fixes #39 Transport ops vector should be versioned

This also includes tests for some of the edge cases surrounding
pluggable transports, such as version mismatch, duplication registration,
and failure to initialize.

2 files changed, 33 insertions, 1 deletions

diff --git a/src/core/transport.c b/src/core/transport.c
index 6f73a6b2..2f373f9a 100644
--- a/src/core/transport.c
+++ b/src/core/transport.c
@@ -27,6 +27,7 @@ typedef struct nni_transport {
 
 static nni_list nni_tran_list;
 static nni_mtx  nni_tran_lk;
+static int      nni_tran_inited;
 
 int
 nni_tran_register(const nni_tran *tran)
@@ -34,6 +35,18 @@ nni_tran_register(const nni_tran *tran)
 	nni_transport *t;
 	int            rv;
 
+	// Its entirely possible that we are called before any sockets
+	// are opened.  Make sure we are initialized.  This has to be
+	// protected by a guard to prevent infinite recursion, since
+	// nni_init also winds up calling us.
+	if (!nni_tran_inited) {
+		nni_init();
+	}
+
+	if (tran->tran_version != NNI_TRANSPORT_VERSION) {
+		return (NNG_ENOTSUP);
+	}
+
 	nni_mtx_lock(&nni_tran_lk);
 	// Check to see if the transport is already registered...
 	NNI_LIST_FOREACH (&nni_tran_list, t) {
@@ -83,6 +96,7 @@ nni_tran_sys_init(void)
 {
 	int rv;
 
+	nni_tran_inited = 1;
 	NNI_LIST_INIT(&nni_tran_list, nni_transport, t_node);
 	nni_mtx_init(&nni_tran_lk);
 
@@ -108,4 +122,5 @@ nni_tran_sys_fini(void)
 		NNI_FREE_STRUCT(t);
 	}
 	nni_mtx_fini(&nni_tran_lk);
+	nni_tran_inited = 0;
 }
diff --git a/src/core/transport.h b/src/core/transport.h
index 11cdcf99..78cb2bbf 100644
--- a/src/core/transport.h
+++ b/src/core/transport.h
@@ -1,5 +1,6 @@
 //
-// Copyright 2016 Garrett D'Amore <garrett@damore.org>
+// Copyright 2017 Garrett D'Amore <garrett@damore.org>
+// Copyright 2017 Capitar IT Group BV <info@capitar.com>
 //
 // This software is supplied under the terms of the MIT License, a
 // copy of which should be located in the distribution where this
@@ -14,6 +15,11 @@
 // interfaces in this file.
 
 struct nni_tran {
+	// tran_version is the version of the transport ops that this
+	// transport implements.  We only bother to version the main
+	// ops vector.
+	uint32_t tran_version;
+
 	// tran_scheme is the transport scheme, such as "tcp" or "inproc".
 	const char *tran_scheme;
 
@@ -32,6 +38,17 @@ struct nni_tran {
 	void (*tran_fini)(void);
 };
 
+// We quite intentionally use a signature where the upper word is nonzero,
+// which ensures that if we get garbage we will reject it.  This is more
+// likely to mismatch than all zero bytes would.  The actual version is
+// stored in the lower word; this is not semver -- the numbers are just
+// increasing - we doubt it will increase more than a handful of times
+// during the life of the project.  If we add a new version, please keep
+// the old version around -- it may be possible to automatically convert
+// older versions in the future.
+#define NNI_TRANSPORT_V0 0x54520000
+#define NNI_TRANSPORT_VERSION NNI_TRANSPORT_V0
+
 // Endpoint operations are called by the socket in a protocol-independent
 // fashion.  The socket makes individual calls, which are expected to block
 // if appropriate (except for destroy). Endpoints are unable to call back