[PATCH v2 net-next 3/5] ipv6: honor RT6_LOOKUP_F_DST_NOREF in rule lookup logic

[Wei Wang <tracywwnj@gmail.com>]

From: Wei Wang <weiwan@google.com>

This patch specifically converts the rule lookup logic to honor this
flag and not release refcnt when traversing each rule and calling
lookup() on each routing table.
Similar to previous patch, we also need some special handling of dst
entries in uncached list because there is always 1 refcnt taken for them
even if RT6_LOOKUP_F_DST_NOREF flag is set.

Signed-off-by: Wei Wang <weiwan@google.com>
---
 include/net/ip6_route.h | 10 ++++++++++
 net/ipv6/fib6_rules.c   | 12 +++++++-----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 82bced2fc1e3..0709835c01ad 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -94,6 +94,16 @@ static inline struct dst_entry *ip6_route_output(struct net *net,
 	return ip6_route_output_flags(net, sk, fl6, 0);
 }
 
+/* Only conditionally release dst if flags indicates
+ * !RT6_LOOKUP_F_DST_NOREF or dst is in uncached_list.
+ */
+static inline void ip6_rt_put_flags(struct rt6_info *rt, int flags)
+{
+	if (!(flags & RT6_LOOKUP_F_DST_NOREF) ||
+	    !list_empty(&rt->rt6i_uncached))
+		ip6_rt_put(rt);
+}
+
 struct dst_entry *ip6_route_lookup(struct net *net, struct flowi6 *fl6,
 				   const struct sk_buff *skb, int flags);
 struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
index bcfae13409b5..d22b6c140f23 100644
--- a/net/ipv6/fib6_rules.c
+++ b/net/ipv6/fib6_rules.c
@@ -113,14 +113,15 @@ struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
 		rt = lookup(net, net->ipv6.fib6_local_tbl, fl6, skb, flags);
 		if (rt != net->ipv6.ip6_null_entry && rt->dst.error != -EAGAIN)
 			return &rt->dst;
-		ip6_rt_put(rt);
+		ip6_rt_put_flags(rt, flags);
 		rt = lookup(net, net->ipv6.fib6_main_tbl, fl6, skb, flags);
 		if (rt->dst.error != -EAGAIN)
 			return &rt->dst;
-		ip6_rt_put(rt);
+		ip6_rt_put_flags(rt, flags);
 	}
 
-	dst_hold(&net->ipv6.ip6_null_entry->dst);
+	if (!(flags & RT6_LOOKUP_F_DST_NOREF))
+		dst_hold(&net->ipv6.ip6_null_entry->dst);
 	return &net->ipv6.ip6_null_entry->dst;
 }
 
@@ -237,13 +238,14 @@ static int __fib6_rule_action(struct fib_rule *rule, struct flowi *flp,
 			goto out;
 	}
 again:
-	ip6_rt_put(rt);
+	ip6_rt_put_flags(rt, flags);
 	err = -EAGAIN;
 	rt = NULL;
 	goto out;
 
 discard_pkt:
-	dst_hold(&rt->dst);
+	if (!(flags & RT6_LOOKUP_F_DST_NOREF))
+		dst_hold(&rt->dst);
 out:
 	res->rt6 = rt;
 	return err;
-- 
2.22.0.410.gd8fdbe21b5-goog