From 06ff89cbe49a57781ac3fdc98a4990ebfff18f8c Mon Sep 17 00:00:00 2001
From: David van Moolenbroek <david@minix3.org>
Date: Wed, 14 Dec 2016 13:59:08 +0000
Subject: [PATCH] nd6: use default_router_list internally only

This patch rearranges the code division between nd6.c and ip6.c such
that the latter does not need to access ND6-internal data structures
(specifically, "default_router_list") directly anymore.
---
 src/core/ipv6/ip6.c    | 12 +++---------
 src/core/ipv6/nd6.c    | 25 +++++++++++++++++++++++++
 src/include/lwip/nd6.h |  2 +-
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/src/core/ipv6/ip6.c b/src/core/ipv6/ip6.c
index 0cb03182..2c2bd099 100644
--- a/src/core/ipv6/ip6.c
+++ b/src/core/ipv6/ip6.c
@@ -144,15 +144,9 @@ ip6_route(const ip6_addr_t *src, const ip6_addr_t *dest)
   }
 
   /* Get the netif for a suitable router. */
-  i = nd6_select_router(dest, NULL);
-  if (i >= 0) {
-    if (default_router_list[i].neighbor_entry != NULL) {
-      if (default_router_list[i].neighbor_entry->netif != NULL) {
-        if (netif_is_up(default_router_list[i].neighbor_entry->netif) && netif_is_link_up(default_router_list[i].neighbor_entry->netif)) {
-          return default_router_list[i].neighbor_entry->netif;
-        }
-      }
-    }
+  netif = nd6_find_route(dest);
+  if (netif != NULL && netif_is_up(netif) && netif_is_link_up(netif)) {
+    return netif;
   }
 
   /* try with the netif that matches the source address. */
diff --git a/src/core/ipv6/nd6.c b/src/core/ipv6/nd6.c
index 37b91dbb..fb4e7339 100644
--- a/src/core/ipv6/nd6.c
+++ b/src/core/ipv6/nd6.c
@@ -93,6 +93,7 @@ static void nd6_free_neighbor_cache_entry(s8_t i);
 static s8_t nd6_find_destination_cache_entry(const ip6_addr_t *ip6addr);
 static s8_t nd6_new_destination_cache_entry(void);
 static s8_t nd6_is_prefix_in_netif(const ip6_addr_t *ip6addr, struct netif *netif);
+static s8_t nd6_select_router(const ip6_addr_t *ip6addr, struct netif *netif);
 static s8_t nd6_get_router(const ip6_addr_t *router_addr, struct netif *netif);
 static s8_t nd6_new_router(const ip6_addr_t *router_addr, struct netif *netif);
 static s8_t nd6_get_onlink_prefix(ip6_addr_t *prefix, struct netif *netif);
@@ -1396,6 +1397,30 @@ nd6_select_router(const ip6_addr_t *ip6addr, struct netif *netif)
   return -1;
 }
 
+/**
+ * Find a router-announced route to the given destination.
+ *
+ * The caller is responsible for checking whether the returned netif, if any,
+ * is in a suitable state (up, link up) to be used for packet transmission.
+ *
+ * @param ip6addr the destination IPv6 address
+ * @return the netif to use for the destination, or NULL if none found
+ */
+struct netif *
+nd6_find_route(const ip6_addr_t *ip6addr)
+{
+  s8_t i;
+
+  i = nd6_select_router(ip6addr, NULL);
+  if (i >= 0) {
+    if (default_router_list[i].neighbor_entry != NULL) {
+      return default_router_list[i].neighbor_entry->netif; /* may be NULL */
+    }
+  }
+
+  return NULL;
+}
+
 /**
  * Find an entry for a default router.
  *
diff --git a/src/include/lwip/nd6.h b/src/include/lwip/nd6.h
index e6e2d9c1..1d4b2f26 100644
--- a/src/include/lwip/nd6.h
+++ b/src/include/lwip/nd6.h
@@ -143,7 +143,7 @@ void nd6_tmr(void);
 void nd6_input(struct pbuf *p, struct netif *inp);
 void nd6_clear_destination_cache(void);
 s8_t nd6_get_next_hop_entry(const ip6_addr_t *ip6addr, struct netif *netif);
-s8_t nd6_select_router(const ip6_addr_t *ip6addr, struct netif *netif);
+struct netif *nd6_find_route(const ip6_addr_t *ip6addr);
 u16_t nd6_get_destination_mtu(const ip6_addr_t *ip6addr, struct netif *netif);
 err_t nd6_queue_packet(s8_t neighbor_index, struct pbuf *p);
 #if LWIP_ND6_TCP_REACHABILITY_HINTS