Cache the congestion window setting that was determined during a call's
transmission phase when it finishes so that it can be used by the next call
to the same peer, thereby shortcutting the slow-start algorithm.
The value is stored in the rxrpc_peer struct and is accessed without
locking. Each call takes the value that happens to be there when it starts
and just overwrites the value when it finishes.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Provide a control message that can be specified on the first sendmsg() of a
client call or the first sendmsg() of a service response to indicate the
total length of the data to be transmitted for that call.
Currently, because the length of the payload of an encrypted DATA packet is
encrypted in front of the data, the packet cannot be encrypted until we
know how much data it will hold.
By specifying the length at the beginning of the transmit phase, each DATA
packet length can be set before we start loading data from userspace (where
several sendmsg() calls may contribute to a particular packet).
An error will be returned if too little or too much data is presented in
the Tx phase.
Signed-off-by: David Howells <dhowells@redhat.com>
Make it possible for a client to use AuriStor's service upgrade facility.
The client does this by adding an RXRPC_UPGRADE_SERVICE control message to
the first sendmsg() of a call. This takes no parameters.
When recvmsg() starts returning data from the call, the service ID field in
the returned msg_name will reflect the result of the upgrade attempt. If
the upgrade was ignored, srx_service will match what was set in the
sendmsg(); if the upgrade happened the srx_service will be altered to
indicate the service the server upgraded to.
Note that:
(1) The choice of upgrade service is up to the server
(2) Further client calls to the same server that would share a connection
are blocked if an upgrade probe is in progress.
(3) This should only be used to probe the service. Clients should then
use the returned service ID in all subsequent communications with that
server (and not set the upgrade). Note that the kernel will not
retain this information should the connection expire from its cache.
(4) If a server that supports upgrading is replaced by one that doesn't,
whilst a connection is live, and if the replacement is running, say,
OpenAFS 1.6.4 or older or an older IBM AFS, then the replacement
server will not respond to packets sent to the upgraded connection.
At this point, calls will time out and the server must be reprobed.
Signed-off-by: David Howells <dhowells@redhat.com>
Implement AuriStor's service upgrade facility. There are three problems
that this is meant to deal with:
(1) Various of the standard AFS RPC calls have IPv4 addresses in their
requests and/or replies - but there's no room for including IPv6
addresses.
(2) Definition of IPv6-specific RPC operations in the standard operation
sets has not yet been achieved.
(3) One could envision the creation a new service on the same port that as
the original service. The new service could implement improved
operations - and the client could try this first, falling back to the
original service if it's not there.
Unfortunately, certain servers ignore packets addressed to a service
they don't implement and don't respond in any way - not even with an
ABORT. This means that the client must then wait for the call timeout
to occur.
What service upgrade does is to see if the connection is marked as being
'upgradeable' and if so, change the service ID in the server and thus the
request and reply formats. Note that the upgrade isn't mandatory - a
server that supports only the original call set will ignore the upgrade
request.
In the protocol, the procedure is then as follows:
(1) To request an upgrade, the first DATA packet in a new connection must
have the userStatus set to 1 (this is normally 0). The userStatus
value is normally ignored by the server.
(2) If the server doesn't support upgrading, the reply packets will
contain the same service ID as for the first request packet.
(3) If the server does support upgrading, all future reply packets on that
connection will contain the new service ID and the new service ID will
be applied to *all* further calls on that connection as well.
(4) The RPC op used to probe the upgrade must take the same request data
as the shadow call in the upgrade set (but may return a different
reply). GetCapability RPC ops were added to all standard sets for
just this purpose. Ops where the request formats differ cannot be
used for probing.
(5) The client must wait for completion of the probe before sending any
further RPC ops to the same destination. It should then use the
service ID that recvmsg() reported back in all future calls.
(6) The shadow service must have call definitions for all the operation
IDs defined by the original service.
To support service upgrading, a server should:
(1) Call bind() twice on its AF_RXRPC socket before calling listen().
Each bind() should supply a different service ID, but the transport
addresses must be the same. This allows the server to receive
requests with either service ID.
(2) Enable automatic upgrading by calling setsockopt(), specifying
RXRPC_UPGRADEABLE_SERVICE and passing in a two-member array of
unsigned shorts as the argument:
unsigned short optval[2];
This specifies a pair of service IDs. They must be different and must
match the service IDs bound to the socket. Member 0 is the service ID
to upgrade from and member 1 is the service ID to upgrade to.
Signed-off-by: David Howells <dhowells@redhat.com>
Permit bind() to be called on an AF_RXRPC socket more than once (currently
maximum twice) to bind multiple listening services to it. There are some
restrictions:
(1) All bind() calls involved must have a non-zero service ID.
(2) The service IDs must all be different.
(3) The rest of the address (notably the transport part) must be the same
in all (a single UDP socket is shared).
(4) This must be done before listen() or sendmsg() is called.
