xfrm security context support

xfrm security context support

In the Linux kernel, ipsec policy and SAs can include a
security context to support MAC networking. This feature
is often referred to as "labeled ipsec".

This patchset adds security context support into ip xfrm
such that a security context can be included when
add/delete/display SAs and policies with the ip command.
The user provides the security context when adding
SAs and policies. If a policy or SA contains a security
context, the changes allow the security context to be displayed.

For example,
ip xfrm state
src 10.1.1.6 dst 10.1.1.2
	proto esp spi 0x00000301 reqid 0 mode transport
	replay-window 0
	auth hmac(digest_null) 0x3078
	enc cbc(des3_ede) 0x6970763672656164796c6f676f33646573636263696e3031
	security context root:system_r:unconfined_t:s0

Please  let me know if all is ok with the patchset.
Thanks!!

regards,
Joy

Signed-off-by:  Joy Latten <latten@austin.ibm.com>