Keep the rxrpc_connection struct's idea of the service ID that is exposed
in the protocol separate from the service ID that's used as a lookup key.

This allows the protocol service ID on a client connection to get upgraded
without making the connection unfindable for other client calls that also
would like to use the upgraded connection.

The connection's actual service ID is then returned through recvmsg() by
way of msg_name.

Whilst we're at it, we get rid of the last_service_id field from each
channel.  The service ID is per-connection, not per-call and an entire
connection is upgraded in one go.

Signed-off-by: David Howells <dhowells@redhat.com>

Add a tracepoint (rxrpc_rx_proto) to record protocol errors in received
packets.  The following changes are made:

 (1) Add a function, __rxrpc_abort_eproto(), to note a protocol error on a
     call and mark the call aborted.  This is wrapped by
     rxrpc_abort_eproto() that makes the why string usable in trace.

 (2) Add trace_rxrpc_rx_proto() or rxrpc_abort_eproto() to protocol error
     generation points, replacing rxrpc_abort_call() with the latter.

 (3) Only send an abort packet in rxkad_verify_packet*() if we actually
     managed to abort the call.

Note that a trace event is also emitted if a kernel user (e.g. afs) tries
to send data through a call when it's not in the transmission phase, though
it's not technically a receive event.

Signed-off-by: David Howells <dhowells@redhat.com>

Use negative error codes in struct rxrpc_call::error because that's what
the kernel normally deals with and to make the code consistent.  We only
turn them positive when transcribing into a cmsg for userspace recvmsg.

Signed-off-by: David Howells <dhowells@redhat.com>

If we receive a BUSY packet for a call we think we've just completed, the
packet is handed off to the connection processor to deal with - but the
connection processor doesn't expect a BUSY packet and so flags a protocol
error.

Fix this by simply ignoring the BUSY packet for the moment.

The symptom of this may appear as a system call failing with EPROTO.  This
may be triggered by pressing ctrl-C under some circumstances.

This comes about we abort calls due to interruption by a signal (which we
shouldn't do, but that's going to be a large fix and mostly in fs/afs/).
What happens is that we abort the call and may also abort follow up calls
too (this needs offloading somehoe).  So we see a transmission of something
like the following sequence of packets:

	DATA for call N
	ABORT call N
	DATA for call N+1
	ABORT call N+1

in very quick succession on the same channel.  However, the peer may have
deferred the processing of the ABORT from the call N to a background thread
and thus sees the DATA message from the call N+1 coming in before it has
cleared the channel.  Thus it sends a BUSY packet[*].

[*] Note that some implementations (OpenAFS, for example) mark the BUSY
    packet with one plus the callNumber of the call prior to call N.
    Ordinarily, this would be call N, but there's no requirement for the
    calls on a channel to be numbered strictly sequentially (the number is
    required to increase).

    This is wrong and means that the callNumber in the BUSY packet should
    be ignored (it really ought to be N+1 since that's what it's in
    response to).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The offset field in struct rxrpc_skb_priv is unnecessary as the value can
always be calculated.

Signed-off-by: David Howells <dhowells@redhat.com>

Implement RxRPC slow-start, which is similar to RFC 5681 for TCP.  A
tracepoint is added to log the state of the congestion management algorithm
and the decisions it makes.

Notes:

 (1) Since we send fixed-size DATA packets (apart from the final packet in
     each phase), counters and calculations are in terms of packets rather
     than bytes.

 (2) The ACK packet carries the equivalent of TCP SACK.

 (3) The FLIGHT_SIZE calculation in RFC 5681 doesn't seem particularly
     suited to SACK of a small number of packets.  It seems that, almost
     inevitably, by the time three 'duplicate' ACKs have been seen, we have
     narrowed the loss down to one or two missing packets, and the
     FLIGHT_SIZE calculation ends up as 2.

 (4) In rxrpc_resend(), if there was no data that apparently needed
     retransmission, we transmit a PING ACK to ask the peer to tell us what
     its Rx window state is.

Signed-off-by: David Howells <dhowells@redhat.com>

Add a tracepoint to log transmission of DATA packets (including loss
injection).

Adjust the ACK transmission tracepoint to include the packet serial number
and to line this up with the DATA transmission display.

Signed-off-by: David Howells <dhowells@redhat.com>

Improve sk_buff tracing within AF_RXRPC by the following means:

 (1) Use an enum to note the event type rather than plain integers and use
     an array of event names rather than a big multi ?: list.

 (2) Distinguish Rx from Tx packets and account them separately.  This
     requires the call phase to be tracked so that we know what we might
     find in rxtx_buffer[].

 (3) Add a parameter to rxrpc_{new,see,get,free}_skb() to indicate the
     event type.

 (4) A pair of 'rotate' events are added to indicate packets that are about
     to be rotated out of the Rx and Tx windows.

 (5) A pair of 'lost' events are added, along with rxrpc_lose_skb() for
     packet loss injection recording.

Signed-off-by: David Howells <dhowells@redhat.com>
 

Add a tracepoint to log information about ACK transmission.

Signed-off-by: David Howels <dhowells@redhat.com>

Add a pair of tracepoints, one to track rxrpc_connection struct ref
counting and the other to track the client connection cache state.

Signed-off-by: David Howells <dhowells@redhat.com>