rxrpc: Provide kernel interface to set max lifespan on a call

Provide an interface to set max lifespan on a call from inside of the
kernel without having to call kernel_sendmsg().
Signed-off-by: David Howells <dhowells@redhat.com>

Documentation/networking/rxrpc.txt

@@ -1056,6 +1056,16 @@ The kernel interface functions are as follows:
      This value can be used to determine if the remote client has been
      restarted as it shouldn't change otherwise.
 
+ (*) Set the maxmimum lifespan on a call.
+
+	void rxrpc_kernel_set_max_life(struct socket *sock,
+				       struct rxrpc_call *call,
+				       unsigned long hard_timeout)
+
+     This sets the maximum lifespan on a call to hard_timeout (which is in
+     jiffies).  In the event of the timeout occurring, the call will be
+     aborted and -ETIME or -ETIMEDOUT will be returned.
+
 
 =======================
 CONFIGURABLE PARAMETERS

include/net/af_rxrpc.h

@@ -68,5 +68,7 @@ u32 rxrpc_kernel_get_epoch(struct socket *, struct rxrpc_call *);
 bool rxrpc_kernel_get_reply_time(struct socket *, struct rxrpc_call *,
 				 ktime_t *);
 bool rxrpc_kernel_call_is_complete(struct rxrpc_call *);
+void rxrpc_kernel_set_max_life(struct socket *, struct rxrpc_call *,
+			       unsigned long);
 
 #endif /* _NET_RXRPC_H */

net/rxrpc/af_rxrpc.c

@@ -443,6 +443,31 @@ void rxrpc_kernel_new_call_notification(
 }
 EXPORT_SYMBOL(rxrpc_kernel_new_call_notification);
 
+/**
+ * rxrpc_kernel_set_max_life - Set maximum lifespan on a call
+ * @sock: The socket the call is on
+ * @call: The call to configure
+ * @hard_timeout: The maximum lifespan of the call in jiffies
+ *
+ * Set the maximum lifespan of a call.  The call will end with ETIME or
+ * ETIMEDOUT if it takes longer than this.
+ */
+void rxrpc_kernel_set_max_life(struct socket *sock, struct rxrpc_call *call,
+			       unsigned long hard_timeout)
+{
+	unsigned long now;
+
+	mutex_lock(&call->user_mutex);
+
+	now = jiffies;
+	hard_timeout += now;
+	WRITE_ONCE(call->expect_term_by, hard_timeout);
+	rxrpc_reduce_call_timer(call, hard_timeout, now, rxrpc_timer_set_for_hard);
+
+	mutex_unlock(&call->user_mutex);
+}
+EXPORT_SYMBOL(rxrpc_kernel_set_max_life);
+
 /*
  * connect an RxRPC socket
  * - this just targets it at a specific destination; no actual connection