Introduce DTLS transport for NNG.

This introduces a new experimental transport for DTLS, that
provides encryption over UDP.  It has a simpler protocol than
the current UDP SP protocol (but we intend to fix that by making
the UDP transport simpler in a follow up!)

There are a few other fixes in the TLS layer itself, and in
the build, that were needed to accomplish this work.

Also there was an endianness bug in the UDP protocol handling, which
is fixed here.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/sp/transport.h b/src/sp/transport.h
index 9d67b7c2..6aa2086b 100644
--- a/src/sp/transport.h
+++ b/src/sp/transport.h
@@ -139,7 +139,12 @@ struct nni_sp_pipe_ops {
 	// p_init initializes the pipe data structures.  The main
 	// purpose of this is so that the pipe will see the upper
 	// layer nni_pipe and get a chance to register stats and such.
-	size_t p_size;
+	// size_t p_size;
+
+	// p_size returns the size of the transport data needed for a pipe.
+	// This allows for dynamic registration of context size to allow for
+	// different tunings or different runtimes.
+	size_t (*p_size)(void);
 
 	// p_init initializes the transport's pipe data structure.
 	// The pipe MUST be left in a state that p_fini can be safely