pppd: Allow specifying ipv6-up and ipv6-down scripts

This patch implements the "ipv6-up-script" and "ipv6-down-script" options
which allow to specify the path of the ipv6-up and ipv6-down scripts to call.

These options default to _PATH_IPV6UP and _PATH_IPV6DOWN to retain the
existing behaviour.

The patch originated from the Debian project.

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

--- a/pppd/main.c
+++ b/pppd/main.c
@@ -318,6 +318,8 @@ main(argc, argv)
 
     strlcpy(path_ipup, _PATH_IPUP, sizeof(path_ipup));
     strlcpy(path_ipdown, _PATH_IPDOWN, sizeof(path_ipdown));
+    strlcpy(path_ipv6up, _PATH_IPV6UP, sizeof(path_ipv6up));
+    strlcpy(path_ipv6down, _PATH_IPV6DOWN, sizeof(path_ipv6down));
 
     link_stats_valid = 0;
     new_phase(PHASE_INITIALIZE);
--- a/pppd/options.c
+++ b/pppd/options.c
@@ -116,6 +116,8 @@ int	connect_delay = 1000;	/* wait this m
 int	req_unit = -1;		/* requested interface unit */
 char	path_ipup[MAXPATHLEN];	/* pathname of ip-up script */
 char	path_ipdown[MAXPATHLEN];/* pathname of ip-down script */
+char	path_ipv6up[MAXPATHLEN];	/* pathname of ipv6-up script */
+char	path_ipv6down[MAXPATHLEN];/* pathname of ipv6-down script */
 bool	multilink = 0;		/* Enable multilink operation */
 char	*bundle_name = NULL;	/* bundle name for multilink */
 bool	dump_options;		/* print out option values */
@@ -308,6 +310,13 @@ option_t general_options[] = {
       "Set pathname of ip-down script",
       OPT_PRIV|OPT_STATIC, NULL, MAXPATHLEN },
 
+    { "ipv6-up-script", o_string, path_ipv6up,
+      "Set pathname of ipv6-up script",
+      OPT_PRIV|OPT_STATIC, NULL, MAXPATHLEN },
+    { "ipv6-down-script", o_string, path_ipv6down,
+      "Set pathname of ipv6-down script",
+      OPT_PRIV|OPT_STATIC, NULL, MAXPATHLEN },
+
 #ifdef HAVE_MULTILINK
     { "multilink", o_bool, &multilink,
       "Enable multilink operation", OPT_PRIO | 1 },
--- a/pppd/ipv6cp.c
+++ b/pppd/ipv6cp.c
@@ -1269,7 +1269,7 @@ ipv6cp_up(f)
      */
     if (ipv6cp_script_state == s_down && ipv6cp_script_pid == 0) {
 	ipv6cp_script_state = s_up;
-	ipv6cp_script(_PATH_IPV6UP);
+	ipv6cp_script(path_ipv6up);
     }
 }
 
@@ -1321,7 +1321,7 @@ ipv6cp_down(f)
     /* Execute the ipv6-down script */
     if (ipv6cp_script_state == s_up && ipv6cp_script_pid == 0) {
 	ipv6cp_script_state = s_down;
-	ipv6cp_script(_PATH_IPV6DOWN);
+	ipv6cp_script(path_ipv6down);
     }
 }
 
@@ -1364,13 +1364,13 @@ ipv6cp_script_done(arg)
     case s_up:
 	if (ipv6cp_fsm[0].state != OPENED) {
 	    ipv6cp_script_state = s_down;
-	    ipv6cp_script(_PATH_IPV6DOWN);
+	    ipv6cp_script(path_ipv6down);
 	}
 	break;
     case s_down:
 	if (ipv6cp_fsm[0].state == OPENED) {
 	    ipv6cp_script_state = s_up;
-	    ipv6cp_script(_PATH_IPV6UP);
+	    ipv6cp_script(path_ipv6up);
 	}
 	break;
     }
--- a/pppd/pppd.h
+++ b/pppd/pppd.h
@@ -320,6 +320,8 @@ extern int	max_data_rate;	/* max bytes/s
 extern int	req_unit;	/* interface unit number to use */
 extern char	path_ipup[MAXPATHLEN]; /* pathname of ip-up script */
 extern char	path_ipdown[MAXPATHLEN]; /* pathname of ip-down script */
+extern char	path_ipv6up[MAXPATHLEN]; /* pathname of ipv6-up script */
+extern char	path_ipv6down[MAXPATHLEN]; /* pathname of ipv6-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 */