This allows someone to connect to the service socket with different service
IDs and lays the foundation for service upgrading.
The service ID used by an incoming call can be extracted from the msg_name
returned by recvmsg().
Signed-off-by: David Howells <dhowells@redhat.com>
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>
Support network namespacing in AF_RXRPC with the following changes:
(1) All the local endpoint, peer and call lists, locks, counters, etc. are
moved into the per-namespace record.
(2) All the connection tracking is moved into the per-namespace record
with the exception of the client connection ID tree, which is kept
global so that connection IDs are kept unique per-machine.
(3) Each namespace gets its own epoch. This allows each network namespace
to pretend to be a separate client machine.
(4) The /proc/net/rxrpc_xxx files are now called /proc/net/rxrpc/xxx and
the contents reflect the namespace.
fs/afs/ should be okay with this patch as it explicitly requires the current
net namespace to be init_net to permit a mount to proceed at the moment. It
will, however, need updating so that cells, IP addresses and DNS records are
per-namespace also.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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>
All the routines by which rxrpc is accessed from the outside are serialised
by means of the socket lock (sendmsg, recvmsg, bind,
rxrpc_kernel_begin_call(), ...) and this presents a problem:
(1) If a number of calls on the same socket are in the process of
connection to the same peer, a maximum of four concurrent live calls
are permitted before further calls need to wait for a slot.
(2) If a call is waiting for a slot, it is deep inside sendmsg() or
rxrpc_kernel_begin_call() and the entry function is holding the socket
lock.
(3) sendmsg() and recvmsg() or the in-kernel equivalents are prevented
from servicing the other calls as they need to take the socket lock to
do so.
(4) The socket is stuck until a call is aborted and makes its slot
available to the waiter.
Fix this by:
(1) Provide each call with a mutex ('user_mutex') that arbitrates access
by the users of rxrpc separately for each specific call.
(2) Make rxrpc_sendmsg() and rxrpc_recvmsg() unlock the socket as soon as
they've got a call and taken its mutex.
Note that I'm returning EWOULDBLOCK from recvmsg() if MSG_DONTWAIT is
set but someone else has the lock. Should I instead only return
EWOULDBLOCK if there's nothing currently to be done on a socket, and
sleep in this particular instance because there is something to be
done, but we appear to be blocked by the interrupt handler doing its
ping?
(3) Make rxrpc_new_client_call() unlock the socket after allocating a new
call, locking its user mutex and adding it to the socket's call tree.
The call is returned locked so that sendmsg() can add data to it
immediately.
From the moment the call is in the socket tree, it is subject to
access by sendmsg() and recvmsg() - even if it isn't connected yet.
(4) Lock new service calls in the UDP data_ready handler (in
rxrpc_new_incoming_call()) because they may already be in the socket's
tree and the data_ready handler makes them live immediately if a user
ID has already been preassigned.
Note that the new call is locked before any notifications are sent
that it is live, so doing mutex_trylock() *ought* to always succeed.
Userspace is prevented from doing sendmsg() on calls that are in a
too-early state in rxrpc_do_sendmsg().
(5) Make rxrpc_new_incoming_call() return the call with the user mutex
held so that a ping can be scheduled immediately under it.
Note that it might be worth moving the ping call into
rxrpc_new_incoming_call() and then we can drop the mutex there.
(6) Make rxrpc_accept_call() take the lock on the call it is accepting and
release the socket after adding the call to the socket's tree. This
is slightly tricky as we've dequeued the call by that point and have
to requeue it.
Note that requeuing emits a trace event.
(7) Make rxrpc_kernel_send_data() and rxrpc_kernel_recv_data() take the
new mutex immediately and don't bother with the socket mutex at all.
This patch has the nice bonus that calls on the same socket are now to some
extent parallelisable.
Note that we might want to move rxrpc_service_prealloc() calls out from the
socket lock and give it its own lock, so that we don't hang progress in
other calls because we're waiting for the allocator.
We probably also want to avoid calling rxrpc_notify_socket() from within
the socket lock (rxrpc_accept_call()).
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marc Dionne <marc.c.dionne@auristor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Allow listen() with a backlog of 0 to be used to disable listening on an
AF_RXRPC socket. This also releases any preallocation, thereby making it
easier for a kernel service to account for all allocated call structures
when shutting down the service.
The socket cannot thereafter have listening reenabled, but must rather be
closed and reopened.
Signed-off-by: David Howells <dhowells@redhat.com>
Fix the way enum values are translated into strings in AF_RXRPC
tracepoints. The problem with just doing a lookup in a normal flat array
of strings or chars is that external tracing infrastructure can't find it.
Rather, TRACE_DEFINE_ENUM must be used.
Also sort the enums and string tables to make it easier to keep them in
order so that a future patch to __print_symbolic() can be optimised to try
a direct lookup into the table first before iterating over it.
