rxrpc: Don't expose skbs to in-kernel users [ver #2]
Don't expose skbs to in-kernel users, such as the AFS filesystem, but
instead provide a notification hook the indicates that a call needs
attention and another that indicates that there's a new call to be
collected.
This makes the following possibilities more achievable:
(1) Call refcounting can be made simpler if skbs don't hold refs to calls.
(2) skbs referring to non-data events will be able to be freed much sooner
rather than being queued for AFS to pick up as rxrpc_kernel_recv_data
will be able to consult the call state.
(3) We can shortcut the receive phase when a call is remotely aborted
because we don't have to go through all the packets to get to the one
cancelling the operation.
(4) It makes it easier to do encryption/decryption directly between AFS's
buffers and sk_buffs.
(5) Encryption/decryption can more easily be done in the AFS's thread
contexts - usually that of the userspace process that issued a syscall
- rather than in one of rxrpc's background threads on a workqueue.
(6) AFS will be able to wait synchronously on a call inside AF_RXRPC.
To make this work, the following interface function has been added:
int rxrpc_kernel_recv_data(
struct socket *sock, struct rxrpc_call *call,
void *buffer, size_t bufsize, size_t *_offset,
bool want_more, u32 *_abort_code);
This is the recvmsg equivalent. It allows the caller to find out about the
state of a specific call and to transfer received data into a buffer
piecemeal.
afs_extract_data() and rxrpc_kernel_recv_data() now do all the extraction
logic between them. They don't wait synchronously yet because the socket
lock needs to be dealt with.
Five interface functions have been removed:
rxrpc_kernel_is_data_last()
rxrpc_kernel_get_abort_code()
rxrpc_kernel_get_error_number()
rxrpc_kernel_free_skb()
rxrpc_kernel_data_consumed()
As a temporary hack, sk_buffs going to an in-kernel call are queued on the
rxrpc_call struct (->knlrecv_queue) rather than being handed over to the
in-kernel user. To process the queue internally, a temporary function,
temp_deliver_data() has been added. This will be replaced with common code
between the rxrpc_recvmsg() path and the kernel_rxrpc_recv_data() path in a
future patch.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Documentation/networking/rxrpc.txt b/Documentation/networking/rxrpc.txt
index cfc8cb9..1b63bbc 100644
--- a/Documentation/networking/rxrpc.txt
+++ b/Documentation/networking/rxrpc.txt
@@ -748,6 +748,37 @@
The msg must not specify a destination address, control data or any flags
other than MSG_MORE. len is the total amount of data to transmit.
+ (*) Receive data from a call.
+
+ int rxrpc_kernel_recv_data(struct socket *sock,
+ struct rxrpc_call *call,
+ void *buf,
+ size_t size,
+ size_t *_offset,
+ bool want_more,
+ u32 *_abort)
+
+ This is used to receive data from either the reply part of a client call
+ or the request part of a service call. buf and size specify how much
+ data is desired and where to store it. *_offset is added on to buf and
+ subtracted from size internally; the amount copied into the buffer is
+ added to *_offset before returning.
+
+ want_more should be true if further data will be required after this is
+ satisfied and false if this is the last item of the receive phase.
+
+ There are three normal returns: 0 if the buffer was filled and want_more
+ was true; 1 if the buffer was filled, the last DATA packet has been
+ emptied and want_more was false; and -EAGAIN if the function needs to be
+ called again.
+
+ If the last DATA packet is processed but the buffer contains less than
+ the amount requested, EBADMSG is returned. If want_more wasn't set, but
+ more data was available, EMSGSIZE is returned.
+
+ If a remote ABORT is detected, the abort code received will be stored in
+ *_abort and ECONNABORTED will be returned.
+
(*) Abort a call.
void rxrpc_kernel_abort_call(struct socket *sock,
@@ -825,47 +856,6 @@
Other errors may be returned if the call had been aborted (-ECONNABORTED)
or had timed out (-ETIME).
- (*) Record the delivery of a data message.
-
- void rxrpc_kernel_data_consumed(struct rxrpc_call *call,
- struct sk_buff *skb);
-
- This is used to record a data message as having been consumed and to
- update the ACK state for the call. The message must still be passed to
- rxrpc_kernel_free_skb() for disposal by the caller.
-
- (*) Free a message.
-
- void rxrpc_kernel_free_skb(struct sk_buff *skb);
-
- This is used to free a non-DATA socket buffer intercepted from an AF_RXRPC
- socket.
-
- (*) Determine if a data message is the last one on a call.
-
- bool rxrpc_kernel_is_data_last(struct sk_buff *skb);
-
- This is used to determine if a socket buffer holds the last data message
- to be received for a call (true will be returned if it does, false
- if not).
-
- The data message will be part of the reply on a client call and the
- request on an incoming call. In the latter case there will be more
- messages, but in the former case there will not.
-
- (*) Get the abort code from an abort message.
-
- u32 rxrpc_kernel_get_abort_code(struct sk_buff *skb);
-
- This is used to extract the abort code from a remote abort message.
-
- (*) Get the error number from a local or network error message.
-
- int rxrpc_kernel_get_error_number(struct sk_buff *skb);
-
- This is used to extract the error number from a message indicating either
- a local error occurred or a network error occurred.
-
(*) Allocate a null key for doing anonymous security.
struct key *rxrpc_get_null_key(const char *keyname);