Commit db4192a7 authored by Cong Wang's avatar Cong Wang Committed by Paolo Abeni
Browse files

tcp: read multiple skbs in tcp_read_skb() 



Before we switched to ->read_skb(), ->read_sock() was passed with
desc.count=1, which technically indicates we only read one skb per
->sk_data_ready() call. However, for TCP, this is not true.

TCP at least has sk_rcvlowat which intentionally holds skb's in
receive queue until this watermark is reached. This means when
->sk_data_ready() is invoked there could be multiple skb's in the
queue, therefore we have to read multiple skbs in tcp_read_skb()
instead of one.

Fixes: 965b57b4 ("net: Introduce a new proto_ops ->read_skb()")
Reported-by: default avatarPeilin Ye <peilin.ye@bytedance.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: default avatarCong Wang <cong.wang@bytedance.com>
Link: https://lore.kernel.org/r/20220912173553.235838-1-xiyou.wangcong@gmail.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 90fdd1c1

net/ipv4/tcp.c

+19 −10
Original line number Diff line number Diff line
@@ -1761,19 +1761,28 @@ int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor) 
	if (sk->sk_state == TCP_LISTEN)

		return -ENOTCONN;



	skb = tcp_recv_skb(sk, seq, &offset);

	if (!skb)

		return 0;

	while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {

		u8 tcp_flags;

		int used;



		__skb_unlink(skb, &sk->sk_receive_queue);

		WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk));

	copied = recv_actor(sk, skb);

	if (copied >= 0) {

		seq += copied;

		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)

		tcp_flags = TCP_SKB_CB(skb)->tcp_flags;

		used = recv_actor(sk, skb);

		consume_skb(skb);

		if (used < 0) {

			if (!copied)

				copied = used;

			break;

		}

		seq += used;

		copied += used;



		if (tcp_flags & TCPHDR_FIN) {

			++seq;

			break;

		}

	}

	consume_skb(skb);

	WRITE_ONCE(tp->copied_seq, seq);



	tcp_rcv_space_adjust(sk);