[PATCH v2 net-next] inet_diag: report delayed ack timer information

[PATCH v2 net-next] inet_diag: report delayed ack timer information

[Eric Dumazet]

inet_sk_diag_fill() populates r->idiag_timer with the following
precedence order:

1 - Retransmit timer.
4 - Probe0 timer.
2 - Keepalive timer.

This patch adds a new value, last in the list, if other timers
are not active.

5 - Delayed ACK timer.

A corresponding iproute2 patch will follow to replace "unknown"
with "delack":

ESTAB 10     0   [2002:a05:6830:1f86::]:12875 [2002:a05:6830:1f85::]:50438

    timer:(unknown,003ms,0) ino:152178 sk:3004 cgroup:unreachable:189 <->

    skmem:(r1344,rb12780520,t0,tb262144,f2752,w0,o250,bl0,d0) ts usec_ts
    ...

Also add the following enum in uapi/linux/inet_diag.h
as suggested by David Ahern.

enum {
	IDIAG_TIMER_OFF,
	IDIAG_TIMER_ON,
	IDIAG_TIMER_KEEPALIVE,
	IDIAG_TIMER_TIMEWAIT,
	IDIAG_TIMER_PROBE0,
	IDIAG_TIMER_DELACK,
};

Neal Cardwell suggested to test for ICSK_ACK_TIMER:
inet_csk_clear_xmit_timer() does not call sk_stop_timer()
because INET_CSK_CLEAR_TIMERS is unset.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
---
 include/uapi/linux/inet_diag.h |  9 +++++++++
 net/ipv4/inet_diag.c           | 13 +++++++++----
 net/ipv4/tcp_diag.c            |  4 ++--
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h
index 86bb2e8b17c9f197fd49cf7996d5e4f555a9b8e8..21f0d735fbae206cf2e1e573912a324bb2eb64d9 100644
--- a/include/uapi/linux/inet_diag.h
+++ b/include/uapi/linux/inet_diag.h
@@ -129,6 +129,15 @@ struct inet_diag_msg {
 	__u32	idiag_inode;
 };
 
+enum {
+	IDIAG_TIMER_OFF,
+	IDIAG_TIMER_ON,
+	IDIAG_TIMER_KEEPALIVE,
+	IDIAG_TIMER_TIMEWAIT,
+	IDIAG_TIMER_PROBE0,
+	IDIAG_TIMER_DELACK,
+};
+
 /* Extensions */
 
 enum {
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 9d215485b5c7e7ba29dd53c924f0245439d74af5..34b77aa87d0a48bcbceb7f2935a210a347812cc6 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -241,7 +241,7 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
 
 	inet_diag_msg_common_fill(r, sk);
 	r->idiag_state = sk->sk_state;
-	r->idiag_timer = 0;
+	r->idiag_timer = IDIAG_TIMER_OFF;
 	r->idiag_retrans = 0;
 	r->idiag_expires = 0;
 
@@ -284,20 +284,25 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
 	if (icsk_pending == ICSK_TIME_RETRANS ||
 	    icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 	    icsk_pending == ICSK_TIME_LOSS_PROBE) {
-		r->idiag_timer = 1;
+		r->idiag_timer = IDIAG_TIMER_ON;
 		r->idiag_retrans = READ_ONCE(icsk->icsk_retransmits);
 		r->idiag_expires =
 			jiffies_delta_to_msecs(tcp_timeout_expires(sk) - jiffies);
 	} else if (icsk_pending == ICSK_TIME_PROBE0) {
-		r->idiag_timer = 4;
+		r->idiag_timer = IDIAG_TIMER_PROBE0;
 		r->idiag_retrans = READ_ONCE(icsk->icsk_probes_out);
 		r->idiag_expires =
 			jiffies_delta_to_msecs(tcp_timeout_expires(sk) - jiffies);
 	} else if (timer_pending(&icsk->icsk_keepalive_timer)) {
-		r->idiag_timer = 2;
+		r->idiag_timer = IDIAG_TIMER_KEEPALIVE;
 		r->idiag_retrans = READ_ONCE(icsk->icsk_probes_out);
 		r->idiag_expires =
 			jiffies_delta_to_msecs(icsk->icsk_keepalive_timer.expires - jiffies);
+	} else if ((READ_ONCE(icsk->icsk_ack.pending) & ICSK_ACK_TIMER) &&
+		   timer_pending(&icsk->icsk_delack_timer)) {
+		r->idiag_timer = IDIAG_TIMER_DELACK;
+		r->idiag_expires =
+			jiffies_delta_to_msecs(icsk_delack_timeout(icsk) - jiffies);
 	}
 
 	if ((ext & (1 << (INET_DIAG_INFO - 1))) && handler->idiag_info_size) {
diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
index d83efd91f461c8ad0157faeebae051b32cb07bf4..4a316387414adaeb350b8d46ac0248833c3d111d 100644
--- a/net/ipv4/tcp_diag.c
+++ b/net/ipv4/tcp_diag.c
@@ -212,7 +212,7 @@ static int tcp_twsk_diag_fill(struct sock *sk,
 	r->idiag_retrans      = 0;
 
