--- busybox.org/networking/ifupdown.c	2015-08-28 16:39:31.840093464 +0800
+++ busybox/networking/ifupdown.c	2015-08-28 16:39:46.991944891 +0800
@@ -46,6 +46,9 @@
 #include "libbb.h"
 /* After libbb.h, since it needs sys/types.h on some systems */
 #include <sys/utsname.h>
+#include <sys/socket.h>
+#include <linux/if_arp.h>
+#include <arpa/inet.h>
 #include <fnmatch.h>
 
 #define MAX_OPT_DEPTH 10
@@ -108,6 +111,22 @@
 	struct mapping_defn_t *mappings;
 };
 
+/*IPv6 DUID*/
+#define DUID_FILE "/conf/dhcp6c_duid"
+#define MAC_ADDR_LEN	6
+
+/* DUID: DHCP unique Identifier */
+struct duid {
+	size_t duid_len;	/* length */
+	char *duid_id;		/* variable length ID value (must be opaque) */
+};
+
+/* DUID type 3 */
+struct dhcp6opt_duid_type3 {
+        u_int16_t dh6_duid1_type;
+        u_int16_t dh6_duid1_hwtype;
+        /* link-layer address follows */
+} __attribute__ ((__packed__));
 
 #define OPTION_STR "anvf" IF_FEATURE_IFUPDOWN_MAPPING("m") "i:"
 enum {
@@ -413,10 +432,120 @@
 # endif
 }
 
+static ssize_t
+gethwid(buf, len, ifname, hwtypep)
+	char *buf;
+	int len;
+	const char *ifname;
+	u_int16_t *hwtypep;
+{
+	int fd;
+	struct ifreq ifr;
+	ssize_t l;
+
+	memset(&ifr, 0, sizeof(ifr));
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+
+	ifr.ifr_addr.sa_family = AF_INET;
+	strncpy(ifr.ifr_name, ifname, IFNAMSIZ-1);
+
+	if (ioctl(fd, SIOCGIFHWADDR, &ifr) != -1) {
+		#if 0
+        printf("Mac address: %02x:%02x:%02x:%02x:%02x:%02x\n",
+                (unsigned char)ifr.ifr_hwaddr.sa_data[0],
+                (unsigned char)ifr.ifr_hwaddr.sa_data[1],
+                (unsigned char)ifr.ifr_hwaddr.sa_data[2],
+                (unsigned char)ifr.ifr_hwaddr.sa_data[3],
+                (unsigned char)ifr.ifr_hwaddr.sa_data[4],
+                (unsigned char)ifr.ifr_hwaddr.sa_data[5]);
+		#endif
+    }
+	close(fd);
+
+	memcpy(buf, &ifr.ifr_hwaddr.sa_data, MAC_ADDR_LEN);	
+	
+	*hwtypep = ARPHRD_ETHER;
+	l = MAC_ADDR_LEN;
+		
+	return (l);	
+}
+
+int Refresh_DUID(ifname, duid)
+	char *ifname;
+	struct duid *duid;
+{
+	FILE *fp = NULL;
+	u_int16_t len = 0, hwtype;
+	struct dhcp6opt_duid_type3 *dp; /* we only support the type3 DUID */	
+	char tmpbuf[256];	/* DUID should be no more than 256 bytes */
+	int l,i;
+	
+	if ((l = gethwid(tmpbuf, sizeof(tmpbuf), ifname , &hwtype)) < 0) {
+		goto fail;
+	}
+	len = l + sizeof(struct dhcp6opt_duid_type3);
+		
+	memset(duid, 0, sizeof(*duid));
+	duid->duid_len = len;
+	
+	if ((duid->duid_id = (char *)malloc(len)) == NULL) {
+		printf("failed to allocate memory\n");
+		goto fail;
+	}
+	
+	/* copy (and fill) the ID */
+	dp = (struct dhcp6opt_duid_type3 *)duid->duid_id;
+	dp->dh6_duid1_type = htons(3); /* type 1 */
+	dp->dh6_duid1_hwtype = htons(hwtype);	
+	memcpy((void *)(dp + 1), tmpbuf, (len - sizeof(*dp)));
+ 	
+	for(i = 0 ; i < (len - sizeof(*dp)); i++){
+			//printf("%2x ",tmpbuf[i]);
+	}
+
+	/* save the (new) ID to the file for next time */
+	if (!fp) {
+		if ((fp = fopen(DUID_FILE, "w+")) == NULL) {
+			printf("failed to open DUID file for save\n");
+			goto fail;
+		}
+		if ((fwrite(&len, sizeof(len), 1, fp)) != 1) {
+			printf("failed to save DUID\n");
+			goto fail;
+		}
+
+		if ((fwrite(duid->duid_id, len, 1, fp)) != 1) {
+			printf("failed to save DUID\n");
+			goto fail;
+		}
+	}
+
+	if (fp)
+		fclose(fp);	
+	if (duid->duid_id) {
+		free(duid->duid_id);
+		duid->duid_id = NULL; /* for safety */
+	}
+    return 0;
+
+    fail:
+		if (fp)
+			fclose(fp);
+		if (duid->duid_id) {
+			free(duid->duid_id);
+			duid->duid_id = NULL; /* for safety */
+		}		
+		return (-1);    
+}
 
 static int FAST_FUNC dhcp_up6(struct interface_defn_t *ifd, execfn *exec)
 {
 	int result = 0;
+	static struct duid client_duid;
+
+    //refresh /conf/dhcp6c_duid
+    Refresh_DUID(ifd->iface, &client_duid);	
+
     if (!execute("ifconfig %iface%[[ hw %hwaddress%]] up", ifd, exec))
         return 0;