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authorDavid Howells <dhowells@redhat.com>2007-04-26 18:50:17 -0400
committerDavid S. Miller <davem@davemloft.net>2007-04-26 18:50:17 -0400
commit651350d10f93bed7003c9a66e24cf25e0f8eed3d (patch)
tree4748c1dd0b1a905b0e34b100c3c6ced6565a06de /Documentation/networking
parentec26815ad847dbf74a1e27aa5515fb7d5dc6ee6f (diff)
[AF_RXRPC]: Add an interface to the AF_RXRPC module for the AFS filesystem to use
Add an interface to the AF_RXRPC module so that the AFS filesystem module can more easily make use of the services available. AFS still opens a socket but then uses the action functions in lieu of sendmsg() and registers an intercept functions to grab messages before they're queued on the socket Rx queue. This permits AFS (or whatever) to: (1) Avoid the overhead of using the recvmsg() call. (2) Use different keys directly on individual client calls on one socket rather than having to open a whole slew of sockets, one for each key it might want to use. (3) Avoid calling request_key() at the point of issue of a call or opening of a socket. This is done instead by AFS at the point of open(), unlink() or other VFS operation and the key handed through. (4) Request the use of something other than GFP_KERNEL to allocate memory. Furthermore: (*) The socket buffer markings used by RxRPC are made available for AFS so that it can interpret the cooked RxRPC messages itself. (*) rxgen (un)marshalling abort codes are made available. The following documentation for the kernel interface is added to Documentation/networking/rxrpc.txt: ========================= AF_RXRPC KERNEL INTERFACE ========================= The AF_RXRPC module also provides an interface for use by in-kernel utilities such as the AFS filesystem. This permits such a utility to: (1) Use different keys directly on individual client calls on one socket rather than having to open a whole slew of sockets, one for each key it might want to use. (2) Avoid having RxRPC call request_key() at the point of issue of a call or opening of a socket. Instead the utility is responsible for requesting a key at the appropriate point. AFS, for instance, would do this during VFS operations such as open() or unlink(). The key is then handed through when the call is initiated. (3) Request the use of something other than GFP_KERNEL to allocate memory. (4) Avoid the overhead of using the recvmsg() call. RxRPC messages can be intercepted before they get put into the socket Rx queue and the socket buffers manipulated directly. To use the RxRPC facility, a kernel utility must still open an AF_RXRPC socket, bind an addess as appropriate and listen if it's to be a server socket, but then it passes this to the kernel interface functions. The kernel interface functions are as follows: (*) Begin a new client call. 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); This allocates the infrastructure to make a new RxRPC call and assigns call and connection numbers. The call will be made on the UDP port that the socket is bound to. The call will go to the destination address of a connected client socket unless an alternative is supplied (srx is non-NULL). If a key is supplied then this will be used to secure the call instead of the key bound to the socket with the RXRPC_SECURITY_KEY sockopt. Calls secured in this way will still share connections if at all possible. The user_call_ID is equivalent to that supplied to sendmsg() in the control data buffer. It is entirely feasible to use this to point to a kernel data structure. If this function is successful, an opaque reference to the RxRPC call is returned. The caller now holds a reference on this and it must be properly ended. (*) End a client call. void rxrpc_kernel_end_call(struct rxrpc_call *call); This is used to end a previously begun call. The user_call_ID is expunged from AF_RXRPC's knowledge and will not be seen again in association with the specified call. (*) Send data through a call. int rxrpc_kernel_send_data(struct rxrpc_call *call, struct msghdr *msg, size_t len); This is used to supply either the request part of a client call or the reply part of a server call. msg.msg_iovlen and msg.msg_iov specify the data buffers to be used. msg_iov may not be NULL and must point exclusively to in-kernel virtual addresses. msg.msg_flags may be given MSG_MORE if there will be subsequent data sends for this call. 