This patch adds a multilink_join_hook for plugins to hear about
new interfaces added to a multilink bundle.

Signed-off-by: James Chapman <jchapman@katalix.com>

Index: ppp-2.4.4/pppd/auth.c
===================================================================
--- ppp-2.4.4.orig/pppd/auth.c
+++ ppp-2.4.4/pppd/auth.c
@@ -195,6 +195,11 @@ int (*null_auth_hook) __P((struct wordli
 
 int (*allowed_address_hook) __P((u_int32_t addr)) = NULL;
 
+#ifdef HAVE_MULTILINK
+/* Hook for plugin to hear when an interface joins a multilink bundle */
+void (*multilink_join_hook) __P((void)) = NULL;
+#endif
+
 /* A notifier for when the peer has authenticated itself,
    and we are proceeding to the network phase. */
 struct notifier *auth_up_notifier = NULL;
@@ -853,6 +858,9 @@ start_networks(unit)
 #ifdef HAVE_MULTILINK
     if (multilink) {
 	if (mp_join_bundle()) {
+	    if (multilink_join_hook) {
+		(*multilink_join_hook)();
+	    }
 	    if (updetach && !nodetach)
 		detach();
 	    return;
Index: ppp-2.4.4/pppd/pppd.h
===================================================================
--- ppp-2.4.4.orig/pppd/pppd.h
+++ ppp-2.4.4/pppd/pppd.h
@@ -714,6 +714,7 @@ extern void (*ip_choose_hook) __P((u_int
 
 extern int (*chap_check_hook) __P((void));
 extern int (*chap_passwd_hook) __P((char *user, char *passwd));
+extern void (*multilink_join_hook) __P((void));
 
 /* Let a plugin snoop sent and received packets.  Useful for L2TP */
 extern void (*snoop_recv_hook) __P((unsigned char *p, int len));