[Openswan Users] xl2tpd seems to cause packets to get mangled or disappear

[Ray Overland]

I have successfully set up an Openswan 2.9 server with xl2tpd 1.1.11 and pppd 2.4.4 on an 
IXP425 embedded networking device. Thanks Jacco! But it is still not as stable as I need 
it to be. I started doing some throughput testing using the following setup:

Windows<----------------->OpenSwan<------------------Linux
FTP Client					FTP Server
200.1.1.1           200.1.1.3  192.168.3.2		192.168.3.3
ppp-192.168.3.192

I noticed that the syslog was filling with the message:
"pppd[917]: Protocol-Reject for unsupported protocol 0xb6f1"
where the protocol number is random.

By sniffing packets with Wireshark, I determined that packets were getting mangled or 
disappearing between the ppp0 interface and the ipsec0 interface.

I enabled debugging in xl2tpd and saw the debug message:
"Oops, lost a packet or two...."
occurring many, many times in the syslog.

Looking closer at the sniffer logs, I found that some packets were being mangled by xl2tpd 
   causing windows to think that the packet was an LCP packet requesting an unknown 
protocol, and subsequently windows sent back an LCP Protocol reject message to the ppp0 
interface on the Openswan server. The other manifestation was that packets were simply 
disappearing,  causing retransmission, as well as multiple Duplicte ACKs. Sometimes, the 
tunnel connection was actually torn down due to the error, but this happens very 
infrequently, and I suspect it depends on how mangled the packet is.

I've attached the Wireshark logs for the windows ppp interface (ftp_client) and the linux 
ftp server (ftp_server).

Oh, I also tried xl2tpd 1.0.6 and I saw the same behavior.

Hoping someone can help me with this, thanks....

Ray



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