net: Introduce a new proto_ops ->read_skb()

Currently both splice() and sockmap use ->read_sock() to
read skb from receive queue, but for sockmap we only read
one entire skb at a time, so ->read_sock() is too conservative
to use. Introduce a new proto_ops ->read_skb() which supports
this sematic, with this we can finally pass the ownership of
skb to recv actors.

For non-TCP protocols, all ->read_sock() can be simply
converted to ->read_skb().
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20220615162014.89193-3-xiyou.wangcong@gmail.com

include/linux/net.h

@@ -152,6 +152,8 @@ struct module;
 struct sk_buff;
 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
 			       unsigned int, size_t);
+typedef int (*skb_read_actor_t)(struct sock *, struct sk_buff *);
+
 
 struct proto_ops {
 	int		family;
@@ -214,6 +216,8 @@ struct proto_ops {
 	 */
 	int		(*read_sock)(struct sock *sk, read_descriptor_t *desc,
 				     sk_read_actor_t recv_actor);
+	/* This is different from read_sock(), it reads an entire skb at a time. */
+	int		(*read_skb)(struct sock *sk, skb_read_actor_t recv_actor);
 	int		(*sendpage_locked)(struct sock *sk, struct page *page,
 					   int offset, size_t size, int flags);
 	int		(*sendmsg_locked)(struct sock *sk, struct msghdr *msg,

include/net/tcp.h

@@ -672,8 +672,7 @@ void tcp_get_info(struct sock *, struct tcp_info *);
 /* Read 'sendfile()'-style from a TCP socket */
 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 		  sk_read_actor_t recv_actor);
-int tcp_read_skb(struct sock *sk, read_descriptor_t *desc,
-		 sk_read_actor_t recv_actor);
+int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
 
 void tcp_initialize_rcv_mss(struct sock *sk);
 

include/net/udp.h

@@ -306,8 +306,7 @@ struct sock *__udp6_lib_lookup(struct net *net,
 			       struct sk_buff *skb);
 struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
-int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
-		  sk_read_actor_t recv_actor);
+int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
 
 /* UDP uses skb->dev_scratch to cache as much information as possible and avoid
  * possibly multiple cache miss on dequeue()

net/core/skmsg.c

@@ -1160,21 +1160,17 @@ static void sk_psock_done_strp(struct sk_psock *psock)
 }
 #endif /* CONFIG_BPF_STREAM_PARSER */
 
-static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb,
-				 unsigned int offset, size_t orig_len)
+static int sk_psock_verdict_recv(struct sock *sk, struct sk_buff *skb)
 {
-	struct sock *sk = (struct sock *)desc->arg.data;
 	struct sk_psock *psock;
 	struct bpf_prog *prog;
 	int ret = __SK_DROP;
-	int len = orig_len;
+	int len = skb->len;
 
 	/* clone here so sk_eat_skb() in tcp_read_sock does not drop our data */
 	skb = skb_clone(skb, GFP_ATOMIC);
-	if (!skb) {
-		desc->error = -ENOMEM;
+	if (!skb)
 		return 0;
-	}
 
 	rcu_read_lock();
 	psock = sk_psock(sk);
@@ -1204,16 +1200,10 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb,
 static void sk_psock_verdict_data_ready(struct sock *sk)
 {
 	struct socket *sock = sk->sk_socket;
-	read_descriptor_t desc;
 
-	if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
+	if (unlikely(!sock || !sock->ops || !sock->ops->read_skb))
 		return;
-
-	desc.arg.data = sk;
-	desc.error = 0;
-	desc.count = 1;
-
-	sock->ops->read_sock(sk, &desc, sk_psock_verdict_recv);
+	sock->ops->read_skb(sk, sk_psock_verdict_recv);
 }
 
 void sk_psock_start_verdict(struct sock *sk, struct sk_psock *psock)

net/ipv4/af_inet.c

@@ -1040,6 +1040,7 @@ const struct proto_ops inet_stream_ops = {
 	.sendpage	   = inet_sendpage,
 	.splice_read	   = tcp_splice_read,
 	.read_sock	   = tcp_read_sock,
+	.read_skb	   = tcp_read_skb,
 	.sendmsg_locked    = tcp_sendmsg_locked,
 	.sendpage_locked   = tcp_sendpage_locked,
 	.peek_len	   = tcp_peek_len,
@@ -1067,7 +1068,7 @@ const struct proto_ops inet_dgram_ops = {
 	.setsockopt	   = sock_common_setsockopt,
 	.getsockopt	   = sock_common_getsockopt,
 	.sendmsg	   = inet_sendmsg,
-	.read_sock	   = udp_read_sock,
+	.read_skb	   = udp_read_skb,
 	.recvmsg	   = inet_recvmsg,
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = inet_sendpage,

net/ipv4/tcp.c

@@ -1734,8 +1734,7 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 }
 EXPORT_SYMBOL(tcp_read_sock);
 
-int tcp_read_skb(struct sock *sk, read_descriptor_t *desc,
-		 sk_read_actor_t recv_actor)
+int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 seq = tp->copied_seq;
@@ -1750,7 +1749,7 @@ int tcp_read_skb(struct sock *sk, read_descriptor_t *desc,
 		int used;
 
