rxrpc: Implement an in-kernel rxperf server for testing purposes

Implement an in-kernel rxperf server to allow kernel-based rxrpc services
to be tested directly, unlike with AFS where they're accessed by the
fileserver when the latter decides it wants to.

This is implemented as a module that, if loaded, opens UDP port 7009
(afs3-rmtsys) and listens on it for incoming calls.  Calls can be generated
using the rxperf command shipped with OpenAFS, for example.

Changes
=======
ver #2)
 - Use min_t() instead of min().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: Jakub Kicinski <kuba@kernel.org>

include/net/af_rxrpc.h

@@ -71,5 +71,6 @@ void rxrpc_kernel_set_max_life(struct socket *, struct rxrpc_call *,
 			       unsigned long);
 
 int rxrpc_sock_set_min_security_level(struct sock *sk, unsigned int val);
+int rxrpc_sock_set_security_keyring(struct sock *, struct key *);
 
 #endif /* _NET_RXRPC_H */

net/rxrpc/Kconfig

@@ -58,4 +58,11 @@ config RXKAD
 
 	  See Documentation/networking/rxrpc.rst.
 
+config RXPERF
+	tristate "RxRPC test service"
+	help
+	  Provide an rxperf service tester.  This listens on UDP port 7009 for
+	  incoming calls from the rxperf program (an example of which can be
+	  found in OpenAFS).
+
 endif

net/rxrpc/Makefile

@@ -36,3 +36,6 @@ rxrpc-y := \
 rxrpc-$(CONFIG_PROC_FS) += proc.o
 rxrpc-$(CONFIG_RXKAD) += rxkad.o
 rxrpc-$(CONFIG_SYSCTL) += sysctl.o
+
+
+obj-$(CONFIG_RXPERF) += rxperf.o