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

net/rxrpc/server_key.c

@@ -144,3 +144,28 @@ int rxrpc_server_keyring(struct rxrpc_sock *rx, sockptr_t optval, int optlen)
 	_leave(" = 0 [key %x]", key->serial);
 	return 0;
 }
+
+/**
+ * rxrpc_sock_set_security_keyring - Set the security keyring for a kernel service
+ * @sk: The socket to set the keyring on
+ * @keyring: The keyring to set
+ *
+ * Set the server security keyring on an rxrpc socket.  This is used to provide
+ * the encryption keys for a kernel service.
+ */
+int rxrpc_sock_set_security_keyring(struct sock *sk, struct key *keyring)
+{
+	struct rxrpc_sock *rx = rxrpc_sk(sk);
+	int ret = 0;
+
+	lock_sock(sk);
+	if (rx->securities)
+		ret = -EINVAL;
+	else if (rx->sk.sk_state != RXRPC_UNBOUND)
+		ret = -EISCONN;
+	else
+		rx->securities = key_get(keyring);
+	release_sock(sk);
+	return ret;
+}
+EXPORT_SYMBOL(rxrpc_sock_set_security_keyring);