 		__skb_unlink(skb, &sk->sk_receive_queue);
-		used = recv_actor(desc, skb, 0, skb->len);
+		used = recv_actor(sk, skb);
 		if (used <= 0) {
 			if (!copied)
 				copied = used;
@@ -1765,9 +1764,7 @@ int tcp_read_skb(struct sock *sk, read_descriptor_t *desc,
 			break;
 		}
 		consume_skb(skb);
-		if (!desc->count)
-			break;
-		WRITE_ONCE(tp->copied_seq, seq);
+		break;
 	}
 	WRITE_ONCE(tp->copied_seq, seq);
 

net/ipv4/udp.c

@@ -1797,8 +1797,7 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
 }
 EXPORT_SYMBOL(__skb_recv_udp);
 
-int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
-		  sk_read_actor_t recv_actor)
+int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
 	int copied = 0;
 
@@ -1820,7 +1819,7 @@ int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
 			continue;
 		}
 
-		used = recv_actor(desc, skb, 0, skb->len);
+		used = recv_actor(sk, skb);
 		if (used <= 0) {
 			if (!copied)
 				copied = used;
@@ -1831,13 +1830,12 @@ int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
 		}
 
 		kfree_skb(skb);
-		if (!desc->count)
-			break;
+		break;
 	}
 
 	return copied;
 }
-EXPORT_SYMBOL(udp_read_sock);
+EXPORT_SYMBOL(udp_read_skb);
 
 /*
  * 	This should be easy, if there is something there we

net/ipv6/af_inet6.c

@@ -702,6 +702,7 @@ const struct proto_ops inet6_stream_ops = {
 	.sendpage_locked   = tcp_sendpage_locked,
 	.splice_read	   = tcp_splice_read,
 	.read_sock	   = tcp_read_sock,
+	.read_skb	   = tcp_read_skb,
 	.peek_len	   = tcp_peek_len,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	   = inet6_compat_ioctl,
@@ -727,7 +728,7 @@ const struct proto_ops inet6_dgram_ops = {
 	.getsockopt	   = sock_common_getsockopt,	/* ok		*/
 	.sendmsg	   = inet6_sendmsg,		/* retpoline's sake */
 	.recvmsg	   = inet6_recvmsg,		/* retpoline's sake */
-	.read_sock	   = udp_read_sock,
+	.read_skb	   = udp_read_skb,
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = sock_no_sendpage,
 	.set_peek_off	   = sk_set_peek_off,

net/unix/af_unix.c

@@ -741,10 +741,8 @@ static ssize_t unix_stream_splice_read(struct socket *,  loff_t *ppos,
 				       unsigned int flags);
 static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);
 static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);
-static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
-			  sk_read_actor_t recv_actor);
-static int unix_stream_read_sock(struct sock *sk, read_descriptor_t *desc,
-				 sk_read_actor_t recv_actor);
+static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
+static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
 static int unix_dgram_connect(struct socket *, struct sockaddr *,
 			      int, int);
 static int unix_seqpacket_sendmsg(struct socket *, struct msghdr *, size_t);
@@ -798,7 +796,7 @@ static const struct proto_ops unix_stream_ops = {
 	.shutdown =	unix_shutdown,
 	.sendmsg =	unix_stream_sendmsg,
 	.recvmsg =	unix_stream_recvmsg,
-	.read_sock =	unix_stream_read_sock,
+	.read_skb =	unix_stream_read_skb,
 	.mmap =		sock_no_mmap,
 	.sendpage =	unix_stream_sendpage,
 	.splice_read =	unix_stream_splice_read,
@@ -823,7 +821,7 @@ static const struct proto_ops unix_dgram_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	unix_shutdown,
 	.sendmsg =	unix_dgram_sendmsg,
-	.read_sock =	unix_read_sock,
+	.read_skb =	unix_read_skb,
 	.recvmsg =	unix_dgram_recvmsg,
 	.mmap =		sock_no_mmap,
 	.sendpage =	sock_no_sendpage,
@@ -2487,8 +2485,7 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg, size_t si
 	return __unix_dgram_recvmsg(sk, msg, size, flags);
 }
 
-static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
-			  sk_read_actor_t recv_actor)
+static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
 	int copied = 0;
 
@@ -2503,7 +2500,7 @@ static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
 		if (!skb)
 			return err;
 
-		used = recv_actor(desc, skb, 0, skb->len);
+		used = recv_actor(sk, skb);
 		if (used <= 0) {
 			if (!copied)
 				copied = used;
@@ -2514,8 +2511,7 @@ static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
 		}
 
 		kfree_skb(skb);
-		if (!desc->count)
-			break;
+		break;
 	}
 
 	return copied;
@@ -2650,13 +2646,12 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
 }
 #endif
 
-static int unix_stream_read_sock(struct sock *sk, read_descriptor_t *desc,
-				 sk_read_actor_t recv_actor)
+static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
 	if (unlikely(sk->sk_state != TCP_ESTABLISHED))
 		return -ENOTCONN;
 
-	return unix_read_sock(sk, desc, recv_actor);
+	return unix_read_skb(sk, recv_actor);
 }
 
 static int unix_stream_read_generic(struct unix_stream_read_state *state,