pppd: Allow specifying ip-up and ip-down scripts

This patch implements the "ip-up-script" and "ip-down-script" options which
allow to specify the path of the ip-up and ip-down scripts to call.

These options default to _PATH_IPUP and _PATH_IPDOWN to retain the 
existing behaviour.

The patch originated from the Debian project.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

--- a/pppd/ipcp.c
+++ b/pppd/ipcp.c
@@ -1957,7 +1957,7 @@ ipcp_up(f)
      */
     if (ipcp_script_state == s_down && ipcp_script_pid == 0) {
 	ipcp_script_state = s_up;
-	ipcp_script(_PATH_IPUP, 0);
+	ipcp_script(path_ipup, 0);
     }
 }
 
@@ -2007,7 +2007,7 @@ ipcp_down(f)
     /* Execute the ip-down script */
     if (ipcp_script_state == s_up && ipcp_script_pid == 0) {
 	ipcp_script_state = s_down;
-	ipcp_script(_PATH_IPDOWN, 0);
+	ipcp_script(path_ipdown, 0);
     }
 }
 
@@ -2061,13 +2061,13 @@ ipcp_script_done(arg)
     case s_up:
 	if (ipcp_fsm[0].state != OPENED) {
 	    ipcp_script_state = s_down;
-	    ipcp_script(_PATH_IPDOWN, 0);
+	    ipcp_script(path_ipdown, 0);
 	}
 	break;
     case s_down:
 	if (ipcp_fsm[0].state == OPENED) {
 	    ipcp_script_state = s_up;
-	    ipcp_script(_PATH_IPUP, 0);
+	    ipcp_script(path_ipup, 0);
 	}
 	break;
     }
--- a/pppd/main.c
+++ b/pppd/main.c
@@ -306,6 +306,9 @@ main(argc, argv)
     struct protent *protp;
     char numbuf[16];
 
+    strlcpy(path_ipup, _PATH_IPUP, sizeof(path_ipup));
+    strlcpy(path_ipdown, _PATH_IPDOWN, sizeof(path_ipdown));
+
     link_stats_valid = 0;
     new_phase(PHASE_INITIALIZE);
 
--- a/pppd/options.c
+++ b/pppd/options.c
@@ -117,6 +117,8 @@ bool	tune_kernel;		/* may alter kernel s
 int	connect_delay = 1000;	/* wait this many ms after connect script */
 int	req_unit = -1;		/* requested interface unit */
 char	req_ifname[MAXIFNAMELEN];	/* requested interface name */
+char	path_ipup[MAXPATHLEN];	/* pathname of ip-up script */
+char	path_ipdown[MAXPATHLEN];/* pathname of ip-down script */
 bool	multilink = 0;		/* Enable multilink operation */
 char	*bundle_name = NULL;	/* bundle name for multilink */
 bool	dump_options;		/* print out option values */
@@ -316,6 +318,13 @@ option_t general_options[] = {
       "Metric to use for the default route (Linux only; -1 for default behavior)",
       OPT_PRIV|OPT_LLIMIT|OPT_INITONLY, NULL, 0, -1 },
 
+    { "ip-up-script", o_string, path_ipup,
+      "Set pathname of ip-up script",
+      OPT_PRIV|OPT_STATIC, NULL, MAXPATHLEN },
+    { "ip-down-script", o_string, path_ipdown,
+      "Set pathname of ip-down script",
+      OPT_PRIV|OPT_STATIC, NULL, MAXPATHLEN },
+
 #ifdef HAVE_MULTILINK
     { "multilink", o_bool, &multilink,
       "Enable multilink operation", OPT_PRIO | 1 },
--- a/pppd/pppd.h
+++ b/pppd/pppd.h
@@ -332,6 +332,8 @@ extern int	connect_delay;	/* Time to del
 extern int	max_data_rate;	/* max bytes/sec through charshunt */
 extern int	req_unit;	/* interface unit number to use */
 extern char	req_ifname[MAXIFNAMELEN]; /* interface name to use */
+extern char	path_ipup[MAXPATHLEN]; /* pathname of ip-up script */
+extern char	path_ipdown[MAXPATHLEN]; /* pathname of ip-down script */
 extern bool	multilink;	/* enable multilink operation */
 extern bool	noendpoint;	/* don't send or accept endpt. discrim. */
 extern char	*bundle_name;	/* bundle name for multilink */