 	r->idiag_state	      = READ_ONCE(tw->tw_substate);
-	r->idiag_timer	      = 3;
+	r->idiag_timer	      = IDIAG_TIMER_TIMEWAIT;
 	tmo = tw->tw_timer.expires - jiffies;
 	r->idiag_expires      = jiffies_delta_to_msecs(tmo);
 	r->idiag_rqueue	      = 0;
@@ -247,7 +247,7 @@ static int tcp_req_diag_fill(struct sock *sk, struct sk_buff *skb,
 	r = nlmsg_data(nlh);
 	inet_diag_msg_common_fill(r, sk);
 	r->idiag_state = TCP_SYN_RECV;
-	r->idiag_timer = 1;
+	r->idiag_timer = IDIAG_TIMER_ON;
 	r->idiag_retrans = READ_ONCE(reqsk->num_retrans);
 
 	BUILD_BUG_ON(offsetof(struct inet_request_sock, ir_cookie) !=
-- 
2.53.0.473.g4a7958ca14-goog

Re: [PATCH v2 net-next] inet_diag: report delayed ack timer information

[Neal Cardwell]

On Thu, Mar 5, 2026 at 3:48 AM Eric Dumazet <edumazet@google.com> wrote:
>
> inet_sk_diag_fill() populates r->idiag_timer with the following
> precedence order:
>
> 1 - Retransmit timer.
> 4 - Probe0 timer.
> 2 - Keepalive timer.
>
> This patch adds a new value, last in the list, if other timers
> are not active.
>
> 5 - Delayed ACK timer.
>
> A corresponding iproute2 patch will follow to replace "unknown"
> with "delack":
>
> ESTAB 10     0   [2002:a05:6830:1f86::]:12875 [2002:a05:6830:1f85::]:50438
>
>     timer:(unknown,003ms,0) ino:152178 sk:3004 cgroup:unreachable:189 <->
>
>     skmem:(r1344,rb12780520,t0,tb262144,f2752,w0,o250,bl0,d0) ts usec_ts
>     ...
>
> Also add the following enum in uapi/linux/inet_diag.h
> as suggested by David Ahern.
>
> enum {
>         IDIAG_TIMER_OFF,
>         IDIAG_TIMER_ON,
>         IDIAG_TIMER_KEEPALIVE,
>         IDIAG_TIMER_TIMEWAIT,
>         IDIAG_TIMER_PROBE0,
>         IDIAG_TIMER_DELACK,
> };
>
> Neal Cardwell suggested to test for ICSK_ACK_TIMER:
> inet_csk_clear_xmit_timer() does not call sk_stop_timer()
> because INET_CSK_CLEAR_TIMERS is unset.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reviewed-by: David Ahern <dsahern@kernel.org>
> ---

Reviewed-by: Neal Cardwell <ncardwell@google.com>

Thanks, Eric!

neal

Re: [PATCH v2 net-next] inet_diag: report delayed ack timer information

[Kuniyuki Iwashima]

On Thu, Mar 5, 2026 at 3:48 AM Eric Dumazet <edumazet@google.com> wrote:
>
> inet_sk_diag_fill() populates r->idiag_timer with the following
> precedence order:
>
> 1 - Retransmit timer.
> 4 - Probe0 timer.
> 2 - Keepalive timer.
>
> This patch adds a new value, last in the list, if other timers
> are not active.
>
> 5 - Delayed ACK timer.
>
> A corresponding iproute2 patch will follow to replace "unknown"
> with "delack":
>
> ESTAB 10     0   [2002:a05:6830:1f86::]:12875 [2002:a05:6830:1f85::]:50438
>
>     timer:(unknown,003ms,0) ino:152178 sk:3004 cgroup:unreachable:189 <->
>
>     skmem:(r1344,rb12780520,t0,tb262144,f2752,w0,o250,bl0,d0) ts usec_ts
>     ...
>
> Also add the following enum in uapi/linux/inet_diag.h
> as suggested by David Ahern.
>
> enum {
>         IDIAG_TIMER_OFF,
>         IDIAG_TIMER_ON,
>         IDIAG_TIMER_KEEPALIVE,
>         IDIAG_TIMER_TIMEWAIT,
>         IDIAG_TIMER_PROBE0,
>         IDIAG_TIMER_DELACK,
> };
>
> Neal Cardwell suggested to test for ICSK_ACK_TIMER:
> inet_csk_clear_xmit_timer() does not call sk_stop_timer()
> because INET_CSK_CLEAR_TIMERS is unset.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reviewed-by: David Ahern <dsahern@kernel.org>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH v2 net-next] inet_diag: report delayed ack timer information

[patchwork-bot+netdevbpf]

Hello:

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

On Thu,  5 Mar 2026 11:48:29 +0000 you wrote:
> inet_sk_diag_fill() populates r->idiag_timer with the following
> precedence order:
> 
> 1 - Retransmit timer.
> 4 - Probe0 timer.
> 2 - Keepalive timer.
> 
> [...]

Here is the summary with links:
  - [v2,net-next] inet_diag: report delayed ack timer information
    https://git.kernel.org/netdev/net-next/c/c698f5cc940d

You are awesome, thank you!
-- 
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