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tcp: Split out __tcp_set_rcvlowat().

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We will add a kfunc for bpf_tcp_ops.{enqueue,dequeue}_rcvq()
to adjust sk->sk_rcvlowat.

These hooks are triggered

  * when the TCP stack enqueues an skb to sk->sk_receive_queue
  * after data is dequeued from sk->sk_receive_queue

In the enqueue path, tcp_data_ready() is always called after
the hooks in tcp_queue_rcv() and tcp_ofo_queue().

If tcp_set_rcvlowat() were used as is, tcp_data_ready() could
be called twice for the same skb, which is redundant and also
confusing.

Let's split out __tcp_set_rcvlowat() and add a flag to control
wakeup behaviour.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20261008031604.256498-8-kuniyu@google.com
This commit is contained in:
Kuniyuki Iwashima 2026-10-08 03:15:27 +00:00 committed by Alexei Starovoitov
parent 32d17fe8a9
commit dcddae18f5
No known key found for this signature in database
2 changed files with 10 additions and 3 deletions
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1
include/net/tcp.h
View File

@ -512,6 +512,7 @@ void tcp_set_keepalive(struct sock *sk, int val);
void tcp_syn_ack_timeout(const struct request_sock *req);
int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
int flags);
int __tcp_set_rcvlowat(struct sock *sk, int val, bool wakeup);
int tcp_set_rcvlowat(struct sock *sk, int val);
void tcp_set_rcvbuf(struct sock *sk, int val);
int tcp_set_window_clamp(struct sock *sk, int val);

12
net/ipv4/tcp.c
View File

@ -1827,8 +1827,7 @@ int tcp_peek_len(struct socket *sock)
return tcp_inq(sock->sk);
}
/* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */
int tcp_set_rcvlowat(struct sock *sk, int val)
int __tcp_set_rcvlowat(struct sock *sk, int val, bool wakeup)
{
struct tcp_sock *tp = tcp_sk(sk);
int space, cap;
@ -1841,7 +1840,8 @@ int tcp_set_rcvlowat(struct sock *sk, int val)
WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
/* Check if we need to signal EPOLLIN right now */
tcp_data_ready(sk);
if (wakeup)
tcp_data_ready(sk);
if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
return 0;
@ -1856,6 +1856,12 @@ int tcp_set_rcvlowat(struct sock *sk, int val)
return 0;
}
/* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */
int tcp_set_rcvlowat(struct sock *sk, int val)
{
return __tcp_set_rcvlowat(sk, val, true);
}
void tcp_set_rcvbuf(struct sock *sk, int val)
{
tcp_set_window_clamp(sk, tcp_win_from_space(sk, val));