diff -up dhcp-4.3.4/client/dhc6.c.PPP dhcp-4.3.4/client/dhc6.c

--- dhcp-4.3.4/client/dhc6.c.PPP	2016-04-29 12:46:29.824988665 +0200

+++ dhcp-4.3.4/client/dhc6.c	2016-04-29 12:46:29.828988666 +0200

@@ -5641,7 +5641,8 @@ make_client6_options(struct client_state

 	 */

 	if ((oc = lookup_option(&dhcpv6_universe, *op,

 				D6O_CLIENTID)) == NULL) {

-		if (!option_cache(&oc, &default_duid, NULL, clientid_option,

+		if (default_duid.len == 0 ||

+		    !option_cache(&oc, &default_duid, NULL, clientid_option,

 				  MDL))

 			log_fatal("Failure assembling a DUID.");

diff -up dhcp-4.3.4/client/dhclient.c.PPP dhcp-4.3.4/client/dhclient.c

--- dhcp-4.3.4/client/dhclient.c.PPP	2016-04-29 12:46:29.815988664 +0200

+++ dhcp-4.3.4/client/dhclient.c	2016-04-29 12:46:29.830988666 +0200

@@ -1077,8 +1077,8 @@ main(int argc, char **argv) {

 			if (default_duid.buffer != NULL)

 				data_string_forget(&default_duid, MDL);

-			form_duid(&default_duid, MDL);

-			write_duid(&default_duid);

+			if (form_duid(&default_duid, MDL) == ISC_R_SUCCESS)

+				write_duid(&default_duid);

 		}

 	}

@@ -3808,7 +3808,7 @@ write_options(struct client_state *clien

  * is not how it is intended.  Upcoming rearchitecting the client should

  * address this "one daemon model."

  */

-void

+isc_result_t

 form_duid(struct data_string *duid, const char *file, int line)

 {

 	struct interface_info *ip;

@@ -3821,6 +3821,15 @@ form_duid(struct data_string *duid, cons

 	if (ip == NULL)

 		log_fatal("Impossible condition at %s:%d.", MDL);

+	while (ip && ip->hw_address.hbuf[0] == HTYPE_RESERVED) {

+		/* Try the other interfaces */

+		log_debug("Cannot form default DUID from interface %s.", ip->name);

+		ip = ip->next;

+	}

+	if (ip == NULL) {

+		return ISC_R_UNEXPECTED;

+	}

+

 	if ((ip->hw_address.hlen == 0) ||

 	    (ip->hw_address.hlen > sizeof(ip->hw_address.hbuf)))

 		log_fatal("Impossible hardware address length at %s:%d.", MDL);

@@ -3866,6 +3875,8 @@ form_duid(struct data_string *duid, cons

 		log_info("Created duid %s.", str);

 		dfree(str, MDL);

 	}

+	

+	return ISC_R_SUCCESS;

 }

 /* Write the default DUID to the lease store. */

diff -up dhcp-4.3.4/common/bpf.c.PPP dhcp-4.3.4/common/bpf.c

--- dhcp-4.3.4/common/bpf.c.PPP	2016-04-29 12:46:29.794988660 +0200

+++ dhcp-4.3.4/common/bpf.c	2016-04-29 12:46:29.830988666 +0200

@@ -599,6 +599,22 @@ get_hw_addr(const char *name, struct har

                         memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen);

                         break;

 #endif /* IFT_FDDI */

+#if defined(IFT_PPP)

+                case IFT_PPP:

+                        if (local_family != AF_INET6)

+                             log_fatal("Unsupported device type %d for \"%s\"",

+                                        sa->sdl_type, name);

+                        hw->hlen = 0;

+                        hw->hbuf[0] = HTYPE_RESERVED;

+                        /* 0xdeadbeef should never occur on the wire,

+                         *  and is a signature that something went wrong.

