fixes #143 Protocols and transports should be "configurable"

This makes all the protocols and transports optional.  All
of them except ZeroTier are enabled by default, but you can
now disable them (remove from the build) with cmake options.

The test suite is modified so that tests still run as much
as they can, but skip over things caused by missing functionality
from the library (due to configuration).

Further, the constant definitions and prototypes for functions
that are specific to transports or protocols are moved into
appropriate headers, which should be included directly by
applications wishing to use these.

We have also added and improved documentation -- all of the
transports are documented, and several more man pages for
protocols have been added.  (Req/Rep and Surveyor are still
missing.)

1 files changed, 34 insertions, 6 deletions

diff --git a/src/core/transport.c b/src/core/transport.c
index 6dcf4538..af9c93fb 100644
--- a/src/core/transport.c
+++ b/src/core/transport.c
@@ -10,6 +10,9 @@
 
 #include "core/nng_impl.h"
 #include "transport/inproc/inproc.h"
+#include "transport/ipc/ipc.h"
+#include "transport/tcp/tcp.h"
+#include "transport/zerotier/zerotier.h"
 
 #include <stdio.h>
 #include <string.h>
@@ -51,6 +54,11 @@ nni_tran_register(const nni_tran *tran)
 	nni_mtx_lock(&nni_tran_lk);
 	// Check to see if the transport is already registered...
 	NNI_LIST_FOREACH (&nni_tran_list, t) {
+		if (tran->tran_init == t->t_tran.tran_init) {
+			nni_mtx_unlock(&nni_tran_lk);
+			// Same transport, duplicate registration.
+			return (0);
+		}
 		if (strcmp(tran->tran_scheme, t->t_tran.tran_scheme) == 0) {
 			nni_mtx_unlock(&nni_tran_lk);
 			return (NNG_ESTATE);
@@ -129,20 +137,40 @@ nni_tran_chkopt(const char *name, const void *v, size_t sz)
 
 // nni_tran_sys_init initializes the entire transport subsystem, including
 // each individual transport.
+
+typedef int (*nni_tran_ctor)(void);
+
+static nni_tran_ctor nni_tran_ctors[] = {
+#ifdef NNG_HAVE_INPROC
+	nng_inproc_register,
+#endif
+#ifdef NNG_HAVE_IPC
+	nng_ipc_register,
+#endif
+#ifdef NNG_HAVE_TCP
+	nng_tcp_register,
+#endif
+#ifdef NNI_HAVE_ZEROTIER
+	nng_zt_register,
+#endif
+	NULL,
+};
+
 int
 nni_tran_sys_init(void)
 {
-	int rv;
+	int i;
 
 	nni_tran_inited = 1;
 	NNI_LIST_INIT(&nni_tran_list, nni_transport, t_node);
 	nni_mtx_init(&nni_tran_lk);
 
-	if (((rv = nng_inproc_register()) != 0) ||
-	    ((rv = nni_tran_register(&nni_ipc_tran)) != 0) ||
-	    ((rv = nni_tran_register(&nni_tcp_tran)) != 0)) {
-		nni_tran_sys_fini();
-		return (rv);
+	for (i = 0; nni_tran_ctors[i] != NULL; i++) {
+		int rv;
+		if ((rv = (nni_tran_ctors[i])()) != 0) {
+			nni_tran_sys_fini();
+			return (rv);
+		}
 	}
 	return (0);
 }