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tcp: support TCP_DELACK_MAX_US for set/getsockopt use

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Support adjusting/reading delayed ack max for socket level by using
set/getsockopt().

This option aligns with TCP_BPF_DELACK_MAX usage. Considering that bpf
option was implemented before this patch, so we need to use a standalone
new option for pure tcp set/getsockopt() use.

Add WRITE_ONCE/READ_ONCE() to prevent data-race if setsockopt()
happens to write one value to icsk_delack_max while icsk_delack_max is
being read.

Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250317120314.41404-3-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jason Xing 2025-03-17 20:03:14 +08:00 committed by Jakub Kicinski
parent f38805c5d2
commit 9552f90835
3 changed files with 14 additions and 2 deletions
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1
include/uapi/linux/tcp.h
View File

@ -141,6 +141,7 @@ enum {
#define TCP_IS_MPTCP 43 /* Is MPTCP being used? */
#define TCP_RTO_MAX_MS 44 /* max rto time in ms */
#define TCP_RTO_MIN_US 45 /* min rto time in us */
#define TCP_DELACK_MAX_US 46 /* max delayed ack time in us */
#define TCP_REPAIR_ON 1
#define TCP_REPAIR_OFF 0

13
net/ipv4/tcp.c
View File

@ -3353,7 +3353,7 @@ int tcp_disconnect(struct sock *sk, int flags)
icsk->icsk_probes_tstamp = 0;
icsk->icsk_rto = TCP_TIMEOUT_INIT;
WRITE_ONCE(icsk->icsk_rto_min, TCP_RTO_MIN);
icsk->icsk_delack_max = TCP_DELACK_MAX;
WRITE_ONCE(icsk->icsk_delack_max, TCP_DELACK_MAX);
tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
tcp_snd_cwnd_set(tp, TCP_INIT_CWND);
tp->snd_cwnd_cnt = 0;
@ -3841,6 +3841,14 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
WRITE_ONCE(inet_csk(sk)->icsk_rto_min, rto_min);
return 0;
}
case TCP_DELACK_MAX_US: {
int delack_max = usecs_to_jiffies(val);
if (delack_max > TCP_DELACK_MAX || delack_max < TCP_TIMEOUT_MIN)
return -EINVAL;
WRITE_ONCE(inet_csk(sk)->icsk_delack_max, delack_max);
return 0;
}
}
sockopt_lock_sock(sk);
@ -4683,6 +4691,9 @@ int do_tcp_getsockopt(struct sock *sk, int level,
case TCP_RTO_MIN_US:
val = jiffies_to_usecs(READ_ONCE(inet_csk(sk)->icsk_rto_min));
break;
case TCP_DELACK_MAX_US:
val = jiffies_to_usecs(READ_ONCE(inet_csk(sk)->icsk_delack_max));
break;
default:
return -ENOPROTOOPT;
}

2
net/ipv4/tcp_output.c
View File

@ -4179,7 +4179,7 @@ u32 tcp_delack_max(const struct sock *sk)
{
u32 delack_from_rto_min = max(tcp_rto_min(sk), 2) - 1;
return min(inet_csk(sk)->icsk_delack_max, delack_from_rto_min);
return min(READ_ONCE(inet_csk(sk)->icsk_delack_max), delack_from_rto_min);
}
/* Send out a delayed ack, the caller does the policy checking