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From: Cong Wang <xiyou.wangcong@gmail.com>
To: netdev@vger.kernel.org
Cc: bpf@vger.kernel.org, duanxiongchun@bytedance.com,
	wangdongdong.6@bytedance.com, jiang.wang@bytedance.com,
	Cong Wang <cong.wang@bytedance.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jakub Sitnicki <jakub@cloudflare.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	John Fastabend <john.fastabend@gmail.com>
Subject: [Patch bpf-next v6 4/8] skmsg: move sk_redir from TCP_SKB_CB to skb
Date: Fri, 19 Feb 2021 21:29:20 -0800
Message-ID: <20210220052924.106599-5-xiyou.wangcong@gmail.com> (raw)
In-Reply-To: <20210220052924.106599-1-xiyou.wangcong@gmail.com>

From: Cong Wang <cong.wang@bytedance.com>

Currently TCP_SKB_CB() is hard-coded in skmsg code, it certainly
does not work for any other non-TCP protocols. We can move them to
skb ext, but it introduces a memory allocation on fast path.

Fortunately, we only need to a word-size to store all the information,
because the flags actually only contains 1 bit so can be just packed
into the lowest bit of the "pointer", which is stored as unsigned
long.

Inside struct sk_buff, '_skb_refdst' can be reused because skb dst is
no longer needed after ->sk_data_ready() so we can just drop it.

Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
 include/linux/skbuff.h |  3 +++
 include/linux/skmsg.h  | 35 +++++++++++++++++++++++++++++++++++
 include/net/tcp.h      | 19 -------------------
 net/core/skmsg.c       | 32 ++++++++++++++++++++------------
 net/core/sock_map.c    |  8 ++------
 5 files changed, 60 insertions(+), 37 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6d0a33d1c0db..bd84f799c952 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -755,6 +755,9 @@ struct sk_buff {
 			void		(*destructor)(struct sk_buff *skb);
 		};
 		struct list_head	tcp_tsorted_anchor;
+#ifdef CONFIG_NET_SOCK_MSG
+		unsigned long		_sk_redir;
+#endif
 	};
 
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index e3bb712af257..fc234d507fd7 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -459,4 +459,39 @@ static inline bool sk_psock_strp_enabled(struct sk_psock *psock)
 		return false;
 	return !!psock->saved_data_ready;
 }
+
+#if IS_ENABLED(CONFIG_NET_SOCK_MSG)
+static inline bool skb_bpf_ingress(const struct sk_buff *skb)
+{
+	unsigned long sk_redir = skb->_sk_redir;
+
+	return sk_redir & BPF_F_INGRESS;
+}
+
+static inline void skb_bpf_set_ingress(struct sk_buff *skb)
+{
+	skb->_sk_redir |= BPF_F_INGRESS;
+}
+
+static inline void skb_bpf_set_redir(struct sk_buff *skb, struct sock *sk_redir,
+				     bool ingress)
+{
+	skb->_sk_redir = (unsigned long)sk_redir;
+	if (ingress)
+		skb->_sk_redir |= BPF_F_INGRESS;
+}
+
+static inline struct sock *skb_bpf_redirect_fetch(const struct sk_buff *skb)
+{
+	unsigned long sk_redir = skb->_sk_redir;
+
+	sk_redir &= ~0x1UL;
+	return (struct sock *)sk_redir;
+}
+
+static inline void skb_bpf_redirect_clear(struct sk_buff *skb)
+{
+	skb->_sk_redir = 0;
+}
+#endif /* CONFIG_NET_SOCK_MSG */
 #endif /* _LINUX_SKMSG_H */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 947ef5da6867..075de26f449d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -883,30 +883,11 @@ struct tcp_skb_cb {
 			struct inet6_skb_parm	h6;
 #endif
 		} header;	/* For incoming skbs */
-		struct {
-			__u32 flags;
-			struct sock *sk_redir;
-		} bpf;
 	};
 };
 
