[PATCH net-next v4 0/2] support TCP_RTO_MIN_US and TCP_DELACK_MAX_US for set/getsockopt

[PATCH net-next v4 0/2] support TCP_RTO_MIN_US and TCP_DELACK_MAX_US for set/getsockopt

[Jason Xing]

Add set/getsockopt supports for TCP_RTO_MIN_US and TCP_DELACK_MAX_US.

v4
1. add more detailed information into commit log (Eric)
2. use val directly in do_tcp_getsockopt (Eric)

Jason Xing (2):
  tcp: support TCP_RTO_MIN_US for set/getsockopt use
  tcp: support TCP_DELACK_MAX_US for set/getsockopt use

 Documentation/networking/ip-sysctl.rst |  4 ++--
 include/net/tcp.h                      |  2 +-
 include/uapi/linux/tcp.h               |  2 ++
 net/ipv4/tcp.c                         | 26 ++++++++++++++++++++++++--
 net/ipv4/tcp_output.c                  |  2 +-
 5 files changed, 30 insertions(+), 6 deletions(-)

-- 
2.43.5

[PATCH net-next v4 1/2] tcp: support TCP_RTO_MIN_US for set/getsockopt use

[Jason Xing]

Support adjusting/reading RTO MIN for socket level by using set/getsockopt().

This new option has the same effect as TCP_BPF_RTO_MIN, which means it
doesn't affect RTAX_RTO_MIN usage (by using ip route...). Considering that
bpf option was implemented before this patch, so we need to use a standalone
new option for pure tcp set/getsockopt() use.

When the socket is created, its icsk_rto_min is set to the default
value that is controlled by sysctl_tcp_rto_min_us. Then if application
calls setsockopt() with TCP_RTO_MIN_US flag to pass a valid value, then
icsk_rto_min will be overridden in jiffies unit.

This patch adds WRITE_ONCE/READ_ONCE to avoid data-race around
icsk_rto_min.

Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
---
 Documentation/networking/ip-sysctl.rst |  4 ++--
 include/net/tcp.h                      |  2 +-
 include/uapi/linux/tcp.h               |  1 +
 net/ipv4/tcp.c                         | 13 ++++++++++++-
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 054561f8dcae..5c63ab928b97 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1229,8 +1229,8 @@ tcp_pingpong_thresh - INTEGER
 tcp_rto_min_us - INTEGER
 	Minimal TCP retransmission timeout (in microseconds). Note that the
 	rto_min route option has the highest precedence for configuring this
-	setting, followed by the TCP_BPF_RTO_MIN socket option, followed by
-	this tcp_rto_min_us sysctl.
+	setting, followed by the TCP_BPF_RTO_MIN and TCP_RTO_MIN_US socket
+	options, followed by this tcp_rto_min_us sysctl.
 
 	The recommended practice is to use a value less or equal to 200000
 	microseconds.
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7207c52b1fc9..6a7aab854b86 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -806,7 +806,7 @@ u32 tcp_delack_max(const struct sock *sk);
 static inline u32 tcp_rto_min(const struct sock *sk)
 {
 	const struct dst_entry *dst = __sk_dst_get(sk);
-	u32 rto_min = inet_csk(sk)->icsk_rto_min;
+	u32 rto_min = READ_ONCE(inet_csk(sk)->icsk_rto_min);
 
 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 32a27b4a5020..b2476cf7058e 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -137,6 +137,7 @@ 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_REPAIR_ON		1
 #define TCP_REPAIR_OFF		0
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 46951e749308..b89c1b676b8e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3352,7 +3352,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	icsk->icsk_probes_out = 0;
 	icsk->icsk_probes_tstamp = 0;
 	icsk->icsk_rto = TCP_TIMEOUT_INIT;
-	icsk->icsk_rto_min = TCP_RTO_MIN;
+	WRITE_ONCE(icsk->icsk_rto_min, TCP_RTO_MIN);
 	icsk->icsk_delack_max = TCP_DELACK_MAX;
 	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 	tcp_snd_cwnd_set(tp, TCP_INIT_CWND);
@@ -3833,6 +3833,14 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 			return -EINVAL;
 		WRITE_ONCE(inet_csk(sk)->icsk_rto_max, msecs_to_jiffies(val));
 		return 0;
+	case TCP_RTO_MIN_US: {
+		int rto_min = usecs_to_jiffies(val);
+
+		if (rto_min > TCP_RTO_MIN || rto_min < TCP_TIMEOUT_MIN)
+			return -EINVAL;
+		WRITE_ONCE(inet_csk(sk)->icsk_rto_min, rto_min);
+		return 0;
+	}
 	}
 
 	sockopt_lock_sock(sk);
@@ -4672,6 +4680,9 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 	case TCP_RTO_MAX_MS:
 		val = jiffies_to_msecs(tcp_rto_max(sk));
 		break;
+	case TCP_RTO_MIN_US:
+		val = jiffies_to_usecs(READ_ONCE(inet_csk(sk)->icsk_rto_min));
+		break;
 	default:
 		return -ENOPROTOOPT;
 	}
-- 
2.43.5

