af_rxrpc: Expose more RxRPC parameters via sysctls

Expose RxRPC parameters via sysctls to control the Rx window size, the Rx MTU
maximum size and the number of packets that can be glued into a jumbo packet.

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

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

4 files changed, 60 insertions, 4 deletions

diff --git a/net/rxrpc/ar-ack.c b/net/rxrpc/ar-ack.c
index 1a490d976e7e..c6be17a959a6 100644
--- a/net/rxrpc/ar-ack.c
+++ b/net/rxrpc/ar-ack.c
@@ -43,6 +43,26 @@ unsigned rxrpc_soft_ack_delay = 1 * HZ;
  */
 unsigned rxrpc_idle_ack_delay = 0.5 * HZ;
 
+/*
+ * Receive window size in packets.  This indicates the maximum number of
+ * unconsumed received packets we're willing to retain in memory.  Once this
+ * limit is hit, we should generate an EXCEEDS_WINDOW ACK and discard further
+ * packets.
+ */
+unsigned rxrpc_rx_window_size = 32;
+
+/*
+ * Maximum Rx MTU size.  This indicates to the sender the size of jumbo packet
+ * made by gluing normal packets together that we're willing to handle.
+ */
+unsigned rxrpc_rx_mtu = 5692;
+
+/*
+ * The maximum number of fragments in a received jumbo packet that we tell the
+ * sender that we're willing to handle.
+ */
+unsigned rxrpc_rx_jumbo_max = 4;
+
 static const char *rxrpc_acks(u8 reason)
 {
         static const char *const str[] = {
@@ -1195,11 +1215,11 @@ send_ACK:
         mtu = call->conn->trans->peer->if_mtu;
         mtu -= call->conn->trans->peer->hdrsize;
         ackinfo.maxMTU  = htonl(mtu);
-        ackinfo.rwind   = htonl(32);
+        ackinfo.rwind   = htonl(rxrpc_rx_window_size);
 
         /* permit the peer to send us jumbo packets if it wants to */
-        ackinfo.rxMTU   = htonl(5692);
-        ackinfo.jumbo_max = htonl(4);
+        ackinfo.rxMTU   = htonl(rxrpc_rx_mtu);
+        ackinfo.jumbo_max = htonl(rxrpc_rx_jumbo_max);
 
         hdr.serial = htonl(atomic_inc_return(&call->conn->serial));
         _proto("Tx ACK %%%u { m=%hu f=#%u p=#%u s=%%%u r=%s n=%u }",
diff --git a/net/rxrpc/ar-call.c b/net/rxrpc/ar-call.c
index 1e0903a2a0db..6e4d58c9b042 100644
--- a/net/rxrpc/ar-call.c
+++ b/net/rxrpc/ar-call.c
@@ -99,7 +99,7 @@ static struct rxrpc_call *rxrpc_alloc_call(gfp_t gfp)
         call->rx_data_expect = 1;
         call->rx_data_eaten = 0;
         call->rx_first_oos = 0;
-        call->ackr_win_top = call->rx_data_eaten + 1 + RXRPC_MAXACKS;
+        call->ackr_win_top = call->rx_data_eaten + 1 + rxrpc_rx_window_size;
         call->creation_jif = jiffies;
         return call;
 }
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 036e1dd84223..1ecd070e9149 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -436,6 +436,9 @@ int rxrpc_reject_call(struct rxrpc_sock *);
 extern unsigned rxrpc_requested_ack_delay;
 extern unsigned rxrpc_soft_ack_delay;
 extern unsigned rxrpc_idle_ack_delay;
+extern unsigned rxrpc_rx_window_size;
+extern unsigned rxrpc_rx_mtu;
+extern unsigned rxrpc_rx_jumbo_max;
 
 void __rxrpc_propose_ACK(struct rxrpc_call *, u8, __be32, bool);
 void rxrpc_propose_ACK(struct rxrpc_call *, u8, __be32, bool);
diff --git a/net/rxrpc/sysctl.c b/net/rxrpc/sysctl.c
index cdc85e72af5d..50a98a910eb1 100644
--- a/net/rxrpc/sysctl.c
+++ b/net/rxrpc/sysctl.c
@@ -17,6 +17,9 @@
 static struct ctl_table_header *rxrpc_sysctl_reg_table;
 static const unsigned zero = 0;
 static const unsigned one = 1;
+static const unsigned four = 4;
+static const unsigned n_65535 = 65535;
+static const unsigned n_max_acks = RXRPC_MAXACKS;
 
 /*
  * RxRPC operating parameters.
@@ -94,6 +97,36 @@ static struct ctl_table rxrpc_sysctl_table[] = {
                 .proc_handler   = proc_dointvec_minmax,
                 .extra1         = (void *)&one,
         },
+
+        /* Non-time values */
+        {
+                .procname       = "rx_window_size",
+                .data           = &rxrpc_rx_window_size,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = (void *)&one,
+                .extra2         = (void *)&n_max_acks,
+        },
+        {
+                .procname       = "rx_mtu",
+                .data           = &rxrpc_rx_mtu,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = (void *)&one,
+                .extra1         = (void *)&n_65535,
+        },
+        {
+                .procname       = "rx_jumbo_max",
+                .data           = &rxrpc_rx_jumbo_max,
+                .maxlen         = sizeof(unsigned),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = (void *)&one,
+                .extra2         = (void *)&four,
+        },
+
         { }
 };