af_rxrpc: Add sysctls for configuring RxRPC parameters

Add sysctls for configuring RxRPC protocol handling, specifically controls on
delays before ack generation, the delay before resending a packet, the maximum
lifetime of a call and the expiration times of calls, connections and
transports that haven't been recently used.

More info added in Documentation/networking/rxrpc.txt.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 28 insertions, 7 deletions

diff --git a/net/rxrpc/ar-ack.c b/net/rxrpc/ar-ack.c
index cd97a0ce48d8..732b82f540c5 100644
--- a/net/rxrpc/ar-ack.c
+++ b/net/rxrpc/ar-ack.c
@@ -19,7 +19,29 @@
 #include <net/af_rxrpc.h>
 #include "ar-internal.h"
 
-static unsigned int rxrpc_ack_defer = 1;
+/*
+ * How long to wait before scheduling ACK generation after seeing a
+ * packet with RXRPC_REQUEST_ACK set (in jiffies).
+ */
+unsigned rxrpc_requested_ack_delay = 1;
+
+/*
+ * How long to wait before scheduling an ACK with subtype DELAY (in jiffies).
+ *
+ * We use this when we've received new data packets.  If those packets aren't
+ * all consumed within this time we will send a DELAY ACK if an ACK was not
+ * requested to let the sender know it doesn't need to resend.
+ */
+unsigned rxrpc_soft_ack_delay = 1 * HZ;
+
+/*
+ * How long to wait before scheduling an ACK with subtype IDLE (in jiffies).
+ *
+ * We use this when we've consumed some previously soft-ACK'd packets when
+ * further packets aren't immediately received to decide when to send an IDLE
+ * ACK let the other end know that it can free up its Tx buffer space.
+ */
+unsigned rxrpc_idle_ack_delay = 1;
 
 static const char *rxrpc_acks(u8 reason)
 {
@@ -82,24 +104,23 @@ void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
         switch (ack_reason) {
         case RXRPC_ACK_DELAY:
                 _debug("run delay timer");
-                call->ack_timer.expires = jiffies + rxrpc_ack_timeout * HZ;
-                add_timer(&call->ack_timer);
-                return;
+                expiry = rxrpc_soft_ack_delay;
+                goto run_timer;
 
         case RXRPC_ACK_IDLE:
                 if (!immediate) {
                         _debug("run defer timer");
-                        expiry = 1;
+                        expiry = rxrpc_idle_ack_delay;
                         goto run_timer;
                 }
                 goto cancel_timer;
 
         case RXRPC_ACK_REQUESTED:
-                if (!rxrpc_ack_defer)
+                expiry = rxrpc_requested_ack_delay;
+                if (!expiry)
                         goto cancel_timer;
                 if (!immediate || serial == cpu_to_be32(1)) {
                         _debug("run defer timer");
-                        expiry = rxrpc_ack_defer;
                         goto run_timer;
                 }