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

[David Ahern <dsahern@kernel.org>]

On 3/4/26 9:55 AM, Eric Dumazet wrote:
> On Wed, Mar 4, 2026 at 5:00 PM Eric Dumazet <edumazet@google.com> wrote:
>>
>> On Wed, Mar 4, 2026 at 4:48 PM David Ahern <dsahern@kernel.org> wrote:
>>>
>>> On 3/4/26 2:43 AM, Eric Dumazet 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 is needed to replace "unknown"
>>>> with "delack":
>>>
>>> ...
>>>
>>>> diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
>>>> index 9d215485b5c7e7ba29dd53c924f0245439d74af5..e4cb18061aefcc22df04644c00bf5c7db4e150d2 100644
>>>> --- a/net/ipv4/inet_diag.c
>>>> +++ b/net/ipv4/inet_diag.c
>>>> @@ -298,6 +298,10 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
>>>>               r->idiag_retrans = READ_ONCE(icsk->icsk_probes_out);
>>>>               r->idiag_expires =
>>>>                       jiffies_delta_to_msecs(icsk->icsk_keepalive_timer.expires - jiffies);
>>>> +     } else if (timer_pending(&icsk->icsk_delack_timer)) {
>>>> +             r->idiag_timer = 5;
>>>
>>> How come the idiag_timer values an enum in
>>> include/uapi/linux/inet_diag.h since this is a uapi?
>>
>> Yes, this can be done, although we survived all these years without it.
>>
>> Do you want to send a patch or should I implement this idea ?
> 
> I will squash in V2 :
> 
> 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 e4cb18061aefcc22df04644c00bf5c7db4e150d2..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;
> 
> @@ -284,22 +284,23 @@ 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 (timer_pending(&icsk->icsk_delack_timer)) {
> -               r->idiag_timer = 5;
> +       } 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);
>         }
> diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
> index d83efd91f461c8ad0157faeebae051b32cb07bf4..3e8ee2054466e109644a758f8b4f0a646e22e456
> 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;


thank you,.

Reviewed-by: David Ahern <dsahern@kernel.org>