rxrpc: Allow failed client calls to be retried

Allow a client call that failed on network error to be retried, provided
that the Tx queue still holds DATA packet 1.  This allows an operation to
be submitted to another server or another address for the same server
without having to repackage and re-encrypt the data so far processed.

Two new functions are provided:

 (1) rxrpc_kernel_check_call() - This is used to find out the completion
     state of a call to guess whether it can be retried and whether it
     should be retried.

 (2) rxrpc_kernel_retry_call() - Disconnect the call from its current
     connection, reset the state and submit it as a new client call to a
     new address.  The new address need not match the previous address.

A call may be retried even if all the data hasn't been loaded into it yet;
a partially constructed will be retained at the same point it was at when
an error condition was detected.  msg_data_left() can be used to find out
how much data was packaged before the error occurred.

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

1 files changed, 69 insertions, 0 deletions

diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index 31e97f714ca9..fb17552fd292 100644
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -337,6 +337,75 @@ void rxrpc_kernel_end_call(struct socket *sock, struct rxrpc_call *call)
 EXPORT_SYMBOL(rxrpc_kernel_end_call);
 
 /**
+ * rxrpc_kernel_check_call - Check a call's state
+ * @sock: The socket the call is on
+ * @call: The call to check
+ * @_compl: Where to store the completion state
+ * @_abort_code: Where to store any abort code
+ *
+ * Allow a kernel service to query the state of a call and find out the manner
+ * of its termination if it has completed.  Returns -EINPROGRESS if the call is
+ * still going, 0 if the call finished successfully, -ECONNABORTED if the call
+ * was aborted and an appropriate error if the call failed in some other way.
+ */
+int rxrpc_kernel_check_call(struct socket *sock, struct rxrpc_call *call,
+			    enum rxrpc_call_completion *_compl, u32 *_abort_code)
+{
+	if (call->state != RXRPC_CALL_COMPLETE)
+		return -EINPROGRESS;
+	smp_rmb();
+	*_compl = call->completion;
+	*_abort_code = call->abort_code;
+	return call->error;
+}
+EXPORT_SYMBOL(rxrpc_kernel_check_call);
+
+/**
+ * rxrpc_kernel_retry_call - Allow a kernel service to retry a call
+ * @sock: The socket the call is on
+ * @call: The call to retry
+ * @srx: The address of the peer to contact
+ * @key: The security context to use (defaults to socket setting)
+ *
+ * Allow a kernel service to try resending a client call that failed due to a
+ * network error to a new address.  The Tx queue is maintained intact, thereby
+ * relieving the need to re-encrypt any request data that has already been
+ * buffered.
+ */
+int rxrpc_kernel_retry_call(struct socket *sock, struct rxrpc_call *call,
+			    struct sockaddr_rxrpc *srx, struct key *key)
+{
+	struct rxrpc_conn_parameters cp;
+	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
+	int ret;
+
+	_enter("%d{%d}", call->debug_id, atomic_read(&call->usage));
+
+	if (!key)
+		key = rx->key;
+	if (key && !key->payload.data[0])
+		key = NULL; /* a no-security key */
+
+	memset(&cp, 0, sizeof(cp));
+	cp.local		= rx->local;
+	cp.key			= key;
+	cp.security_level	= 0;
+	cp.exclusive		= false;
+	cp.service_id		= srx->srx_service;
+
+	mutex_lock(&call->user_mutex);
+
+	ret = rxrpc_prepare_call_for_retry(rx, call);
+	if (ret == 0)
+		ret = rxrpc_retry_client_call(rx, call, &cp, srx, GFP_KERNEL);
+
+	mutex_unlock(&call->user_mutex);
+	_leave(" = %d", ret);
+	return ret;
+}
+EXPORT_SYMBOL(rxrpc_kernel_retry_call);
+
+/**
  * rxrpc_kernel_new_call_notification - Get notifications of new calls
  * @sock: The socket to intercept received messages on
  * @notify_new_call: Function to be called when new calls appear