Cong Wang wrote:
> From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
>
> 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.
>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
> Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> ---
> include/net/tcp.h | 2 ++
> net/ipv4/tcp.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 49 insertions(+)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 1e99f5c61f84..878544d0f8f9 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -669,6 +669,8 @@ 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 9984d23a7f3e..a18e9ababf54 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1709,6 +1709,53 @@ 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) {
> + kfree_skb(skb);
Hi Cong, can you elaborate here from v2 comment.
"Hm, it is tricky here, we use the skb refcount after this patchset, so
it could be a real drop from another kfree_skb() in net/core/skmsg.c
which initiates the drop."
The tcp_read_sock() hook is using tcp_eat_recv_skb(). Are we going
to kick tracing infra even on good cases with kfree_skb()? In
sk_psock_verdict_recv() we do an skb_clone() there.
.John
