From 828173483886990474f217910ebe02583674f0e8 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@samba.org>
Date: Tue, 14 Dec 1993 05:16:01 +0000
Subject: [PATCH] check if we have ppp early on

---
 pppd/main.c    |  7 ++++++-
 pppd/sys-str.c | 21 ++++++++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/pppd/main.c b/pppd/main.c
index 4e1e3de..30596d1 100644
--- a/pppd/main.c
+++ b/pppd/main.c
@@ -18,7 +18,7 @@
  */
 
 #ifndef lint
-static char rcsid[] = "$Id: main.c,v 1.2 1993/11/23 23:40:53 paulus Exp $";
+static char rcsid[] = "$Id: main.c,v 1.3 1993/12/14 05:16:01 paulus Exp $";
 #endif
 
 #define SETSID
@@ -223,6 +223,11 @@ main(argc, argv)
 
     pid = getpid();
 
+    if (!ppp_available()) {
+	fprintf(stderr, "Sorry - PPP is not available on this system\n");
+	exit(1);
+    }
+
     /*
      * Initialize to the standard option set, then parse, in order,
      * the system options file, the user's options file, and the command
diff --git a/pppd/sys-str.c b/pppd/sys-str.c
index ecee95b..6bd2fc9 100644
--- a/pppd/sys-str.c
+++ b/pppd/sys-str.c
@@ -22,8 +22,10 @@
  * TODO:
  */
 
+#include <stdio.h>
 #include <errno.h>
 #include <syslog.h>
+#include <fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -50,7 +52,24 @@ static struct	modlist {
 } str_modules[MAXMODULES];
 static int	str_module_count = 0;
 
-extern int hungup;
+extern int hungup;		/* has the physical layer been disconnected? */
+
+/*
+ * ppp_available - check if this kernel supports PPP.
+ */
+int
+ppp_available()
+{
+    int fd, ret;
+
+    fd = open("/dev/tty", O_RDONLY, 0);
+    if (fd < 0)
+	return 1;		/* can't find out - assume we have ppp */
+    ret = ioctl(fd, I_FIND, "pppasync") >= 0;
+    close(fd);
+    return ret;
+}
+
 
 /*
  * establish_ppp - Turn the serial port into a ppp interface.
-- 
2.39.2