tcp: add a @pace_delay parameter to tcp_reset_xmit_timer()

JIRA: https://issues.redhat.com/browse/RHEL-115191
Upstream Status: linux.git

commit 7baa030
Author: Eric Dumazet <edumazet@google.com>
Date:   Fri Feb 7 15:28:27 2025 +0000

    tcp: add a @pace_delay parameter to tcp_reset_xmit_timer()

    We want to factorize calls to inet_csk_reset_xmit_timer(),
    to ease TCP_RTO_MAX change.

    Current users want to add tcp_pacing_delay(sk)
    to the timeout.

    Remaining calls to inet_csk_reset_xmit_timer()
    do not add the pacing delay. Following patch
    will convert them, passing false for @pace_delay.

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
    Reviewed-by: Neal Cardwell <ncardwell@google.com>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Signed-off-by: Antoine Tenart <atenart@redhat.com>

Author: atenart

include/net/tcp.h

@@ -1354,10 +1354,12 @@ static inline unsigned long tcp_pacing_delay(const struct sock *sk)
 
 static inline void tcp_reset_xmit_timer(struct sock *sk,
 					const int what,
-					unsigned long when)
+					unsigned long when,
+					bool pace_delay)
 {
-	inet_csk_reset_xmit_timer(sk, what, when + tcp_pacing_delay(sk),
-				  TCP_RTO_MAX);
+	if (pace_delay)
+		when += tcp_pacing_delay(sk);
+	inet_csk_reset_xmit_timer(sk, what, when, TCP_RTO_MAX);
 }
 
 /* Something is really bad, we could not queue an additional packet,
@@ -1386,7 +1388,7 @@ static inline void tcp_check_probe_timer(struct sock *sk)
 {
 	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
 		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-				     tcp_probe0_base(sk));
+				     tcp_probe0_base(sk), true);
 }
 
 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)

net/ipv4/tcp_input.c

@@ -3231,7 +3231,7 @@ void tcp_rearm_rto(struct sock *sk)
 			 */
 			rto = usecs_to_jiffies(max_t(int, delta_us, 1));
 		}
-		tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto);
+		tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto, true);
 	}
 }
 
@@ -3512,7 +3512,7 @@ static void tcp_ack_probe(struct sock *sk)
 		unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
 
 		when = tcp_clamp_probe0_to_user_timeout(sk, when);
-		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when);
+		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when, true);
 	}
 }
 

net/ipv4/tcp_output.c

@@ -2787,7 +2787,7 @@ bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
 	if (rto_delta_us > 0)
 		timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
 
-	tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout);
+	tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, true);
 	return true;
 }
 
@@ -3424,7 +3424,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 	}
 	if (rearm_timer)
 		tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
-				     inet_csk(sk)->icsk_rto);
+				     inet_csk(sk)->icsk_rto, true);
 }
 
 /* We allow to exceed memory limits for FIN packets to expedite
@@ -4176,7 +4176,7 @@ void tcp_send_probe0(struct sock *sk)
 	}
 
 	timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
-	tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout);
+	tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, true);
 }
 
 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)