We can use this to specify 'gtp0' from openggsn, so we make sure that
it always uses the same tunnel device on creation. If it already exists,
it will return EEXIST. This is used to skip the problem of lacking
NLM_F_ECHO in the rtnetlink link interface that allows us to know the
name of the gtp device that has been dynamically allocated from the
kernel.
And, finally, I don't find any use case for having more than one tunnel
device when integrating this with openggsn.
This patch also adjusts tools/gtp-link-add.c which needs some care, since
it is not yet using any of the library functions. This tools are likely
to be useful for troubleshooting and debugging.
This patch adds the libgtpnl library. Harald mentioned that he wanted
that the specific code that is added is well encapsulated, so let's
start a small library to interact with the GTP kernel module via netlink
interface.
This was done a bit while in the rush, so the interfaces are not nice
at all and the tools need to be ported on top of this library.
This library will be used to integrate openggsn with the GTP kernel
module.
Harald Welte
Pablo Neira Ayuso