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, 45 insertions, 0 deletions

diff --git a/Documentation/networking/rxrpc.txt b/Documentation/networking/rxrpc.txt
index 92a3c3bd5ac3..810620153a44 100644
--- a/Documentation/networking/rxrpc.txt
+++ b/Documentation/networking/rxrpc.txt
@@ -975,6 +975,51 @@ The kernel interface functions are as follows:
      size should be set when the call is begun.  tx_total_len may not be less
      than zero.
 
+ (*) Check to see the completion state of a call so that the caller can assess
+     whether it needs to be retried.
+
+	enum rxrpc_call_completion {
+		RXRPC_CALL_SUCCEEDED,
+		RXRPC_CALL_REMOTELY_ABORTED,
+		RXRPC_CALL_LOCALLY_ABORTED,
+		RXRPC_CALL_LOCAL_ERROR,
+		RXRPC_CALL_NETWORK_ERROR,
+	};
+
+	int rxrpc_kernel_check_call(struct socket *sock, struct rxrpc_call *call,
+				    enum rxrpc_call_completion *_compl,
+				    u32 *_abort_code);
+
+     On return, -EINPROGRESS will be returned if the call is still ongoing; if
+     it is finished, *_compl will be set to indicate the manner of completion,
+     *_abort_code will be set to any abort code that occurred.  0 will be
+     returned on a successful completion, -ECONNABORTED will be returned if the
+     client failed due to a remote abort and anything else will return an
+     appropriate error code.
+
+     The caller should look at this information to decide if it's worth
+     retrying the call.
+
+ (*) Retry a client call.
+
+	int rxrpc_kernel_retry_call(struct socket *sock,
+				    struct rxrpc_call *call,
+				    struct sockaddr_rxrpc *srx,
+				    struct key *key);
+
+     This attempts to partially reinitialise a call and submit it again whilst
+     reusing the original call's Tx queue to avoid the need to repackage and
+     re-encrypt the data to be sent.  call indicates the call to retry, srx the
+     new address to send it to and key the encryption key to use for signing or
+     encrypting the packets.
+
+     For this to work, the first Tx data packet must still be in the transmit
+     queue, and currently this is only permitted for local and network errors
+     and the call must not have been aborted.  Any partially constructed Tx
+     packet is left as is and can continue being filled afterwards.
+
+     It returns 0 if the call was requeued and an error otherwise.
+
 
 =======================
 CONFIGURABLE PARAMETERS