netdev - [PATCH net-next 3/5] net: add skb_set_owner

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Message-ID: <20241004191644.1687638-4-edumazet@google.com>
Date: Fri,  4 Oct 2024 19:16:42 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Martin KaFai Lau <martin.lau@...ux.dev>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 3/5] net: add skb_set_owner_edemux() helper

This can be used to attach a socket to an skb,
taking a reference on sk->sk_refcnt.

This helper might be a NOP if sk->sk_refcnt is zero.

Use it from tcp_make_synack().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sock.h    | 9 +++++++++
 net/core/sock.c       | 9 +++------
 net/ipv4/tcp_output.c | 2 +-
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index c868b8b57e3489cd81efafa3856da09397059080..5facbf33316ab0a424b320850198c7cd6bc1a642 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1752,6 +1752,15 @@ void sock_efree(struct sk_buff *skb);
 #ifdef CONFIG_INET
 void sock_edemux(struct sk_buff *skb);
 void sock_pfree(struct sk_buff *skb);
+
+static inline void skb_set_owner_edemux(struct sk_buff *skb, struct sock *sk)
+{
+	skb_orphan(skb);
+	if (refcount_inc_not_zero(&sk->sk_refcnt)) {
+		skb->sk = sk;
+		skb->destructor = sock_edemux;
+	}
+}
 #else
 #define sock_edemux sock_efree
 #endif
diff --git a/net/core/sock.c b/net/core/sock.c
index 039be95c40cf6fa429d33e0f42ee606188045992..0582306bb576291c43c9eb0700130b36ba44cc25 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2594,14 +2594,11 @@ void __sock_wfree(struct sk_buff *skb)
 void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
 {
 	skb_orphan(skb);
-	skb->sk = sk;
 #ifdef CONFIG_INET
-	if (unlikely(!sk_fullsock(sk))) {
-		skb->destructor = sock_edemux;
-		sock_hold(sk);
-		return;
-	}
+	if (unlikely(!sk_fullsock(sk)))
+		return skb_set_owner_edemux(skb, sk);
 #endif
+	skb->sk = sk;
 	skb->destructor = sock_wfree;
 	skb_set_hash_from_sk(skb, sk);
 	/*
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4fd746bd4d54f621601b20c3821e71370a4a615a..60c16fa4c9007006ff8ba49b695d227652a2eafb 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3731,7 +3731,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 
 	switch (synack_type) {
 	case TCP_SYNACK_NORMAL:
-		skb_set_owner_w(skb, req_to_sk(req));
+		skb_set_owner_edemux(skb, req_to_sk(req));
 		break;
 	case TCP_SYNACK_COOKIE:
 		/* Under synflood, we do not attach skb to a socket,
-- 
2.47.0.rc0.187.ge670bccf7e-goog