netdev - [PATCH net-next v4 07/14] net: tunnel: make udp_tunnel{,6}_dst

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Message-ID: <20251112072720.5076-8-mmietus97@yahoo.com>
Date: Wed, 12 Nov 2025 08:27:13 +0100
From: Marek Mietus <mmietus97@...oo.com>
To: netdev@...r.kernel.org,
	sd@...asysnail.net,
	kuba@...nel.org
Cc: Marek Mietus <mmietus97@...oo.com>
Subject: [PATCH net-next v4 07/14] net: tunnel: make udp_tunnel{,6}_dst_lookup return a noref dst

Since udp_tunnel{,6}_dst_lookup return a dstref, we can avoid
incrementing the refcount on the returned dst and return a noref dst.

This only applies when CONFIG_DST_CACHE is enabled. Otherwise we
always perform an output routing lookup, which returns an owned dst.

Update udp_tunnel{,6}_dst_lookup to return a noref dst.

Signed-off-by: Marek Mietus <mmietus97@...oo.com>
---
 net/ipv4/udp_tunnel_core.c | 13 ++++++++-----
 net/ipv6/ip6_udp_tunnel.c  | 13 ++++++++-----
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/udp_tunnel_core.c b/net/ipv4/udp_tunnel_core.c
index fdfa5420f9bf..9859d6d5f521 100644
--- a/net/ipv4/udp_tunnel_core.c
+++ b/net/ipv4/udp_tunnel_core.c
@@ -240,9 +240,9 @@ int udp_tunnel_dst_lookup(struct sk_buff *skb,
 
 #ifdef CONFIG_DST_CACHE
 	if (dst_cache) {
-		rt = dst_cache_get_ip4(dst_cache, saddr);
+		rt = dst_cache_get_ip4_rcu(dst_cache, saddr);
 		if (rt) {
-			*dstref = dst_to_dstref(&rt->dst);
+			*dstref = dst_to_dstref_noref(&rt->dst);
 			return 0;
 		}
 	}
@@ -269,11 +269,14 @@ int udp_tunnel_dst_lookup(struct sk_buff *skb,
 		ip_rt_put(rt);
 		return -ELOOP;
 	}
+	*saddr = fl4.saddr;
 #ifdef CONFIG_DST_CACHE
-	if (dst_cache)
-		dst_cache_set_ip4(dst_cache, &rt->dst, fl4.saddr);
+	if (dst_cache) {
+		dst_cache_steal_ip4(dst_cache, &rt->dst, fl4.saddr);
+		*dstref = dst_to_dstref_noref(&rt->dst);
+		return 0;
+	}
 #endif
-	*saddr = fl4.saddr;
 	*dstref = dst_to_dstref(&rt->dst);
 	return 0;
 }
diff --git a/net/ipv6/ip6_udp_tunnel.c b/net/ipv6/ip6_udp_tunnel.c
index ec7bf7d744fe..e832d08b643d 100644
--- a/net/ipv6/ip6_udp_tunnel.c
+++ b/net/ipv6/ip6_udp_tunnel.c
@@ -149,9 +149,9 @@ int udp_tunnel6_dst_lookup(struct sk_buff *skb,
 
 #ifdef CONFIG_DST_CACHE
 	if (dst_cache) {
-		dst = dst_cache_get_ip6(dst_cache, saddr);
+		dst = dst_cache_get_ip6_rcu(dst_cache, saddr);
 		if (dst) {
-			*dstref = dst_to_dstref(dst);
+			*dstref = dst_to_dstref_noref(dst);
 			return 0;
 		}
 	}
@@ -177,11 +177,14 @@ int udp_tunnel6_dst_lookup(struct sk_buff *skb,
 		dst_release(dst);
 		return -ELOOP;
 	}
+	*saddr = fl6.saddr;
 #ifdef CONFIG_DST_CACHE
-	if (dst_cache)
-		dst_cache_set_ip6(dst_cache, dst, &fl6.saddr);
+	if (dst_cache) {
+		dst_cache_steal_ip6(dst_cache, dst, &fl6.saddr);
+		*dstref = dst_to_dstref_noref(dst);
+		return 0;
+	}
 #endif
-	*saddr = fl6.saddr;
 	*dstref = dst_to_dstref(dst);
 	return 0;
 }
-- 
2.51.0