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. (*) Abort a call. void rxrpc_kernel_abort_call(struct rxrpc_call *call, u32 abort_code); This is used to abort a call if it's still in an abortable state. The abort code specified will be placed in the ABORT message sent. (*) Intercept received RxRPC messages. typedef void (*rxrpc_interceptor_t)(struct sock *sk, unsigned long user_call_ID, struct sk_buff *skb); void rxrpc_kernel_intercept_rx_messages(struct socket *sock, rxrpc_interceptor_t interceptor); This installs an interceptor function on the specified AF_RXRPC socket. All messages that would otherwise wind up in the socket's Rx queue are then diverted to this function. Note that care must be taken to process the messages in the right order to maintain DATA message sequentiality. The interceptor function itself is provided with the address of the socket and handling the incoming message, the ID assigned by the kernel utility to the call and the socket buffer containing the message. The skb->mark field indicates the type of message: MARK MEANING =============================== ======================================= RXRPC_SKB_MARK_DATA Data message RXRPC_SKB_MARK_FINAL_ACK Final ACK received for an incoming call RXRPC_SKB_MARK_BUSY Client call rejected as server busy RXRPC_SKB_MARK_REMOTE_ABORT Call aborted by peer RXRPC_SKB_MARK_NET_ERROR Network error detected RXRPC_SKB_MARK_LOCAL_ERROR Local error encountered RXRPC_SKB_MARK_NEW_CALL New incoming call awaiting acceptance The remote abort message can be probed with rxrpc_kernel_get_abort_code(). The two error messages can be probed with rxrpc_kernel_get_error_number(). A new call can be accepted with rxrpc_kernel_accept_call(). Data messages can have their contents extracted with the usual bunch of socket buffer manipulation functions. A data message can be determined to be the last one in a sequence with rxrpc_kernel_is_data_last(). When a data message has been used up, rxrpc_kernel_data_delivered() should be called on it.. Non-data messages should be handled to rxrpc_kernel_free_skb() to dispose of. It is possible to get extra refs on all types of message for later freeing, but this may pin the state of a call until the message is finally freed. (*) Accept an incoming call. struct rxrpc_call * rxrpc_kernel_accept_call(struct socket *sock, unsigned long user_call_ID); This is used to accept an incoming call and to assign it a call ID. This function is similar to rxrpc_kernel_begin_call() and calls accepted must be ended in the same way. If this function is successful, an opaque reference to the RxRPC call is returned. The caller now holds a reference on this and it must be properly ended. (*) Reject an incoming call. int rxrpc_kernel_reject_call(struct socket *sock); This is used to reject the first incoming call on the socket's queue with a BUSY message. -ENODATA is returned if there were no incoming calls. Other errors may be returned if the call had been aborted (-ECONNABORTED) or had timed out (-ETIME). (*) Record the delivery of a data message and free it. void rxrpc_kernel_data_delivered(struct sk_buff *skb); This is used to record a data message as having been delivered and to update the ACK state for the call. The socket buffer will be freed. (*) 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. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/rxrpc.txt196
1 files changed, 196 insertions, 0 deletions
diff --git a/Documentation/networking/rxrpc.txt b/Documentation/networking/rxrpc.txt
index fb809b738a0d..cae231b1c134 100644
--- a/Documentation/networking/rxrpc.txt
+++ b/Documentation/networking/rxrpc.txt
@@ -25,6 +25,8 @@ Contents of this document:
25 25
26 (*) Example server usage. 26 (*) Example server usage.
27 27
28 (*) AF_RXRPC kernel interface.
29
28 30
29======== 31========
30OVERVIEW 32OVERVIEW
@@ -661,3 +663,197 @@ A server would be set up to accept operations in the following manner:
661Note that all the communications for a particular service take place through 663Note that all the communications for a particular service take place through
662the one server socket, using control messages on sendmsg() and recvmsg() to 664the one server socket, using control messages on sendmsg() and recvmsg() to
663determine the call affected. 665determine the call affected.
