net/tcp_states.h is not movable to include/linux/ and thus to
userspace, it defines things that are present already in existing
userland header files.  If you look, <netinet/tcp.h> defines these
state values, as an enumeration.  If you need the TCPF_* flag bit
versions, sorry... you'll need to find some other way to get those
into userspace.

The problem is that iproute ss.c needs linux/tcp.h to get the tcp_info
structure definition but linux/tcp.h has incompatible definitions with netinet/tcp.h. 
I propose that the enum be moved from net/tcp_states.h to linux/tcp.h.

-- 
Stephen Hemminger [off-list ref]