diff mbox series

[net-next,v4,4/4] net: tcp: refactor the dbg message in tcp_retransmit_timer()

Message ID 20230811025530.3510703-5-imagedong@tencent.com
State New
Headers
Series net: tcp: support probing OOM |

Commit Message

Menglong Dong Aug. 11, 2023, 2:55 a.m. UTC 
  From: Menglong Dong <imagedong@tencent.com>

The debug message in tcp_retransmit_timer() is slightly wrong, because
they could be printed even if we did not receive a new ACK packet from
the remote peer.

Change it to probing zero-window, as it is a expected case now. The
description may be not correct.

Adding the duration since the last ACK we received, and the duration of
the retransmission, which are useful for debugging.

And the message now like this:

Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 209ms ago, lasting 209ms
Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 404ms ago, lasting 408ms
Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 812ms ago, lasting 1224ms

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
 net/ipv4/tcp_timer.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

Comments

Eric Dumazet Aug. 11, 2023, 7:38 a.m. UTC | #1 
On Fri, Aug 11, 2023 at 5:01 AM <menglong8.dong@gmail.com> wrote:
>
> From: Menglong Dong <imagedong@tencent.com>
>
> The debug message in tcp_retransmit_timer() is slightly wrong, because
> they could be printed even if we did not receive a new ACK packet from
> the remote peer.
>
> Change it to probing zero-window, as it is a expected case now. The
> description may be not correct.
>
> Adding the duration since the last ACK we received, and the duration of
> the retransmission, which are useful for debugging.
>
> And the message now like this:
>
> Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 209ms ago, lasting 209ms
> Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 404ms ago, lasting 408ms
> Probing zero-window on 127.0.0.1:9999/46946, seq=3737778959:3737791503, recv 812ms ago, lasting 1224ms

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

Patch

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index f2a52c11e044..74c70fc1003c 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -519,20 +519,23 @@  void tcp_retransmit_timer(struct sock *sk)
 		 * we cannot allow such beasts to hang infinitely.
 		 */
 		struct inet_sock *inet = inet_sk(sk);
+		u32 rtx_delta;
+
+		rtx_delta = tcp_time_stamp(tp) - (tp->retrans_stamp ?: tcp_skb_timestamp(skb));
 		if (sk->sk_family == AF_INET) {
-			net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
-					    &inet->inet_daddr,
-					    ntohs(inet->inet_dport),
-					    inet->inet_num,
-					    tp->snd_una, tp->snd_nxt);
+			net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n",
+				&inet->inet_daddr, ntohs(inet->inet_dport),
+				inet->inet_num, tp->snd_una, tp->snd_nxt,
+				jiffies_to_msecs(jiffies - tp->rcv_tstamp),
+				rtx_delta);
 		}
 #if IS_ENABLED(CONFIG_IPV6)
 		else if (sk->sk_family == AF_INET6) {
-			net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
-					    &sk->sk_v6_daddr,
-					    ntohs(inet->inet_dport),
-					    inet->inet_num,
-					    tp->snd_una, tp->snd_nxt);
+			net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n",
+				&sk->sk_v6_daddr, ntohs(inet->inet_dport),
+				inet->inet_num, tp->snd_una, tp->snd_nxt,
+				jiffies_to_msecs(jiffies - tp->rcv_tstamp),
+				rtx_delta);
 		}
 #endif
 		if (tcp_rtx_probe0_timed_out(sk, skb)) {