rxrpc: Add config to inject packet loss

Add a configuration option to inject packet loss by discarding
approximately every 8th packet received and approximately every 8th DATA
packet transmitted.

Note that no locking is used, but it shouldn't really matter.
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/Kconfig

@@ -26,6 +26,13 @@ config AF_RXRPC_IPV6
 	  Say Y here to allow AF_RXRPC to use IPV6 UDP as well as IPV4 UDP as
 	  its network transport.
 
+config AF_RXRPC_INJECT_LOSS
+	bool "Inject packet loss into RxRPC packet stream"
+	depends on AF_RXRPC
+	help
+	  Say Y here to inject packet loss by discarding some received and some
+	  transmitted packets.
+
 
 config AF_RXRPC_DEBUG
 	bool "RxRPC dynamic debugging"

net/rxrpc/input.c

@@ -712,6 +712,14 @@ void rxrpc_data_ready(struct sock *udp_sk)
 	skb_orphan(skb);
 	sp = rxrpc_skb(skb);
 
+	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
+		static int lose;
+		if ((lose++ & 7) == 7) {
+			rxrpc_lose_skb(skb, rxrpc_skb_rx_lost);
+			return;
+		}
+	}
+
 	_net("Rx UDP packet from %08x:%04hu",
 	     ntohl(ip_hdr(skb)->saddr), ntohs(udp_hdr(skb)->source));
 

net/rxrpc/output.c

@@ -225,6 +225,15 @@ int rxrpc_send_data_packet(struct rxrpc_connection *conn, struct sk_buff *skb)
 	msg.msg_controllen = 0;
 	msg.msg_flags = 0;
 
+	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
+		static int lose;
+		if ((lose++ & 7) == 7) {
+			rxrpc_lose_skb(skb, rxrpc_skb_tx_lost);
+			_leave(" = 0 [lose]");
+			return 0;
+		}
+	}
+
 	/* send the packet with the don't fragment bit set if we currently
 	 * think it's small enough */
 	if (skb->len - sizeof(struct rxrpc_wire_header) < conn->params.peer->maxdata) {