inet_diag: report delayed ack timer information

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>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260305114829.2163276-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 20 insertions, 6 deletions

diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h
index 86bb2e8b17c9..21f0d735fbae 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 9d215485b5c7..34b77aa87d0a 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 7935702e394b..ba1fdbe9807f 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) !=