tcp: move tcp_rate_skb_delivered() to tcp_input.c

tcp_rate_skb_delivered() is only called from tcp_input.c.
Move it there and make it static.

Both gcc and clang are (auto)inlining it, TCP performance
is increased at a small space cost.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/2 grow/shrink: 3/0 up/down: 509/-187 (322)
Function                                     old     new   delta
tcp_sacktag_walk                            1682    1867    +185
tcp_ack                                     5230    5405    +175
tcp_shifted_skb                              437     586    +149
__pfx_tcp_rate_skb_delivered                  16       -     -16
tcp_rate_skb_delivered                       171       -    -171
Total: Before=22566192, After=22566514, chg +0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20260118123204.2315993-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 44 insertions, 46 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 15f9b20f851f..25143f156957 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1356,8 +1356,6 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
 void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
 
 /* From tcp_rate.c */
-void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
-			    struct rate_sample *rs);
 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
 		  bool is_sack_reneg, struct rate_sample *rs);
 void tcp_rate_check_app_limited(struct sock *sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 198f8a0d37be..dc8e256321b0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1637,6 +1637,50 @@ static u8 tcp_sacktag_one(struct sock *sk,
 	return sacked;
 }
 
+/* When an skb is sacked or acked, we fill in the rate sample with the (prior)
+ * delivery information when the skb was last transmitted.
+ *
+ * If an ACK (s)acks multiple skbs (e.g., stretched-acks), this function is
+ * called multiple times. We favor the information from the most recently
+ * sent skb, i.e., the skb with the most recently sent time and the highest
+ * sequence.
+ */
+static void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
+				   struct rate_sample *rs)
+{
+	struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
+	struct tcp_sock *tp = tcp_sk(sk);
+	u64 tx_tstamp;
+
+	if (!scb->tx.delivered_mstamp)
+		return;
+
+	tx_tstamp = tcp_skb_timestamp_us(skb);
+	if (!rs->prior_delivered ||
+	    tcp_skb_sent_after(tx_tstamp, tp->first_tx_mstamp,
+			       scb->end_seq, rs->last_end_seq)) {
+		rs->prior_delivered_ce  = scb->tx.delivered_ce;
+		rs->prior_delivered  = scb->tx.delivered;
+		rs->prior_mstamp     = scb->tx.delivered_mstamp;
+		rs->is_app_limited   = scb->tx.is_app_limited;
+		rs->is_retrans	     = scb->sacked & TCPCB_RETRANS;
+		rs->last_end_seq     = scb->end_seq;
+
+		/* Record send time of most recently ACKed packet: */
+		tp->first_tx_mstamp  = tx_tstamp;
+		/* Find the duration of the "send phase" of this window: */
+		rs->interval_us = tcp_stamp_us_delta(tp->first_tx_mstamp,
+						     scb->tx.first_tx_mstamp);
+
+	}
+	/* Mark off the skb delivered once it's sacked to avoid being
+	 * used again when it's cumulatively acked. For acked packets
+	 * we don't need to reset since it'll be freed soon.
+	 */
+	if (scb->sacked & TCPCB_SACKED_ACKED)
+		scb->tx.delivered_mstamp = 0;
+}
+
 /* Shift newly-SACKed bytes from this skb to the immediately previous
  * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
  */
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c
index 98eb346f986e..f0f2ef377043 100644
--- a/net/ipv4/tcp_rate.c
+++ b/net/ipv4/tcp_rate.c
@@ -34,50 +34,6 @@
  * ready to send in the write queue.
  */
 
-/* When an skb is sacked or acked, we fill in the rate sample with the (prior)
- * delivery information when the skb was last transmitted.
- *
- * If an ACK (s)acks multiple skbs (e.g., stretched-acks), this function is
- * called multiple times. We favor the information from the most recently
- * sent skb, i.e., the skb with the most recently sent time and the highest
- * sequence.
- */
-void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
-			    struct rate_sample *rs)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
-	u64 tx_tstamp;
-
-	if (!scb->tx.delivered_mstamp)
-		return;
-
-	tx_tstamp = tcp_skb_timestamp_us(skb);
-	if (!rs->prior_delivered ||
-	    tcp_skb_sent_after(tx_tstamp, tp->first_tx_mstamp,
-			       scb->end_seq, rs->last_end_seq)) {
-		rs->prior_delivered_ce  = scb->tx.delivered_ce;
-		rs->prior_delivered  = scb->tx.delivered;
-		rs->prior_mstamp     = scb->tx.delivered_mstamp;
-		rs->is_app_limited   = scb->tx.is_app_limited;
-		rs->is_retrans	     = scb->sacked & TCPCB_RETRANS;
-		rs->last_end_seq     = scb->end_seq;
-
-		/* Record send time of most recently ACKed packet: */
-		tp->first_tx_mstamp  = tx_tstamp;
-		/* Find the duration of the "send phase" of this window: */
-		rs->interval_us = tcp_stamp_us_delta(tp->first_tx_mstamp,
-						     scb->tx.first_tx_mstamp);
-
-	}
-	/* Mark off the skb delivered once it's sacked to avoid being
-	 * used again when it's cumulatively acked. For acked packets
-	 * we don't need to reset since it'll be freed soon.
-	 */
-	if (scb->sacked & TCPCB_SACKED_ACKED)
-		scb->tx.delivered_mstamp = 0;
-}
-
 /* Update the connection delivery information and generate a rate sample. */
 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
 		  bool is_sack_reneg, struct rate_sample *rs)