 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
 
-static inline bool tcp_skb_bpf_ingress(const struct sk_buff *skb)
-{
-	return TCP_SKB_CB(skb)->bpf.flags & BPF_F_INGRESS;
-}
-
-static inline struct sock *tcp_skb_bpf_redirect_fetch(struct sk_buff *skb)
-{
-	return TCP_SKB_CB(skb)->bpf.sk_redir;
-}
-
-static inline void tcp_skb_bpf_redirect_clear(struct sk_buff *skb)
-{
-	TCP_SKB_CB(skb)->bpf.sk_redir = NULL;
-}
-
 extern const struct inet_connection_sock_af_ops ipv4_specific;
 
 #if IS_ENABLED(CONFIG_IPV6)
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 2d8bbb3fd87c..05b5af09ff42 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -494,6 +494,8 @@ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb
 static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
 			       u32 off, u32 len, bool ingress)
 {
+	skb_bpf_redirect_clear(skb);
+
 	if (!ingress) {
 		if (!sock_writeable(psock->sk))
 			return -EAGAIN;
@@ -525,7 +527,7 @@ static void sk_psock_backlog(struct work_struct *work)
 		len = skb->len;
 		off = 0;
 start:
-		ingress = tcp_skb_bpf_ingress(skb);
+		ingress = skb_bpf_ingress(skb);
 		do {
 			ret = -EIO;
 			if (likely(psock->sk->sk_socket))
@@ -631,7 +633,12 @@ void __sk_psock_purge_ingress_msg(struct sk_psock *psock)
 
 static void sk_psock_zap_ingress(struct sk_psock *psock)
 {
-	__skb_queue_purge(&psock->ingress_skb);
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue(&psock->ingress_skb)) != NULL) {
+		skb_bpf_redirect_clear(skb);
+		kfree_skb(skb);
+	}
 	__sk_psock_purge_ingress_msg(psock);
 }
 
@@ -752,7 +759,7 @@ static void sk_psock_skb_redirect(struct sk_buff *skb)
 	struct sk_psock *psock_other;
 	struct sock *sk_other;
 
-	sk_other = tcp_skb_bpf_redirect_fetch(skb);
+	sk_other = skb_bpf_redirect_fetch(skb);
 	/* This error is a buggy BPF program, it returned a redirect
 	 * return code, but then didn't set a redirect interface.
 	 */
@@ -802,9 +809,10 @@ int sk_psock_tls_strp_read(struct sk_psock *psock, struct sk_buff *skb)
 		 * TLS context.
 		 */
 		skb->sk = psock->sk;
-		tcp_skb_bpf_redirect_clear(skb);
+		skb_dst_drop(skb);
+		skb_bpf_redirect_clear(skb);
 		ret = sk_psock_bpf_run(psock, prog, skb);
-		ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb));
+		ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb));
 		skb->sk = NULL;
 	}
 	sk_psock_tls_verdict_apply(skb, psock->sk, ret);
@@ -816,7 +824,6 @@ EXPORT_SYMBOL_GPL(sk_psock_tls_strp_read);
 static void sk_psock_verdict_apply(struct sk_psock *psock,
 				   struct sk_buff *skb, int verdict)
 {
-	struct tcp_skb_cb *tcp;
 	struct sock *sk_other;
 	int err = -EIO;
 
@@ -828,8 +835,7 @@ static void sk_psock_verdict_apply(struct sk_psock *psock,
 			goto out_free;
 		}
 
-		tcp = TCP_SKB_CB(skb);
-		tcp->bpf.flags |= BPF_F_INGRESS;
+		skb_bpf_set_ingress(skb);
 
