sync ppp update for new driver

README.linux

@@ -98,6 +98,8 @@ The new driver is divided into two files: ppp_generic.c and
 ppp_async.c.  The old ppp.c is still present in the kernel sources but
 is not used.  If you compile PPP as a module, you will get two
 separate modules, called ppp_generic and ppp_async.
+Another module ppp_synctty is used for synchronous tty devices
+such as high-speed WAN adapters for leased T1/E1 lines.
 
 To talk to the new driver, pppd needs to be able to open /dev/ppp,
 character device (108,0).  If the special file node /dev/ppp is not
@@ -110,6 +112,7 @@ If you use module autoloading and have PPP as a module, you will need
 to add the following to your /etc/modules.conf or /etc/conf.modules:
 
 alias tty-ldisc-3    ppp_async
+alias tty-ldisc-14   ppp_synctty
 alias char-major-108 ppp_generic
 
 

pppd/sys-linux.c

@@ -377,6 +377,13 @@ int establish_ppp (int tty_fd)
 /*
  * Set the current tty to the PPP discpline
  */
+
+#ifndef N_SYNC_PPP
+#define N_SYNC_PPP 14
+#endif
+    if (new_style_driver)
+	    ppp_disc = sync_serial ? N_SYNC_PPP:N_PPP;
+
     if (ioctl(tty_fd, TIOCSETD, &ppp_disc) < 0) {
 	if ( ! ok_error (errno) )
 	    fatal("ioctl(TIOCSETD): %m(%d)", errno);