Re: [PATCH net-next v4 1/2] tcp: support TCP_RTO_MIN_US for set/getsockopt use

[Eric Dumazet]

On Mon, Mar 17, 2025 at 1:03 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> Support adjusting/reading RTO MIN for socket level by using set/getsockopt().
>
> This new option has the same effect as TCP_BPF_RTO_MIN, which means it
> doesn't affect RTAX_RTO_MIN usage (by using ip route...). Considering that
> bpf option was implemented before this patch, so we need to use a standalone
> new option for pure tcp set/getsockopt() use.
>
> When the socket is created, its icsk_rto_min is set to the default
> value that is controlled by sysctl_tcp_rto_min_us. Then if application
> calls setsockopt() with TCP_RTO_MIN_US flag to pass a valid value, then
> icsk_rto_min will be overridden in jiffies unit.
>
> This patch adds WRITE_ONCE/READ_ONCE to avoid data-race around
> icsk_rto_min.
>
> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
> ---
>  Documentation/networking/ip-sysctl.rst |  4 ++--
>  include/net/tcp.h                      |  2 +-
>  include/uapi/linux/tcp.h               |  1 +
>  net/ipv4/tcp.c                         | 13 ++++++++++++-
>  4 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index 054561f8dcae..5c63ab928b97 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -1229,8 +1229,8 @@ tcp_pingpong_thresh - INTEGER
>  tcp_rto_min_us - INTEGER
>         Minimal TCP retransmission timeout (in microseconds). Note that the
>         rto_min route option has the highest precedence for configuring this
> -       setting, followed by the TCP_BPF_RTO_MIN socket option, followed by
> -       this tcp_rto_min_us sysctl.
> +       setting, followed by the TCP_BPF_RTO_MIN and TCP_RTO_MIN_US socket
> +       options, followed by this tcp_rto_min_us sysctl.
>
>         The recommended practice is to use a value less or equal to 200000
>         microseconds.
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 7207c52b1fc9..6a7aab854b86 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -806,7 +806,7 @@ u32 tcp_delack_max(const struct sock *sk);
>  static inline u32 tcp_rto_min(const struct sock *sk)
>  {
>         const struct dst_entry *dst = __sk_dst_get(sk);
> -       u32 rto_min = inet_csk(sk)->icsk_rto_min;
> +       u32 rto_min = READ_ONCE(inet_csk(sk)->icsk_rto_min);
>
>         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
>                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index 32a27b4a5020..b2476cf7058e 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -137,6 +137,7 @@ 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_REPAIR_ON          1
>  #define TCP_REPAIR_OFF         0
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 46951e749308..b89c1b676b8e 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3352,7 +3352,7 @@ int tcp_disconnect(struct sock *sk, int flags)
>         icsk->icsk_probes_out = 0;
>         icsk->icsk_probes_tstamp = 0;
>         icsk->icsk_rto = TCP_TIMEOUT_INIT;
> -       icsk->icsk_rto_min = TCP_RTO_MIN;
> +       WRITE_ONCE(icsk->icsk_rto_min, TCP_RTO_MIN);

Semi-orthogonal to your patch, apparently at disconnect() we throw
away user/eBPF choice.

Most socket options, once set via setsockopt() should stay even if the
socket is re-used.

Reviewed-by: Eric Dumazet <edumazet@google.com>

[PATCH net-next v4 2/2] tcp: support TCP_DELACK_MAX_US for set/getsockopt use

[Jason Xing]

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>
---
 include/uapi/linux/tcp.h |  1 +
 net/ipv4/tcp.c           | 13 ++++++++++++-
 net/ipv4/tcp_output.c    |  2 +-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index b2476cf7058e..2377e22f2c4b 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -138,6 +138,7 @@ 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
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b89c1b676b8e..578e79024955 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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;
 	}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 24e56bf96747..65aa26d65987 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -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
-- 
2.43.5

Re: [PATCH net-next v4 2/2] tcp: support TCP_DELACK_MAX_US for set/getsockopt use

[Eric Dumazet]

On Mon, Mar 17, 2025 at 1:03 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> 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>
> ---
>  include/uapi/linux/tcp.h |  1 +
>  net/ipv4/tcp.c           | 13 ++++++++++++-
>  net/ipv4/tcp_output.c    |  2 +-
>  3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index b2476cf7058e..2377e22f2c4b 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -138,6 +138,7 @@ 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
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index b89c1b676b8e..578e79024955 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -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);

Same comment here as the first patch, I think we should not change
csk->icsk_delack_max in tcp_disconnect(),
otherwise a prior setsockopt() setting is erased.

Probably not a big deal, and if it is, could be fixed in a followup patch.