666
667
668=========================
669AF_RXRPC KERNEL INTERFACE
670=========================
671
672The AF_RXRPC module also provides an interface for use by in-kernel utilities
673such as the AFS filesystem. This permits such a utility to:
674
675 (1) Use different keys directly on individual client calls on one socket
676 rather than having to open a whole slew of sockets, one for each key it
677 might want to use.
678
679 (2) Avoid having RxRPC call request_key() at the point of issue of a call or
680 opening of a socket. Instead the utility is responsible for requesting a
681 key at the appropriate point. AFS, for instance, would do this during VFS
682 operations such as open() or unlink(). The key is then handed through
683 when the call is initiated.
684
685 (3) Request the use of something other than GFP_KERNEL to allocate memory.
686
687 (4) Avoid the overhead of using the recvmsg() call. RxRPC messages can be
688 intercepted before they get put into the socket Rx queue and the socket
689 buffers manipulated directly.
690
691To use the RxRPC facility, a kernel utility must still open an AF_RXRPC socket,
692bind an addess as appropriate and listen if it's to be a server socket, but
693then it passes this to the kernel interface functions.
694
695The kernel interface functions are as follows:
696
697 (*) Begin a new client call.
698
699 struct rxrpc_call *
700 rxrpc_kernel_begin_call(struct socket *sock,
701 struct sockaddr_rxrpc *srx,
702 struct key *key,
703 unsigned long user_call_ID,
704 gfp_t gfp);
705
706 This allocates the infrastructure to make a new RxRPC call and assigns
707 call and connection numbers. The call will be made on the UDP port that
708 the socket is bound to. The call will go to the destination address of a
709 connected client socket unless an alternative is supplied (srx is
710 non-NULL).
711
712 If a key is supplied then this will be used to secure the call instead of
713 the key bound to the socket with the RXRPC_SECURITY_KEY sockopt. Calls
714 secured in this way will still share connections if at all possible.
715
716 The user_call_ID is equivalent to that supplied to sendmsg() in the
717 control data buffer. It is entirely feasible to use this to point to a
718 kernel data structure.
719
720 If this function is successful, an opaque reference to the RxRPC call is
721 returned. The caller now holds a reference on this and it must be
722 properly ended.
723
724 (*) End a client call.
725
726 void rxrpc_kernel_end_call(struct rxrpc_call *call);
727
728 This is used to end a previously begun call. The user_call_ID is expunged
729 from AF_RXRPC's knowledge and will not be seen again in association with
730 the specified call.
731
732 (*) Send data through a call.
733
734 int rxrpc_kernel_send_data(struct rxrpc_call *call, struct msghdr *msg,
735 size_t len);
736
737 This is used to supply either the request part of a client call or the
738 reply part of a server call. msg.msg_iovlen and msg.msg_iov specify the
739 data buffers to be used. msg_iov may not be NULL and must point
740 exclusively to in-kernel virtual addresses. msg.msg_flags may be given
741 MSG_MORE if there will be subsequent data sends for this call.
742
743 The msg must not specify a destination address, control data or any flags
744 other than MSG_MORE. len is the total amount of data to transmit.
745
746 (*) Abort a call.
747
748 void rxrpc_kernel_abort_call(struct rxrpc_call *call, u32 abort_code);
749
750 This is used to abort a call if it's still in an abortable state. The
751 abort code specified will be placed in the ABORT message sent.
752
753 (*) Intercept received RxRPC messages.
754
755 typedef void (*rxrpc_interceptor_t)(struct sock *sk,
756 unsigned long user_call_ID,
757 struct sk_buff *skb);
758
759 void
760 rxrpc_kernel_intercept_rx_messages(struct socket *sock,
761 rxrpc_interceptor_t interceptor);
762
763 This installs an interceptor function on the specified AF_RXRPC socket.
764 All messages that would otherwise wind up in the socket's Rx queue are
765 then diverted to this function. Note that care must be taken to process
766 the messages in the right order to maintain DATA message sequentiality.
