Patch "tcp: Introduce tcp_read_skb()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tcp: Introduce tcp_read_skb()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-introduce-tcp_read_skb.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a6e53a6990372e5fcf04b80c77bcf3eb99f7dd5f
Author: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Date:   Wed Jun 15 09:20:11 2022 -0700

    tcp: Introduce tcp_read_skb()
    
    [ Upstream commit 04919bed948dc22a0032a9da867b7dcb8aece4ca ]
    
    This patch inroduces tcp_read_skb() based on tcp_read_sock(),
    a preparation for the next patch which actually introduces
    a new sock ops.
    
    TCP is special here, because it has tcp_read_sock() which is
    mainly used by splice(). tcp_read_sock() supports partial read
    and arbitrary offset, neither of them is needed for sockmap.
    
    Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reviewed-by: John Fastabend <john.fastabend@xxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20220615162014.89193-2-xiyou.wangcong@xxxxxxxxx
    Stable-dep-of: 6648e613226e ("bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 08923ed4278f0..3047a8b3dbd1c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -663,6 +663,8 @@ 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);
 
 void tcp_initialize_rcv_mss(struct sock *sk);
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 16fd3da68e9f6..3647a5f08c22d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1705,6 +1705,53 @@ 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)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 seq = tp->copied_seq;
+	struct sk_buff *skb;
+	int copied = 0;
+	u32 offset;
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -ENOTCONN;
+
+	while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
+		int used;
+
+		__skb_unlink(skb, &sk->sk_receive_queue);
+		used = recv_actor(desc, skb, 0, skb->len);
+		if (used <= 0) {
+			if (!copied)
+				copied = used;
+			break;
+		}
+		seq += used;
+		copied += used;
+
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
+			consume_skb(skb);
+			++seq;
+			break;
+		}
+		consume_skb(skb);
+		if (!desc->count)
+			break;
+		WRITE_ONCE(tp->copied_seq, seq);
+	}
+	WRITE_ONCE(tp->copied_seq, seq);
+
+	tcp_rcv_space_adjust(sk);
+
+	/* Clean up data we have read: This will do ACK frames. */
+	if (copied > 0)
+		tcp_cleanup_rbuf(sk, copied);
+
+	return copied;
+}
+EXPORT_SYMBOL(tcp_read_skb);
+
 int tcp_peek_len(struct socket *sock)
 {
 	return tcp_inq(sock->sk);