ipv6: Create RTF_CACHE clone when FLOWI_FLAG_KNOWN_NH is set

This patch always creates RTF_CACHE clone with DST_NOCACHE
when FLOWI_FLAG_KNOWN_NH is set so that the rt6i_dst is set to
the fl6->daddr.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Tested-by: Julian Anastasov <ja@ssi.bg>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -161,6 +161,9 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout)
 
 static inline u32 rt6_get_cookie(const struct rt6_info *rt)
 {
+	if (unlikely(rt->dst.flags & DST_NOCACHE))
+		rt = (struct rt6_info *)(rt->dst.from);
+
 	return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
 }
 

net/ipv6/route.c

@@ -901,13 +901,34 @@ redo_rt6_select:
 		}
 	}
 
-	dst_hold(&rt->dst);
+	dst_use(&rt->dst, jiffies);
 	read_unlock_bh(&table->tb6_lock);
 
-	rt6_dst_from_metrics_check(rt);
-	rt->dst.lastuse = jiffies;
-	rt->dst.__use++;
+	if (rt == net->ipv6.ip6_null_entry || (rt->rt6i_flags & RTF_CACHE)) {
+		goto done;
+	} else if (unlikely((fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH) &&
+			    !(rt->rt6i_flags & RTF_GATEWAY))) {
+		/* Create a RTF_CACHE clone which will not be
+		 * owned by the fib6 tree.  It is for the special case where
+		 * the daddr in the skb during the neighbor look-up is different
+		 * from the fl6->daddr used to look-up route here.
+		 */
+
+		struct rt6_info *uncached_rt;
+
+		uncached_rt = ip6_rt_cache_alloc(rt, &fl6->daddr, NULL);
+		dst_release(&rt->dst);
+
+		if (uncached_rt)
+			uncached_rt->dst.flags |= DST_NOCACHE;
+		else
+			uncached_rt = net->ipv6.ip6_null_entry;
+		dst_hold(&uncached_rt->dst);
+		return uncached_rt;
+	}
 
+done:
+	rt6_dst_from_metrics_check(rt);
 	return rt;
 }
 
@@ -1019,6 +1040,26 @@ static void rt6_dst_from_metrics_check(struct rt6_info *rt)
 		dst_init_metrics(&rt->dst, dst_metrics_ptr(rt->dst.from), true);
 }
 
+static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie)
+{
+	if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie))
+		return NULL;
+
+	if (rt6_check_expired(rt))
+		return NULL;
+
+	return &rt->dst;
+}
+
+static struct dst_entry *rt6_dst_from_check(struct rt6_info *rt, u32 cookie)
+{
+	if (rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
+	    rt6_check((struct rt6_info *)(rt->dst.from), cookie))
+		return &rt->dst;
+	else
+		return NULL;
+}
+
 static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
 {
 	struct rt6_info *rt;
@@ -1029,15 +1070,13 @@ static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
 	 * DST_OBSOLETE_FORCE_CHK which forces validation calls down
 	 * into this function always.
 	 */
-	if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie))
-		return NULL;
-
-	if (rt6_check_expired(rt))
-		return NULL;
 
 	rt6_dst_from_metrics_check(rt);
 
-	return dst;
+	if (unlikely(dst->flags & DST_NOCACHE))
+		return rt6_dst_from_check(rt, cookie);
+	else
+		return rt6_check(rt, cookie);
 }
 
 static struct dst_entry *ip6_negative_advice(struct dst_entry *dst)