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net-next v4 2/2] tcp: support TCP_DELACK_MAX_US for set/getsockopt use

[Jason Xing]

On Tue, Mar 25, 2025 at 7:13 PM Eric Dumazet <edumazet@google.com> wrote:
>
> On Mon, Mar 17, 2025 at 1:03 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
> >
> > 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>
> > ---
> >  include/uapi/linux/tcp.h |  1 +
> >  net/ipv4/tcp.c           | 13 ++++++++++++-
> >  net/ipv4/tcp_output.c    |  2 +-
> >  3 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> > index b2476cf7058e..2377e22f2c4b 100644
> > --- a/include/uapi/linux/tcp.h
> > +++ b/include/uapi/linux/tcp.h
> > @@ -138,6 +138,7 @@ 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
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index b89c1b676b8e..578e79024955 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -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);
>
> Same comment here as the first patch, I think we should not change
> csk->icsk_delack_max in tcp_disconnect(),
> otherwise a prior setsockopt() setting is erased.
>
> Probably not a big deal, and if it is, could be fixed in a followup patch.

Got it. Thanks.

Thanks,
Jason

>
> Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net-next v4 0/2] support TCP_RTO_MIN_US and TCP_DELACK_MAX_US for set/getsockopt

[Jason Xing]

On Mon, Mar 17, 2025 at 8:03 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> Add set/getsockopt supports for TCP_RTO_MIN_US and TCP_DELACK_MAX_US.
>
> v4
> 1. add more detailed information into commit log (Eric)
> 2. use val directly in do_tcp_getsockopt (Eric)
>
> Jason Xing (2):
>   tcp: support TCP_RTO_MIN_US for set/getsockopt use
>   tcp: support TCP_DELACK_MAX_US for set/getsockopt use

Gentle ping here :) I noticed that net-next is closed, so I decided to
reply to this thread.

Thanks,
Jason

>
>  Documentation/networking/ip-sysctl.rst |  4 ++--
>  include/net/tcp.h                      |  2 +-
>  include/uapi/linux/tcp.h               |  2 ++
>  net/ipv4/tcp.c                         | 26 ++++++++++++++++++++++++--
>  net/ipv4/tcp_output.c                  |  2 +-
>  5 files changed, 30 insertions(+), 6 deletions(-)
>
> --
> 2.43.5
>

Re: [PATCH net-next v4 0/2] support TCP_RTO_MIN_US and TCP_DELACK_MAX_US for set/getsockopt

[Jason Xing]

On Tue, Mar 25, 2025 at 12:35 AM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> On Mon, Mar 17, 2025 at 8:03 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
> >
> > Add set/getsockopt supports for TCP_RTO_MIN_US and TCP_DELACK_MAX_US.
> >
> > v4
> > 1. add more detailed information into commit log (Eric)
> > 2. use val directly in do_tcp_getsockopt (Eric)
> >
> > Jason Xing (2):
> >   tcp: support TCP_RTO_MIN_US for set/getsockopt use
> >   tcp: support TCP_DELACK_MAX_US for set/getsockopt use
>
> Gentle ping here :) I noticed that net-next is closed, so I decided to
> reply to this thread.

Oh, I should have noticed that most of the core maintainers are absent
these days. Sorry, I don't expect to add more burden so I can resend
after net-next is open. Anyway, either way is fine with me. Just
please let me know :)

Thank you.

>
> Thanks,
> Jason
>
> >
> >  Documentation/networking/ip-sysctl.rst |  4 ++--
> >  include/net/tcp.h                      |  2 +-
> >  include/uapi/linux/tcp.h               |  2 ++
> >  net/ipv4/tcp.c                         | 26 ++++++++++++++++++++++++--
> >  net/ipv4/tcp_output.c                  |  2 +-
> >  5 files changed, 30 insertions(+), 6 deletions(-)
> >
> > --
> > 2.43.5
> >

Re: [PATCH net-next v4 0/2] support TCP_RTO_MIN_US and TCP_DELACK_MAX_US for set/getsockopt

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 17 Mar 2025 20:03:12 +0800 you wrote:
> Add set/getsockopt supports for TCP_RTO_MIN_US and TCP_DELACK_MAX_US.
> 
> v4
> 1. add more detailed information into commit log (Eric)
> 2. use val directly in do_tcp_getsockopt (Eric)
> 
> Jason Xing (2):
>   tcp: support TCP_RTO_MIN_US for set/getsockopt use
>   tcp: support TCP_DELACK_MAX_US for set/getsockopt use
> 
> [...]

Here is the summary with links:
  - [net-next,v4,1/2] tcp: support TCP_RTO_MIN_US for set/getsockopt use
    https://git.kernel.org/netdev/net-next/c/f38805c5d26f
  - [net-next,v4,2/2] tcp: support TCP_DELACK_MAX_US for set/getsockopt use
    https://git.kernel.org/netdev/net-next/c/9552f90835ef

You are awesome, thank you!
-- 
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