tls: kernel TLS support

Software implementation of transport layer security, implemented using ULP
infrastructure.  tcp proto_ops are replaced with tls equivalents of sendmsg and
sendpage.

Only symmetric crypto is done in the kernel, keys are passed by setsockopt
after the handshake is complete.  All control messages are supported via CMSG
data - the actual symmetric encryption is the same, just the message type needs
to be passed separately.

For user API, please see Documentation patch.

Pieces that can be shared between hw and sw implementation
are in tls_main.c

Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
Signed-off-by: Aviad Yehezkel <aviadye@mellanox.com>
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/Kconfig

@@ -0,0 +1,12 @@
+#
+# TLS configuration
+#
+config TLS
+	tristate "Transport Layer Security support"
+	depends on NET
+	default m
+	---help---
+	Enable kernel support for TLS protocol. This allows symmetric
+	encryption handling of the TLS protocol to be done in-kernel.
+
+	If unsure, say M.