[Click] Ipsec : chatter : expensive Packet :: push; have 12 wanted 20

[ndritsos]

Hello everyone,

i'm trying to use ipsec and to run the sampler that is here:

http://www.read.cs.ucla.edu/click/examples/simple-ipsec.click


i have setup two VMs :

eth0[192.168.178.11/16] RouterONE eth1[192.168.177.24/16] 
<-------->eth1[192.168.177.1/16] RouterTWO eth0[192.168.176.1/16]

from each router i can ping the other one

in each Router i run simple-ipsec.click , with all  IP changes that it 
needs.


But it doesn't work,  The packets doesn't forward from one router to the 
other  .

i have see that when click is running ,  this element   :

  -> ipencap ::IPsecEncap  <http://www.read.cs.ucla.edu/click/elements/IPsecEncap>(50)


print this message :
chatter : expensive Packet :: push; have 12 wanted 20

Especially :

int the source  ipsec/ipsecencap.cc

this message is printed when is calling this line of code

WritablePacket *p= p_in->push( sizeof(click_ip) )

and i have checked  that the  : sizeof(click_ip) is 20

May it be  the reason that it doesn't work??
how can i fix it ?

i have see an older post :
http://pdos.csail.mit.edu/pipermail/click/2007-April/005780.html

but i don't know how to change the headroom in kernel

anyone that can help me, someone that has used ipsec , or had the same 
problem with headroom


thank you in advance


ps: i have also modified the pass and auth arguments  in 
RadixIpsecLookup( .... ) in 16 bytes and not in 32 bytes , as in 
simple-ipsec.click