[strongSwan] understanding libhydra kernel interface

[Ravi Kanth Vanapalli]

Hi all,

I am having trouble interpreting the plugins of libhydra, specifically
understanding the interfaces which communicate with kernel.

Scenario:* using SS client for IKEv2.*

Web link below indicates that  by default 'kernel-netlink' of libhydra will
be loaded by default for communicating with kernel net-key ipsec stack.

http://wiki.strongswan.org/projects/strongswan/wiki/Pluginlist

which means.. as per my understanding of code base.

Following would be the flow ,
*i)* ipsec start  --> starts the starter in starter.c
   There is a call  libhydra_init("starter") --> initalize kernel
interfaces specific to 'starter' for the kernel.
*iii) *Starter starts the  Charon daemon  in line 714 of starter.c.
*iii)* Inside charon.c line
       *a)* again  libhydra_init("charon")  line 472 --> initialize the
kernel interfaces ( including netlink interface) specific to the 'charon'
for the kernel
     *  b)*  line 572 Initalize the charon daemon with 'charon.load' which
reads libhydra plugins from "strongswan.conf" pertaning to "charon".

        In Step* b*) above, there is a plugin called 'kernel-netlink' which
initializes the netlink kernel interfaces for NETKEY ipsec and netlink
kernel interfaces for network. ( line 46,48 of kernel_netlink_plugin.c )

       My question is, why should we initialize the kernel interface eg.
'kernel-netlink' again when step a) already initializes the
'kernel-netlink'  interfaces in libhydra_init.

       Why should the Charon daemon specifically initalize its kernel
interfaces like in step b, when libhydra daemon for Charon..already does it
in step a.

I am not sure if my understanding or reasoning is correct and I would
deeply apppreciate any help to clarify my doubt.

Regards,
RV
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