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, 97 insertions, 5 deletions

diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index d7809a0620b4..fcdd6555a820 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -269,11 +269,6 @@ struct rxrpc_call *rxrpc_new_client_call(struct rxrpc_sock *rx,
 	trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
 			 here, NULL);
 
-	spin_lock_bh(&call->conn->params.peer->lock);
-	hlist_add_head(&call->error_link,
-		       &call->conn->params.peer->error_targets);
-	spin_unlock_bh(&call->conn->params.peer->lock);
-
 	rxrpc_start_call_timer(call);
 
 	_net("CALL new %d on CONN %d", call->debug_id, call->conn->debug_id);
@@ -304,6 +299,48 @@ error:
 }
 
 /*
+ * Retry a call to a new address.  It is expected that the Tx queue of the call
+ * will contain data previously packaged for an old call.
+ */
+int rxrpc_retry_client_call(struct rxrpc_sock *rx,
+			    struct rxrpc_call *call,
+			    struct rxrpc_conn_parameters *cp,
+			    struct sockaddr_rxrpc *srx,
+			    gfp_t gfp)
+{
+	const void *here = __builtin_return_address(0);
+	int ret;
+
+	/* Set up or get a connection record and set the protocol parameters,
+	 * including channel number and call ID.
+	 */
+	ret = rxrpc_connect_call(call, cp, srx, gfp);
+	if (ret < 0)
+		goto error;
+
+	trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
+			 here, NULL);
+
+	rxrpc_start_call_timer(call);
+
+	_net("CALL new %d on CONN %d", call->debug_id, call->conn->debug_id);
+
+	if (!test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
+		rxrpc_queue_call(call);
+
+	_leave(" = 0");
+	return 0;
+
+error:
+	rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
+				  RX_CALL_DEAD, ret);
+	trace_rxrpc_call(call, rxrpc_call_error, atomic_read(&call->usage),
+			 here, ERR_PTR(ret));
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
  * Set up an incoming call.  call->conn points to the connection.
  * This is called in BH context and isn't allowed to fail.
  */
@@ -471,6 +508,61 @@ void rxrpc_release_call(struct rxrpc_sock *rx, struct rxrpc_call *call)
 }
 
 /*
+ * Prepare a kernel service call for retry.
+ */
+int rxrpc_prepare_call_for_retry(struct rxrpc_sock *rx, struct rxrpc_call *call)
+{
+	const void *here = __builtin_return_address(0);
+	int i;
+	u8 last = 0;
+
+	_enter("{%d,%d}", call->debug_id, atomic_read(&call->usage));
+
+	trace_rxrpc_call(call, rxrpc_call_release, atomic_read(&call->usage),
+			 here, (const void *)call->flags);
+
+	ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);
+	ASSERTCMP(call->completion, !=, RXRPC_CALL_REMOTELY_ABORTED);
+	ASSERTCMP(call->completion, !=, RXRPC_CALL_LOCALLY_ABORTED);
+	ASSERT(list_empty(&call->recvmsg_link));
+
+	del_timer_sync(&call->timer);
+
+	_debug("RELEASE CALL %p (%d CONN %p)", call, call->debug_id, call->conn);
+
+	if (call->conn)
+		rxrpc_disconnect_call(call);
+
+	if (rxrpc_is_service_call(call) ||
+	    !call->tx_phase ||
+	    call->tx_hard_ack != 0 ||
+	    call->rx_hard_ack != 0 ||
+	    call->rx_top != 0)
+		return -EINVAL;
+
+	call->state = RXRPC_CALL_UNINITIALISED;
+	call->completion = RXRPC_CALL_SUCCEEDED;
+	call->call_id = 0;
+	call->cid = 0;
+	call->cong_cwnd = 0;
+	call->cong_extra = 0;
+	call->cong_ssthresh = 0;
+	call->cong_mode = 0;
+	call->cong_dup_acks = 0;
+	call->cong_cumul_acks = 0;
+	call->acks_lowest_nak = 0;
+
+	for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++) {
+		last |= call->rxtx_annotations[i];
+		call->rxtx_annotations[i] &= RXRPC_TX_ANNO_LAST;
+		call->rxtx_annotations[i] |= RXRPC_TX_ANNO_RETRANS;
+	}
+
+	_leave(" = 0");
+	return 0;
+}
+
+/*
  * release all the calls associated with a socket
  */
 void rxrpc_release_calls_on_socket(struct rxrpc_sock *rx)