Adjust tcp_client.py and tcp_server.py to work with Python 3 by using
the print function, marking string literals as bytes, and using the
newer exception syntax. This should be functionally equivalent and
supports Python 3+.

Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Added a selftest for tcpbpf (sock_ops) that checks that the appropriate
callbacks occured and that it can access tcp_sock fields and that their
values are correct.

Run with command: ./test_tcpbpf_user
Adding the flag "-d" will show why it did not pass.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>