VTY: safe version of printing VTY welcome message

The old method used raw writes to the telnet FD, which is bad for
several reasons:
  a) we don't know if we can actually write that many bytes to the
     socket at the given time
  b) the socket is still in blocking mode, so we could stall the entire
     process
  c) there may be weird interaction with the buffered writes of the
     vty_out

Now, the print_welcome() functionality has moved to vty_hello() instead,
where we can use normal vty_out() in buffered mode.

This commit is expected to fix the garbled welcome message on arm-eglibc
targets.

It might still be a good idea to migrate the entire telnet interface to
libtelnet - but at some later time ;)

2 files changed, 11 insertions, 19 deletions

diff --git a/src/vty/telnet_interface.c b/src/vty/telnet_interface.c
index 77120417..1abf141d 100644
--- a/src/vty/telnet_interface.c
+++ b/src/vty/telnet_interface.c
@@ -90,23 +90,6 @@ int telnet_init_dynif(void *tall_ctx, void *priv, const char *ip, int port)
 
 extern struct host host;
 
-static void print_welcome(int fd)
-{
-	static const char *msg1 = "Welcome to the ";
-	static const char *msg2 = " control interface\r\n";
-	const char *app_name = "<unnamed>";
-
-	if (host.app_info->name)
-		app_name = host.app_info->name;
-
-	write(fd, msg1, strlen(msg1));
-	write(fd, app_name, strlen(app_name));
-	write(fd, msg2, strlen(msg2));
-
-	if (host.app_info->copyright)
-		write(fd, host.app_info->copyright, strlen(host.app_info->copyright));
-}
-
 /*! \brief close a telnet connection */
 int telnet_close_client(struct osmo_fd *fd)
 {
@@ -169,8 +152,6 @@ static int telnet_new_connection(struct osmo_fd *fd, unsigned int what)
 	osmo_fd_register(&connection->fd);
 	llist_add_tail(&connection->entry, &active_connections);
 
-	print_welcome(new_connection);
-
 	connection->vty = vty_create(new_connection, connection);
 	if (!connection->vty) {
 		LOGP(0, LOGL_ERROR, "couldn't create VTY\n");
diff --git a/src/vty/vty.c b/src/vty/vty.c
index 04df2be0..86131ecc 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -339,6 +339,17 @@ int vty_config_unlock(struct vty *vty)
 /* Say hello to vty interface. */
 void vty_hello(struct vty *vty)
 {
+	const char *app_name = "<unnamed>";
+
+	if (host.app_info->name)
+		app_name = host.app_info->name;
+
+	vty_out(vty, "Welcome to the %s control interface%s",
+		app_name, VTY_NEWLINE);
+
+	if (host.app_info->copyright)
+		vty_out(vty, host.app_info->copyright);
+
 	if (host.motdfile) {
 		FILE *f;
 		char buf[4096];