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

[Eric Dumazet <edumazet@google.com>]

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":

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
    sack ecnseen bbr2s wscale:12,12 rto:10 rtt:4.073/0.205 ato:4 mss:4096
    pmtu:5000 rcvmss:536 advmss:4096 cwnd:48 ssthresh:48 bytes_sent:288980
    bytes_retrans:20 bytes_acked:288960 bytes_received:288970 segs_out:28986
    segs_in:30626 data_segs_out:28898 data_segs_in:28897
    bbr2:(bw:575Mbps,mrtt:0.049,bw_hi:1.48e+08Tbps,inflight_hi:48,
    extra_acked:1,mode:2,phase:PROBE_BW_UP,pacing_gain:1.25,cwnd_gain:2.25)
    send 386Mbps lastsnd:5 lastrcv:1 lastack:1 pacing_rate 711Mbps
    delivery_rate 575Mbps delivered:28898 app_limited busy:91010ms retrans:0/2
    dsack_dups:1 rcv_rtt:151640 rcv_space:266250 rcv_ssthresh:265904
    minrtt:0.049 snd_wnd:270336 rcv_wnd:266240 rehash:1

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/inet_diag.c | 4 ++++
 1 file changed, 4 insertions(+)

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;
+		r->idiag_expires =
+			jiffies_delta_to_msecs(icsk_delack_timeout(icsk) - jiffies);
 	}
 
 	if ((ext & (1 << (INET_DIAG_INFO - 1))) && handler->idiag_info_size) {
-- 
2.53.0.473.g4a7958ca14-goog