netdev - [PATCH RFC 2/9] sk_buff: track dst status in skb->

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Message-Id: <596f20dc9e8b0cb0394c0f64fa8ce968c0187047.1626882513.git.pabeni@redhat.com>
Date:   Wed, 21 Jul 2021 18:44:34 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Westphal <fw@...len.de>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Subject: [PATCH RFC 2/9] sk_buff: track dst status in skb->_state

Similar to the previous patch, covering the dst field,
but limited to tracking only the dst status.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 include/linux/skbuff.h | 4 ++++
 include/net/dst.h      | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ec3d34d8022f..1b811585f6fc 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -691,6 +691,7 @@ typedef unsigned char *sk_buff_data_t;
  *	@decrypted: Decrypted SKB
  *	@_state: bitmap reporting the presence of some skb state info
  *	@has_nfct: @_state bit for nfct info
+ *	@has_dst: @_state bit for dst pointer
  *	@napi_id: id of the NAPI struct this skb came from
  *	@sender_cpu: (aka @napi_id) source CPU in XPS
  *	@secmark: security marking
@@ -873,6 +874,7 @@ struct sk_buff {
 		__u8		_state;		/* state of extended fields */
 		struct {
 			__u8	has_nfct:1;
+			__u8	has_dst:1;
 		};
 	};
 
@@ -998,6 +1000,7 @@ static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
  */
 static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
 {
+	skb->has_dst = !!dst;
 	skb->_skb_refdst = (unsigned long)dst;
 }
 
@@ -1014,6 +1017,7 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
 static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
 {
 	WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
+	skb->has_dst = !!dst;
 	skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
 }
 
diff --git a/include/net/dst.h b/include/net/dst.h
index 75b1e734e9c2..2cb765dabc6f 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -272,11 +272,13 @@ static inline void skb_dst_drop(struct sk_buff *skb)
 	if (skb->_skb_refdst) {
 		refdst_drop(skb->_skb_refdst);
 		skb->_skb_refdst = 0UL;
+		skb->has_dst = 0;
 	}
 }
 
 static inline void __skb_dst_copy(struct sk_buff *nskb, unsigned long refdst)
 {
+	nskb->has_dst = !!refdst;
 	nskb->_skb_refdst = refdst;
 	if (!(nskb->_skb_refdst & SKB_DST_NOREF))
 		dst_clone(skb_dst(nskb));
@@ -316,6 +318,7 @@ static inline bool skb_dst_force(struct sk_buff *skb)
 			dst = NULL;
 
 		skb->_skb_refdst = (unsigned long)dst;
+		skb->has_dst = !!dst;
 	}
 
 	return skb->_skb_refdst != 0UL;
-- 
2.26.3