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tcp: set TCP_SYNCNT locklessly

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icsk->icsk_syn_retries can safely be set without locking the socket.

We have to add READ_ONCE() annotations in tcp_fastopen_synack_timer()
and tcp_write_timeout().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-08-04 14:46:11 +00:00 committed by David S. Miller
parent 81083076a0
commit d44fd4a767
2 changed files with 12 additions and 12 deletions
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15
net/ipv4/tcp.c
View File

@ -3291,9 +3291,7 @@ int tcp_sock_set_syncnt(struct sock *sk, int val)
if (val < 1 || val > MAX_TCP_SYNCNT)
return -EINVAL;
lock_sock(sk);
WRITE_ONCE(inet_csk(sk)->icsk_syn_retries, val);
release_sock(sk);
return 0;
}
EXPORT_SYMBOL(tcp_sock_set_syncnt);
@ -3462,6 +3460,12 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
if (copy_from_sockptr(&val, optval, sizeof(val)))
return -EFAULT;
/* Handle options that can be set without locking the socket. */
switch (optname) {
case TCP_SYNCNT:
return tcp_sock_set_syncnt(sk, val);
}
sockopt_lock_sock(sk);
switch (optname) {
@ -3569,13 +3573,6 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
else
WRITE_ONCE(tp->keepalive_probes, val);
break;
case TCP_SYNCNT:
if (val < 1 || val > MAX_TCP_SYNCNT)
err = -EINVAL;
else
WRITE_ONCE(icsk->icsk_syn_retries, val);
break;
case TCP_SAVE_SYN:
/* 0: disable, 1: enable, 2: start from ether_header */
if (val < 0 || val > 2)

9
net/ipv4/tcp_timer.c
View File

@ -239,7 +239,8 @@ static int tcp_write_timeout(struct sock *sk)
if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
if (icsk->icsk_retransmits)
__dst_negative_advice(sk);
retry_until = icsk->icsk_syn_retries ? :
/* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */
retry_until = READ_ONCE(icsk->icsk_syn_retries) ? :
READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
max_retransmits = retry_until;
@ -421,8 +422,10 @@ static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
req->rsk_ops->syn_ack_timeout(req);
/* add one more retry for fastopen */
max_retries = icsk->icsk_syn_retries ? :
/* Add one more retry for fastopen.
* Paired with WRITE_ONCE() in tcp_sock_set_syncnt()
*/
max_retries = READ_ONCE(icsk->icsk_syn_retries) ? :
READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1;
if (req->num_timeout >= max_retries) {