Merge pull request #33 from simonduq/pr/nd6-autofill

ND6 autofill

core/contiki-default-conf.h

@@ -170,10 +170,10 @@
 #define UIP_CONF_ND6_SEND_RA (NETSTACK_CONF_WITH_IPV6 && !UIP_CONF_IPV6_RPL)
 #endif /* UIP_CONF_ND6_SEND_RA */
 
-/* UIP_CONF_ND6_SEND_NS enables standard IPv6 Neighbor Discovery Protocol.
+/* UIP_CONF_ND6_SEND_NS enables standard IPv6 Neighbor Discovery Protocol
-   We enable it by default when IPv6 is used without RPL.
+   (RFC 4861). We enable it by default when IPv6 is used without RPL.
    With RPL, the neighbor cache (link-local IPv6 <-> MAC address mapping)
-   is fed whenever receiving DIO and DAO messages. This is always sufficient
+   is fed whenever receiving DIO. This is often sufficient
    for RPL routing, i.e. to send to the preferred parent or any child.
    Link-local unicast to other neighbors may, however, not be possible if
    we never receive any DIO from them. This may happen if the link from the
@@ -183,6 +183,17 @@
 #ifndef UIP_CONF_ND6_SEND_NS
 #define UIP_CONF_ND6_SEND_NS (NETSTACK_CONF_WITH_IPV6 && !UIP_CONF_IPV6_RPL)
 #endif /* UIP_CONF_ND6_SEND_NS */
+/* To speed up the neighbor cache construction,
+   enable UIP_CONF_ND6_AUTOFILL_NBR_CACHE. When a node does not the link-layer
+   address of a neighbor, it will infer it from the link-local IPv6, assuming
+   the node used autoconfiguration. Note that RPL uses its own freshness
+   mechanism to select whether neighbors are still usable as a parent
+   or not, regardless of the neighbor cache. Note that this is not
+   standard-compliant (RFC 4861), as neighbors will be added regardless of
+   their reachability and liveness. */
+#ifndef UIP_CONF_ND6_AUTOFILL_NBR_CACHE
+#define UIP_CONF_ND6_AUTOFILL_NBR_CACHE (!UIP_CONF_ND6_SEND_NS)
+#endif /* UIP_CONF_ND6_AUTOFILL_NBR_CACHE */
 /* UIP_CONF_ND6_SEND_NA allows to still comply with NDP even if the host does
    not perform NUD or DAD processes. By default it is activated so the host
    can still communicate with a full NDP peer. */

core/net/ip/tcpip.c

@@ -668,6 +668,25 @@ tcpip_ipv6_output(void)
   annotate_transmission(nexthop);
 
   nbr = uip_ds6_nbr_lookup(nexthop);
+
+#if UIP_ND6_AUTOFILL_NBR_CACHE
+  if(nbr == NULL) {
+    /* Neighbor not found in cache? Derive its link-layer address from it's
+    link-local IPv6, assuming it used autoconfiguration. This is not
+    standard-compliant but this is a convenient way to keep the
+    neighbor cache out of the way in cases ND is not used */
+    uip_lladdr_t lladdr;
+    uip_ds6_set_lladdr_from_iid(&lladdr, nexthop);
+    if((nbr = uip_ds6_nbr_add(nexthop, &lladdr,
+        0, NBR_REACHABLE, NBR_TABLE_REASON_IPV6_ND_AUTOFILL, NULL)) == NULL) {
+      PRINTF("tcpip_ipv6_output: failed to autofill neighbor cache for host ");
+      PRINT6ADDR(nexthop);
+      PRINTF("\n");
+      goto exit;
+    }
+   }
+#endif /* UIP_ND6_AUTOFILL_NBR_CACHE */
+
   if(nbr == NULL) {
     if(send_nd6_ns(nexthop)) {
       PRINTF("tcpip_ipv6_output: failed to add neighbor to cache\n");

core/net/ipv6/uip-ds6.c

@@ -558,6 +558,18 @@ uip_ds6_set_addr_iid(uip_ipaddr_t *ipaddr, uip_lladdr_t *lladdr)
 #endif
 }
 
+/*---------------------------------------------------------------------------*/
+void
+uip_ds6_set_lladdr_from_iid(uip_lladdr_t *lladdr, const uip_ipaddr_t *ipaddr)
+{
+#if (UIP_LLADDR_LEN == 8)
+  memcpy(lladdr, ipaddr->u8 + 8, UIP_LLADDR_LEN);
+  lladdr->addr[0] ^= 0x02;
+#else
+#error uip-ds6.c cannot build lladdr address when UIP_LLADDR_LEN is not 8
+#endif
+}
+
 /*---------------------------------------------------------------------------*/
 uint8_t
 get_match_length(uip_ipaddr_t *src, uip_ipaddr_t *dst)

core/net/ipv6/uip-ds6.h

@@ -344,6 +344,9 @@ uip_ds6_aaddr_t *uip_ds6_aaddr_lookup(uip_ipaddr_t *ipaddr);
 /** \brief set the last 64 bits of an IP address based on the MAC address */
 void uip_ds6_set_addr_iid(uip_ipaddr_t *ipaddr, uip_lladdr_t *lladdr);
 
+/** \brief Build a link-layer address from an IPv6 address based on its UUID64 */
+void uip_ds6_set_lladdr_from_iid(uip_lladdr_t *lladdr, const uip_ipaddr_t *ipaddr);
+
 /** \brief Get the number of matching bits of two addresses */
 uint8_t get_match_length(uip_ipaddr_t *src, uip_ipaddr_t *dst);
 

core/net/ipv6/uip-nd6.h

@@ -96,6 +96,17 @@
 #else
 #define UIP_ND6_SEND_NA UIP_CONF_ND6_SEND_NA
 #endif
+#ifndef UIP_CONF_ND6_AUTOFILL_NBR_CACHE
+/* Neighbor not found in cache? Derive its link-layer address from it's
+link-local IPv6, assuming it used autoconfiguration. This is not
+standard-compliant but this is a convenient way to keep the
+neighbor cache out of the way in cases ND is not used.
+Note that this is not standard-compliant (RFC 4861), as neighbors will
+be added regardless of their reachability and liveness.  */
+#define UIP_ND6_AUTOFILL_NBR_CACHE          0
+#else
+#define UIP_ND6_AUTOFILL_NBR_CACHE UIP_CONF_ND6_AUTOFILL_NBR_CACHE
+#endif
 #ifndef UIP_CONF_ND6_MAX_RA_INTERVAL
 #define UIP_ND6_MAX_RA_INTERVAL             600
 #else

core/net/nbr-table.h

@@ -82,6 +82,7 @@ typedef enum {
 	NBR_TABLE_REASON_RPL_DIS,
 	NBR_TABLE_REASON_ROUTE,
 	NBR_TABLE_REASON_IPV6_ND,
+  NBR_TABLE_REASON_IPV6_ND_AUTOFILL,
 	NBR_TABLE_REASON_MAC,
 	NBR_TABLE_REASON_LLSEC,
 	NBR_TABLE_REASON_LINK_STATS,