rxrpc: Obtain RTT data by requesting ACKs on DATA packets
In addition to sending a PING ACK to gain RTT data, we can set the
RXRPC_REQUEST_ACK flag on a DATA packet and get a REQUESTED-ACK ACK. The
ACK packet contains the serial number of the packet it is in response to,
so we can look through the Tx buffer for a matching DATA packet.
This requires that the data packets be stamped with the time of
transmission as a ktime rather than having the resend_at time in jiffies.
This further requires the resend code to do the resend determination in
ktimes and convert to jiffies to set the timer.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index a0a5bd1..c121949 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -356,6 +356,38 @@
}
/*
+ * Process a requested ACK.
+ */
+static void rxrpc_input_requested_ack(struct rxrpc_call *call,
+ ktime_t resp_time,
+ rxrpc_serial_t orig_serial,
+ rxrpc_serial_t ack_serial)
+{
+ struct rxrpc_skb_priv *sp;
+ struct sk_buff *skb;
+ ktime_t sent_at;
+ int ix;
+
+ for (ix = 0; ix < RXRPC_RXTX_BUFF_SIZE; ix++) {
+ skb = call->rxtx_buffer[ix];
+ if (!skb)
+ continue;
+
+ sp = rxrpc_skb(skb);
+ if (sp->hdr.serial != orig_serial)
+ continue;
+ smp_rmb();
+ sent_at = skb->tstamp;
+ goto found;
+ }
+ return;
+
+found:
+ rxrpc_peer_add_rtt(call, rxrpc_rtt_rx_requested_ack,
+ orig_serial, ack_serial, sent_at, resp_time);
+}
+
+/*
* Process a ping response.
*/
static void rxrpc_input_ping_response(struct rxrpc_call *call,
@@ -508,6 +540,9 @@
if (buf.ack.reason == RXRPC_ACK_PING_RESPONSE)
rxrpc_input_ping_response(call, skb->tstamp, acked_serial,
sp->hdr.serial);
+ if (buf.ack.reason == RXRPC_ACK_REQUESTED)
+ rxrpc_input_requested_ack(call, skb->tstamp, acked_serial,
+ sp->hdr.serial);
if (buf.ack.reason == RXRPC_ACK_PING) {
_proto("Rx ACK %%%u PING Request", sp->hdr.serial);