[PATCH net-next v7 06/11] wireguard: socket: convert send{4,6} to use a noref dst when possible

[Marek Mietus <mmietus97@yahoo.com>]

send{4,6} unnecessarily reference the dst_entry from the
dst_cache when interacting with the cache.

Reduce this overhead by avoiding the redundant refcount increments.

This is only possible in flows where the cache is used. Otherwise, we
fall-back to a referenced dst.

These changes are safe as both ipv4 and ip6 support noref xmit under RCU
which is already the case for the wireguard send{4,6} functions.

Signed-off-by: Marek Mietus <mmietus97@yahoo.com>
---
 drivers/net/wireguard/socket.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireguard/socket.c b/drivers/net/wireguard/socket.c
index ee7d9c675909..b311965269a1 100644
--- a/drivers/net/wireguard/socket.c
+++ b/drivers/net/wireguard/socket.c
@@ -46,7 +46,7 @@ static int send4(struct wg_device *wg, struct sk_buff *skb,
 	fl.fl4_sport = inet_sk(sock)->inet_sport;
 
 	if (cache)
-		rt = dst_cache_get_ip4(cache, &fl.saddr);
+		rt = dst_cache_get_ip4_rcu(cache, &fl.saddr);
 
 	if (!rt) {
 		security_sk_classify_flow(sock, flowi4_to_flowi_common(&fl));
@@ -78,14 +78,15 @@ static int send4(struct wg_device *wg, struct sk_buff *skb,
 			goto err;
 		}
 		if (cache)
-			dst_cache_set_ip4(cache, &rt->dst, fl.saddr);
+			dst_cache_steal_ip4(cache, &rt->dst, fl.saddr);
 	}
 
 	skb->ignore_df = 1;
 	udp_tunnel_xmit_skb(rt, sock, skb, fl.saddr, fl.daddr, ds,
 			    ip4_dst_hoplimit(&rt->dst), 0, fl.fl4_sport,
 			    fl.fl4_dport, false, false, 0);
-	ip_rt_put(rt);
+	if (!cache)
+		ip_rt_put(rt);
 	goto out;
 
 err:
@@ -127,7 +128,7 @@ static int send6(struct wg_device *wg, struct sk_buff *skb,
 	fl.fl6_sport = inet_sk(sock)->inet_sport;
 
 	if (cache)
-		dst = dst_cache_get_ip6(cache, &fl.saddr);
+		dst = dst_cache_get_ip6_rcu(cache, &fl.saddr);
 
 	if (!dst) {
 		security_sk_classify_flow(sock, flowi6_to_flowi_common(&fl));
@@ -146,14 +147,15 @@ static int send6(struct wg_device *wg, struct sk_buff *skb,
 			goto err;
 		}
 		if (cache)
-			dst_cache_set_ip6(cache, dst, &fl.saddr);
+			dst_cache_steal_ip6(cache, dst, &fl.saddr);
 	}
 
 	skb->ignore_df = 1;
 	udp_tunnel6_xmit_skb(dst, sock, skb, skb->dev, &fl.saddr, &fl.daddr, ds,
 			     ip6_dst_hoplimit(dst), 0, fl.fl6_sport,
 			     fl.fl6_dport, false, 0);
-	dst_release(dst);
+	if (!cache)
+		dst_release(dst);
 	goto out;
 
 err:
-- 
2.51.0