Commit 9552f908 authored by Jason Xing's avatar Jason Xing Committed by Jakub Kicinski
Browse files

tcp: support TCP_DELACK_MAX_US for set/getsockopt use 



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: default avatarJason Xing <kerneljasonxing@gmail.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250317120314.41404-3-kerneljasonxing@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent f38805c5

include/uapi/linux/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -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

net/ipv4/tcp.c

+12 −1
Original line number Diff line number Diff line
@@ -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;

	}

net/ipv4/tcp_output.c

+1 −1
Original line number Diff line number Diff line
@@ -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