diff -Naur openvpn-2.1~rc7-orig/socket.c openvpn-2.1~rc7/socket.c
--- openvpn-2.1~rc7-orig/socket.c	2008-01-23 16:08:41.000000000 -0500
+++ openvpn-2.1~rc7/socket.c	2010-10-19 14:20:44.134529000 -0400
@@ -2121,11 +2121,17 @@
 
 #if ENABLE_IP_PKTINFO
 
+#ifdef __x86_64
+#pragma pack(1) /* needed to keep structure size consistent for 32 vs. 64-bit architectures */
+#endif
 struct openvpn_pktinfo
 {
   struct cmsghdr cmsghdr;
   struct in_pktinfo in_pktinfo;
 };
+#ifdef __x86_64
+#pragma pack()
+#endif
 
 static socklen_t
 link_socket_read_udp_posix_recvmsg (struct link_socket *sock,