767
768 The interceptor function itself is provided with the address of the socket
769 and handling the incoming message, the ID assigned by the kernel utility
770 to the call and the socket buffer containing the message.
771
772 The skb->mark field indicates the type of message:
773
774 MARK MEANING
775 =============================== =======================================
776 RXRPC_SKB_MARK_DATA Data message
777 RXRPC_SKB_MARK_FINAL_ACK Final ACK received for an incoming call
778 RXRPC_SKB_MARK_BUSY Client call rejected as server busy
779 RXRPC_SKB_MARK_REMOTE_ABORT Call aborted by peer
780 RXRPC_SKB_MARK_NET_ERROR Network error detected
781 RXRPC_SKB_MARK_LOCAL_ERROR Local error encountered
782 RXRPC_SKB_MARK_NEW_CALL New incoming call awaiting acceptance
783
784 The remote abort message can be probed with rxrpc_kernel_get_abort_code().
785 The two error messages can be probed with rxrpc_kernel_get_error_number().
786 A new call can be accepted with rxrpc_kernel_accept_call().
787
788 Data messages can have their contents extracted with the usual bunch of
789 socket buffer manipulation functions. A data message can be determined to
790 be the last one in a sequence with rxrpc_kernel_is_data_last(). When a
791 data message has been used up, rxrpc_kernel_data_delivered() should be
792 called on it..
793
794 Non-data messages should be handled to rxrpc_kernel_free_skb() to dispose
795 of. It is possible to get extra refs on all types of message for later
796 freeing, but this may pin the state of a call until the message is finally
797 freed.
798
799 (*) Accept an incoming call.
800
801 struct rxrpc_call *
802 rxrpc_kernel_accept_call(struct socket *sock,
803 unsigned long user_call_ID);
804
805 This is used to accept an incoming call and to assign it a call ID. This
806 function is similar to rxrpc_kernel_begin_call() and calls accepted must
807 be ended in the same way.
808
809 If this function is successful, an opaque reference to the RxRPC call is
810 returned. The caller now holds a reference on this and it must be
811 properly ended.
812
813 (*) Reject an incoming call.
814
815 int rxrpc_kernel_reject_call(struct socket *sock);
816
817 This is used to reject the first incoming call on the socket's queue with
818 a BUSY message. -ENODATA is returned if there were no incoming calls.
819 Other errors may be returned if the call had been aborted (-ECONNABORTED)
820 or had timed out (-ETIME).
821
822 (*) Record the delivery of a data message and free it.
823
824 void rxrpc_kernel_data_delivered(struct sk_buff *skb);
825
826 This is used to record a data message as having been delivered and to
827 update the ACK state for the call. The socket buffer will be freed.
828
829 (*) Free a message.
830
831 void rxrpc_kernel_free_skb(struct sk_buff *skb);
832
833 This is used to free a non-DATA socket buffer intercepted from an AF_RXRPC
834 socket.
835
836 (*) Determine if a data message is the last one on a call.
837
838 bool rxrpc_kernel_is_data_last(struct sk_buff *skb);
839
840 This is used to determine if a socket buffer holds the last data message
841 to be received for a call (true will be returned if it does, false
842 if not).
843
844 The data message will be part of the reply on a client call and the
845 request on an incoming call. In the latter case there will be more
846 messages, but in the former case there will not.
847
848 (*) Get the abort code from an abort message.
849
850 u32 rxrpc_kernel_get_abort_code(struct sk_buff *skb);
851
852 This is used to extract the abort code from a remote abort message.
853
854 (*) Get the error number from a local or network error message.
855
856 int rxrpc_kernel_get_error_number(struct sk_buff *skb);
857
858 This is used to extract the error number from a message indicating either
859 a local error occurred or a network error occurred.