[Openswan Users] xl2tpd seems to corrupt packets

[Bartek Knapek]

I have successfully set up an Openswan 2.4.9 server with xl2tpd 1.1.12 
and pppd 2.4.4.
The setup is running on dual-cpu Linux 2.4.34 #44 SMP i686 pentium3.

I experience packets being dropped due to some problems on the l2tp-ppp 
interface.

During normal packet transfer following events occur frequently:
Jan 20 22:09:21 matylda xl2tpd[24378]: network_thread: recv packet from 
192.168.16.2, size = 665, tunnel = 54314, call = 50329 ref=0 refhim=0
Jan 20 22:09:21 matylda pppd[24419]: rcvd [LCP ProtRej id=0x8 de 6e c4 
c6 b1 bb c1 0d 64 23 bb 32 89 bd da d8 60 d7 20 d1 9e b6 d8 95 0d 1b df 
2b f4 6f e3 ce ...]
Jan 20 22:09:21 matylda pppd[24419]: Protocol-Reject for unsupported 
protocol 0xde6e
Jan 20 22:09:21 matylda xl2tpd[24378]: network_thread: recv packet from 
192.168.16.2, size = 49, tunnel = 54314, call = 50329 ref=0 refhim=0

The unsupported protocol numer seems random.
On the upper layers the packets get dropped (TCP often forced to 
re-transmit, duplicate ACKs).
There is a number of dropped packets on the ipsec interface (seems to 
increase together with the above rejects).

It seems that some packets are corrupted by xl2tpd what causes them to 
appear as LCP packets requesting an unknown protocol.

Could anyone help me fixing this?
What kind of data could I provide?
I can easily reproduce the fault (no high load necessary).

BR
Bartek