Made a OUT CALL RPLY packet
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Starting call (launching 
pppd, opening GRE)
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: pty_fd = 4
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: tty_fd = 5
Apr 17 23:02:25 transfire pptpd[24170]: CTRL (PPPD Launcher): Connection 
speed = 115200
Apr 17 23:02:25 transfire pptpd[24170]: CTRL (PPPD Launcher): local 
address = 172.18.0.2
Apr 17 23:02:25 transfire pptpd[24170]: CTRL (PPPD Launcher): remote 
address = 172.18.0.52
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: I wrote 32 bytes to the 
client.
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Sent packet to client
Apr 17 23:02:25 transfire pptpd[24169]: GRE: 
read(fd=4,buffer=809c180,len=8196) from PTY failed: status = -1 error = 
Input/output error
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: PTY read or GRE write 
failed (pty,gre)=(4,5)
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Client 198.138.97.250 
control connection finished
Apr 17 23:02:25 transfire pptpd[24169]: CTRL: Exiting now

</snip>

I'm at a total loss, I can't get any more information out of pptpd of 
what would be going on.

Thanks,
Eirik Robertstad

Matthew Drobnak wrote:

> 
> Afaik, the only two rules you'll need are to allow incoming traffic using
> protocol
> number 47, as well as TCP port 1723. If you're restricting outbound
> traffic, add
> outgoing rules as well.
> 
> 
> iptables -A INPUT -j ACCEPT -i ethX --proto 47
> iptables -A INPUT -j ACCEPT -i ethX -p tcp --dport 1723
> 
> 
> Hope that helps. The -i ethX is optional -- it allows traffic only on that
> interface.
> 
> -Matthew Drobnak
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