 		/* If the queue is empty then we can submit directly
 		 * into the msg queue. If its not empty we have to
@@ -890,9 +896,10 @@ static void sk_psock_strp_read(struct strparser *strp, struct sk_buff *skb)
 	skb_set_owner_r(skb, sk);
 	prog = READ_ONCE(psock->progs.skb_verdict);
 	if (likely(prog)) {
-		tcp_skb_bpf_redirect_clear(skb);
+		skb_dst_drop(skb);
+		skb_bpf_redirect_clear(skb);
 		ret = sk_psock_bpf_run(psock, prog, skb);
-		ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb));
+		ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb));
 	}
 	sk_psock_verdict_apply(psock, skb, ret);
 out:
@@ -1005,9 +1012,10 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb,
 	skb_set_owner_r(skb, sk);
 	prog = READ_ONCE(psock->progs.skb_verdict);
 	if (likely(prog)) {
-		tcp_skb_bpf_redirect_clear(skb);
+		skb_dst_drop(skb);
+		skb_bpf_redirect_clear(skb);
 		ret = sk_psock_bpf_run(psock, prog, skb);
-		ret = sk_psock_map_verd(ret, tcp_skb_bpf_redirect_fetch(skb));
+		ret = sk_psock_map_verd(ret, skb_bpf_redirect_fetch(skb));
 	}
 	sk_psock_verdict_apply(psock, skb, ret);
 out:
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 1a28a5c2c61e..dbfcd7006338 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -657,7 +657,6 @@ const struct bpf_func_proto bpf_sock_map_update_proto = {
 BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb,
 	   struct bpf_map *, map, u32, key, u64, flags)
 {
-	struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
 	struct sock *sk;
 
 	if (unlikely(flags & ~(BPF_F_INGRESS)))
@@ -667,8 +666,7 @@ BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb,
 	if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
 		return SK_DROP;
 
-	tcb->bpf.flags = flags;
-	tcb->bpf.sk_redir = sk;
+	skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
 	return SK_PASS;
 }
 
@@ -1250,7 +1248,6 @@ const struct bpf_func_proto bpf_sock_hash_update_proto = {
 BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb,
 	   struct bpf_map *, map, void *, key, u64, flags)
 {
-	struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
 	struct sock *sk;
 
 	if (unlikely(flags & ~(BPF_F_INGRESS)))
@@ -1260,8 +1257,7 @@ BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb,
 	if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
 		return SK_DROP;
 
-	tcb->bpf.flags = flags;
-	tcb->bpf.sk_redir = sk;
+	skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
 	return SK_PASS;
 }
 
-- 
2.25.1


  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-20  5:29 [Patch bpf-next v6 0/8] sock_map: clean up and refactor code for BPF_SK_SKB_VERDICT Cong Wang
2021-02-20  5:29 ` [Patch bpf-next v6 1/8] bpf: clean up sockmap related Kconfigs Cong Wang
2021-02-22  8:51   ` Jakub Sitnicki
2021-02-22 23:23     ` Cong Wang
2021-02-20  5:29 ` [Patch bpf-next v6 2/8] skmsg: get rid of struct sk_psock_parser Cong Wang
2021-02-20  5:29 ` [Patch bpf-next v6 3/8] bpf: compute data_end dynamically with JIT code Cong Wang
2021-02-20  5:29 ` Cong Wang [this message]
2021-02-22 12:20   ` [Patch bpf-next v6 4/8] skmsg: move sk_redir from TCP_SKB_CB to skb Jakub Sitnicki
2021-02-22 19:27     ` Cong Wang
2021-02-23 17:52       ` Jakub Sitnicki
2021-02-23 18:04         ` Cong Wang
2021-02-23 18:36           ` Jakub Sitnicki
2021-02-20  5:29 ` [Patch bpf-next v6 5/8] sock_map: rename skb_parser and skb_verdict Cong Wang
2021-02-22 12:28   ` Jakub Sitnicki
2021-02-22 19:32     ` Cong Wang
2021-02-20  5:29 ` [Patch bpf-next v6 6/8] sock_map: make sock_map_prog_update() static Cong Wang
2021-02-22 12:29   ` Jakub Sitnicki
2021-02-20  5:29 ` [Patch bpf-next v6 7/8] skmsg: make __sk_psock_purge_ingress_msg() static Cong Wang
2021-02-22 12:30   ` Jakub Sitnicki
2021-02-20  5:29 ` [Patch bpf-next v6 8/8] skmsg: get rid of sk_psock_bpf_run() Cong Wang
2021-02-22 12:31   ` Jakub Sitnicki
2021-02-22 12:32 ` [Patch bpf-next v6 0/8] sock_map: clean up and refactor code for BPF_SK_SKB_VERDICT Jakub Sitnicki

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