+                         */

+                        hw->hbuf[1] = 0xde;

+                        hw->hbuf[2] = 0xad;

+                        hw->hbuf[3] = 0xbe;

+                        hw->hbuf[4] = 0xef;

+                        break;

+#endif

                 default:

                         log_fatal("Unsupported device type %d for \"%s\"",

                                   sa->sdl_type, name);

diff -up dhcp-4.3.4/common/lpf.c.PPP dhcp-4.3.4/common/lpf.c

--- dhcp-4.3.4/common/lpf.c.PPP	2016-03-22 14:16:51.000000000 +0100

+++ dhcp-4.3.4/common/lpf.c	2016-04-29 12:46:29.830988666 +0200

@@ -548,6 +548,22 @@ get_hw_addr(const char *name, struct har

 			hw->hbuf[0] = HTYPE_FDDI;

 			memcpy(&hw->hbuf[1], sa->sa_data, 6);

 			break;

+#if defined(ARPHRD_PPP)

+		case ARPHRD_PPP:

+			if (local_family != AF_INET6)

+				log_fatal("Unsupported device type %d for \"%s\"",

+				           sa->sa_family, name);

+			hw->hlen = 0;

+			hw->hbuf[0] = HTYPE_RESERVED;

+			/* 0xdeadbeef should never occur on the wire,

+			 * and is a signature that something went wrong.

+			 */

+			hw->hbuf[1] = 0xde;

+			hw->hbuf[2] = 0xad;

+			hw->hbuf[3] = 0xbe;

+			hw->hbuf[4] = 0xef;

+			break;

+#endif

 		default:

 			log_fatal("Unsupported device type %ld for \"%s\"",

 				  (long int)sa->sa_family, name);

diff -up dhcp-4.3.4/includes/dhcpd.h.PPP dhcp-4.3.4/includes/dhcpd.h

--- dhcp-4.3.4/includes/dhcpd.h.PPP	2016-04-29 12:46:29.831988667 +0200

+++ dhcp-4.3.4/includes/dhcpd.h	2016-04-29 12:47:13.167995959 +0200

@@ -2990,7 +2990,7 @@ void client_dns_remove(struct client_sta

 void dhcpv4_client_assignments(void);

 void dhcpv6_client_assignments(void);

-void form_duid(struct data_string *duid, const char *file, int line);

+isc_result_t form_duid(struct data_string *duid, const char *file, int line);

 void dhcp4o6_start(void);

diff -up dhcp-4.3.4/includes/dhcp.h.PPP dhcp-4.3.4/includes/dhcp.h

--- dhcp-4.3.4/includes/dhcp.h.PPP	2016-04-29 12:46:29.822988665 +0200

+++ dhcp-4.3.4/includes/dhcp.h	2016-04-29 12:46:29.832988667 +0200

@@ -81,6 +81,8 @@ struct dhcp_packet {

 					 * is no standard for this so we

 					 * just steal a type            */

+#define HTYPE_RESERVED	0		/* RFC 5494 */

+

 /* Magic cookie validating dhcp options field (and bootp vendor

    extensions field). */

 #define DHCP_OPTIONS_COOKIE	"\143\202\123\143"

diff -up dhcp-4.3.4/server/dhcpv6.c.PPP dhcp-4.3.4/server/dhcpv6.c

--- dhcp-4.3.4/server/dhcpv6.c.PPP	2016-03-22 14:16:51.000000000 +0100

+++ dhcp-4.3.4/server/dhcpv6.c	2016-04-29 12:46:29.833988667 +0200

@@ -454,6 +454,9 @@ generate_new_server_duid(void) {

 		if (p->hw_address.hlen > 0) {

 			break;

 		}

+		if (p->next == NULL && p->hw_address.hbuf[0] == HTYPE_RESERVED) {

+			log_error("Can not generate DUID from interfaces which do not have hardware addresses, please configure server-duid!");

+		}

 	}

 	if (p == NULL) {

 		return ISC_R_UNEXPECTED;