node: align Node::getPollFDs() with Node::getNetemFDs()

include/villas/node.hpp

@@ -237,9 +237,9 @@ public:
 	}
 
 	virtual
-	int getNetemFDs(int fds[])
+	std::vector<int> getNetemFDs()
 	{
-		return 0;
+		return {};
 	}
 
 	virtual

include/villas/node_compat.hpp

@@ -166,7 +166,7 @@ public:
 	 * @return The number of file descriptors which have been put into \p sds.
 	 */
 	virtual
-	int getNetemFDs(int fds[]);
+	std::vector<int> getNetemFDs();
 
 	/** Return a memory allocator which should be used for sample pools passed to this node. */
 	virtual

lib/node.cpp

@@ -254,12 +254,7 @@ int Node::start()
 #ifdef __linux__
 	/* Set fwmark for outgoing packets if netem is enabled for this node */
 	if (fwmark >= 0) {
-		int fds[16];
-		int num_sds = getNetemFDs(fds);
-
-		for (int i = 0; i < num_sds; i++) {
-			int fd = fds[i];
-
+		for (auto fd : getNetemFDs()) {
 			ret = setsockopt(fd, SOL_SOCKET, SO_MARK, &fwmark, sizeof(fwmark));
 			if (ret)
 				throw RuntimeError("Failed to set FW mark for outgoing packets");

lib/node_compat.cpp

@@ -217,11 +217,19 @@ std::vector<int> NodeCompat::getPollFDs()
 	return {};
 }
 
-int NodeCompat::getNetemFDs(int fds[])
+std::vector<int> NodeCompat::getNetemFDs()
 {
-	return _vt->netem_fds
-		? _vt->netem_fds(this, fds)
-		: -1;
+	if (_vt->netem_fds) {
+		int ret, fds[16];
+
+		ret = _vt->netem_fds(this, fds);
+		if (ret < 0)
+			return {};
+
+		return std::vector<int>(fds, fds+ret);
+	}
+
+	return {};
 }
 
 struct memory::Type * NodeCompat::getMemoryType()