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rxrpc: Don't expose skbs to in-kernel users [ver #2]

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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>
This commit is contained in:
David Howells
2016-08-30 20:42:14 +01:00
committed by David S. Miller
parent 95ac399451
commit d001648ec7
16 changed files with 566 additions and 587 deletions
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29
net/rxrpc/af_rxrpc.c
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@@ -231,6 +231,8 @@ static int rxrpc_listen(struct socket *sock, int backlog)
* @srx: The address of the peer to contact
* @key: The security context to use (defaults to socket setting)
* @user_call_ID: The ID to use
* @gfp: The allocation constraints
* @notify_rx: Where to send notifications instead of socket queue
*
* Allow a kernel service to begin a call on the nominated socket. This just
* sets up all the internal tracking structures and allocates connection and
@@ -243,7 +245,8 @@ struct rxrpc_call *rxrpc_kernel_begin_call(struct socket *sock,
struct sockaddr_rxrpc *srx,
struct key *key,
unsigned long user_call_ID,
gfp_t gfp)
gfp_t gfp,
rxrpc_notify_rx_t notify_rx)
{
struct rxrpc_conn_parameters cp;
struct rxrpc_call *call;
@@ -270,6 +273,8 @@ struct rxrpc_call *rxrpc_kernel_begin_call(struct socket *sock,
cp.exclusive = false;
cp.service_id = srx->srx_service;
call = rxrpc_new_client_call(rx, &cp, srx, user_call_ID, gfp);
if (!IS_ERR(call))
call->notify_rx = notify_rx;
release_sock(&rx->sk);
_leave(" = %p", call);
@@ -289,31 +294,27 @@ void rxrpc_kernel_end_call(struct socket *sock, struct rxrpc_call *call)
{
_enter("%d{%d}", call->debug_id, atomic_read(&call->usage));
rxrpc_remove_user_ID(rxrpc_sk(sock->sk), call);
rxrpc_purge_queue(&call->knlrecv_queue);
rxrpc_put_call(call);
}
EXPORT_SYMBOL(rxrpc_kernel_end_call);
/**
* rxrpc_kernel_intercept_rx_messages - Intercept received RxRPC messages
* rxrpc_kernel_new_call_notification - Get notifications of new calls
* @sock: The socket to intercept received messages on
* @interceptor: The function to pass the messages to
* @notify_new_call: Function to be called when new calls appear
*
* Allow a kernel service to intercept messages heading for the Rx queue on an
* RxRPC socket. They get passed to the specified function instead.
* @interceptor should free the socket buffers it is given. @interceptor is
* called with the socket receive queue spinlock held and softirqs disabled -
* this ensures that the messages will be delivered in the right order.
* Allow a kernel service to be given notifications about new calls.
*/
void rxrpc_kernel_intercept_rx_messages(struct socket *sock,
rxrpc_interceptor_t interceptor)
void rxrpc_kernel_new_call_notification(
struct socket *sock,
rxrpc_notify_new_call_t notify_new_call)
{
struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
_enter("");
rx->interceptor = interceptor;
rx->notify_new_call = notify_new_call;
}
EXPORT_SYMBOL(rxrpc_kernel_intercept_rx_messages);
EXPORT_SYMBOL(rxrpc_kernel_new_call_notification);
/*
* connect an RxRPC socket