Merge branch 'rxrpc-miscellaneous-fixes'

David Howells says:

====================
rxrpc: Miscellaneous fixes (part)

Here some miscellaneous fixes for AF_RXRPC:

 (1) Fix the congestion control algorithm to start cwnd at 4 and to not cut
     ssthresh when the peer cuts its rwind size.

 (2) Only transmit a single ACK for all the DATA packets glued together
     into a jumbo packet to reduce the number of ACKs being generated.
====================

Link: https://lore.kernel.org/r/20240503150749.1001323-1-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/rxrpc/ar-internal.h

@@ -697,7 +697,7 @@ struct rxrpc_call {
 	 * packets) rather than bytes.
 	 */
 #define RXRPC_TX_SMSS		RXRPC_JUMBO_DATALEN
-#define RXRPC_MIN_CWND		(RXRPC_TX_SMSS > 2190 ? 2 : RXRPC_TX_SMSS > 1095 ? 3 : 4)
+#define RXRPC_MIN_CWND		4
 	u8			cong_cwnd;	/* Congestion window size */
 	u8			cong_extra;	/* Extra to send for congestion management */
 	u8			cong_ssthresh;	/* Slow-start threshold */

net/rxrpc/call_object.c

@@ -174,12 +174,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp,
 	call->rx_winsize = rxrpc_rx_window_size;
 	call->tx_winsize = 16;
 
-	if (RXRPC_TX_SMSS > 2190)
-		call->cong_cwnd = 2;
-	else if (RXRPC_TX_SMSS > 1095)
-		call->cong_cwnd = 3;
-	else
-		call->cong_cwnd = 4;
+	call->cong_cwnd = RXRPC_MIN_CWND;
 	call->cong_ssthresh = RXRPC_TX_MAX_WINDOW;
 
 	call->rxnet = rxnet;

net/rxrpc/input.c

@@ -9,6 +9,17 @@
 
 #include "ar-internal.h"
 
+/* Override priority when generating ACKs for received DATA */
+static const u8 rxrpc_ack_priority[RXRPC_ACK__INVALID] = {
+	[RXRPC_ACK_IDLE]		= 1,
+	[RXRPC_ACK_DELAY]		= 2,
+	[RXRPC_ACK_REQUESTED]		= 3,
+	[RXRPC_ACK_DUPLICATE]		= 4,
+	[RXRPC_ACK_EXCEEDS_WINDOW]	= 5,
+	[RXRPC_ACK_NOSPACE]		= 6,
+	[RXRPC_ACK_OUT_OF_SEQUENCE]	= 7,
+};
+
 static void rxrpc_proto_abort(struct rxrpc_call *call, rxrpc_seq_t seq,
 			      enum rxrpc_abort_reason why)
 {
@@ -365,7 +376,7 @@ static void rxrpc_input_queue_data(struct rxrpc_call *call, struct sk_buff *skb,
  * Process a DATA packet.
  */
 static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
-				 bool *_notify)
+				 bool *_notify, rxrpc_serial_t *_ack_serial, int *_ack_reason)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct sk_buff *oos;
@@ -418,8 +429,6 @@ static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
 		/* Send an immediate ACK if we fill in a hole */
 		else if (!skb_queue_empty(&call->rx_oos_queue))
 			ack_reason = RXRPC_ACK_DELAY;
-		else
-			call->ackr_nr_unacked++;
 
 		window++;
 		if (after(window, wtop)) {
@@ -497,12 +506,16 @@ static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
 	}
 
 send_ack:
-	if (ack_reason >= 0)
-		rxrpc_send_ACK(call, ack_reason, serial,
-			       rxrpc_propose_ack_input_data);
-	else
-		rxrpc_propose_delay_ACK(call, serial,
-					rxrpc_propose_ack_input_data);
+	if (ack_reason >= 0) {
+		if (rxrpc_ack_priority[ack_reason] > rxrpc_ack_priority[*_ack_reason]) {
+			*_ack_serial = serial;
+			*_ack_reason = ack_reason;
+		} else if (rxrpc_ack_priority[ack_reason] == rxrpc_ack_priority[*_ack_reason] &&
+			   ack_reason == RXRPC_ACK_REQUESTED) {
+			*_ack_serial = serial;
+			*_ack_reason = ack_reason;
+		}
+	}
 }
 
 /*
@@ -513,9 +526,11 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb
 	struct rxrpc_jumbo_header jhdr;
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb), *jsp;
 	struct sk_buff *jskb;
+	rxrpc_serial_t ack_serial = 0;
 	unsigned int offset = sizeof(struct rxrpc_wire_header);
 	unsigned int len = skb->len - offset;
 	bool notify = false;
+	int ack_reason = 0;
 
 	while (sp->hdr.flags & RXRPC_JUMBO_PACKET) {
 		if (len < RXRPC_JUMBO_SUBPKTLEN)
@@ -535,7 +550,7 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb
 		jsp = rxrpc_skb(jskb);
 		jsp->offset = offset;
 		jsp->len = RXRPC_JUMBO_DATALEN;
-		rxrpc_input_data_one(call, jskb, &notify);
+		rxrpc_input_data_one(call, jskb, &notify, &ack_serial, &ack_reason);
 		rxrpc_free_skb(jskb, rxrpc_skb_put_jumbo_subpacket);
 
 		sp->hdr.flags = jhdr.flags;
@@ -548,7 +563,16 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb
 
 	sp->offset = offset;
 	sp->len    = len;
-	rxrpc_input_data_one(call, skb, &notify);
+	rxrpc_input_data_one(call, skb, &notify, &ack_serial, &ack_reason);
+
+	if (ack_reason > 0) {
+		rxrpc_send_ACK(call, ack_reason, ack_serial,
+			       rxrpc_propose_ack_input_data);
+	} else {
+		call->ackr_nr_unacked++;
+		rxrpc_propose_delay_ACK(call, sp->hdr.serial,
+					rxrpc_propose_ack_input_data);
+	}
 	if (notify) {
 		trace_rxrpc_notify_socket(call->debug_id, sp->hdr.serial);
 		rxrpc_notify_socket(call);
@@ -685,9 +709,6 @@ static void rxrpc_input_ack_trailer(struct rxrpc_call *call, struct sk_buff *skb
 		call->tx_winsize = rwind;
 	}
 
-	if (call->cong_ssthresh > rwind)
-		call->cong_ssthresh = rwind;
-
 	mtu = min(ntohl(trailer->maxMTU), ntohl(trailer->ifMTU));
 
 	peer = call->peer;