diff -up pptp-1.7.2/pptp_gre.c.nested pptp-1.7.2/pptp_gre.c
--- pptp-1.7.2/pptp_gre.c.nested	2011-12-06 16:45:34.605691678 +0000
+++ pptp-1.7.2/pptp_gre.c	2011-12-06 19:07:14.169449813 +0000
@@ -23,6 +23,10 @@
 #include "pqueue.h"
 #include "test.h"
 
+/* globals from pptp.c */
+extern struct in_addr localbind;
+extern int rtmark;
+
 #define PACKET_MAX 8196
 /* test for a 32 bit counter overflow */
 #define WRAPPED( curseq, lastseq) \
@@ -82,7 +86,6 @@ uint64_t time_now_usecs(void)
 int pptp_gre_bind(struct in_addr inetaddr)
 {
     struct sockaddr_in src_addr, loc_addr;
-    extern struct in_addr localbind;
     int s = socket(AF_INET, SOCK_RAW, PPTP_PROTO);
     if (s < 0) { warn("socket: %s", strerror(errno)); return -1; }
     if (localbind.s_addr != INADDR_NONE) {