A couple of _proto() macro calls are removed because they refered to tables
that got moved to the tracing infrastructure. The relevant data can be
found by way of tracing.
Signed-off-by: David Howells <dhowells@redhat.com>
We need to generate a DELAY ACK from the service end of an operation if we
start doing the actual operation work and it takes longer than expected.
This will hard-ACK the request data and allow the client to release its
resources.
To make this work:
(1) We have to set the ack timer and propose an ACK when the call moves to
the RXRPC_CALL_SERVER_ACK_REQUEST and clear the pending ACK and cancel
the timer when we start transmitting the reply (the first DATA packet
of the reply implicitly ACKs the request phase).
(2) It must be possible to set the timer when the caller is holding
call->state_lock, so split the lock-getting part of the timer function
out.
(3) Add trace notes for the ACK we're requesting and the timer we clear.
Signed-off-by: David Howells <dhowells@redhat.com>
Separate the output of PING ACKs from the output of other sorts of ACK so
that if we receive a PING ACK and schedule transmission of a PING RESPONSE
ACK, the response doesn't get cancelled by a PING ACK we happen to be
scheduling transmission of at the same time.
If a PING RESPONSE gets lost, the other side might just sit there waiting
for it and refuse to proceed otherwise.
Signed-off-by: David Howells <dhowells@redhat.com>
Split rxrpc_send_data_packet() to separate ACK generation (which is more
complicated) from ABORT generation. This simplifies the code a bit and
fixes the following warning:
In file included from ../net/rxrpc/output.c:20:0:
net/rxrpc/output.c: In function 'rxrpc_send_call_packet':
net/rxrpc/ar-internal.h:1187:27: error: 'top' may be used uninitialized in this function [-Werror=maybe-uninitialized]
net/rxrpc/output.c:103:24: note: 'top' was declared here
net/rxrpc/output.c:225:25: error: 'hard_ack' may be used uninitialized in this function [-Werror=maybe-uninitialized]
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Keep that call timeouts as ktimes rather than jiffies so that they can be
expressed as functions of RTT.
Signed-off-by: David Howells <dhowells@redhat.com>
Reduce the rxrpc_local::services list to just a pointer as we don't permit
multiple service endpoints to bind to a single transport endpoints (this is
excluded by rxrpc_lookup_local()).
The reason we don't allow this is that if you send a request to an AFS
filesystem service, it will try to talk back to your cache manager on the
port you sent from (this is how file change notifications are handled). To
prevent someone from stealing your CM callbacks, we don't let AF_RXRPC
sockets share a UDP socket if at least one of them has a service bound.
Signed-off-by: David Howells <dhowells@redhat.com>
In rxrpc_send_data_packet() make the loss-injection path return through the
same code as the transmission path so that the RTT determination is
initiated and any future timer shuffling will be done, despite the packet
having been binned.
Whilst we're at it:
(1) Add to the tx_data tracepoint an indication of whether or not we're
retransmitting a data packet.
(2) When we're deciding whether or not to request an ACK, rather than
checking if we're in fast-retransmit mode check instead if we're
retransmitting.
(3) Don't invoke the lose_skb tracepoint when losing a Tx packet as we're
not altering the sk_buff refcount nor are we just seeing it after
getting it off the Tx list.
(4) The rxrpc_skb_tx_lost note is then no longer used so remove it.
(5) rxrpc_lose_skb() no longer needs to deal with rxrpc_skb_tx_lost.
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>
If we've sent all the request data in a client call but haven't seen any
sign of the reply data yet, schedule an ACK to be sent to the server to
find out if the reply data got lost.
If the server hasn't yet hard-ACK'd the request data, we send a PING ACK to
demand a response to find out whether we need to retransmit.
If the server says it has received all of the data, we send an IDLE ACK to
tell the server that we haven't received anything in the receive phase as
yet.
To make this work, a non-immediate PING ACK must carry a delay. I've chosen
the same as the IDLE ACK for the moment.
Signed-off-by: David Howells <dhowells@redhat.com>
Generate a summary of the Tx buffer packet state when an ACK is received
for use in a later patch that does congestion management.
Signed-off-by: David Howells <dhowells@redhat.com>
Clear the ACK reason, ACK timer and resend timer when entering the client
reply phase when the first DATA packet is received. New ACKs will be
proposed once the data is queued.
The resend timer is no longer relevant and we need to cancel ACKs scheduled
to probe for a lost reply.
Signed-off-by: David Howells <dhowells@redhat.com>
Send an ACK if we haven't sent one for the last two packets we've received.
This keeps the other end apprised of where we've got to - which is
important if they're doing slow-start.
We do this in recvmsg so that we can dispatch a packet directly without the
need to wake up the background thread.
This should possibly be made configurable in future.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a tracepoint to log proposed ACKs, including whether the proposal is
used to update a pending ACK or is discarded in favour of an easlier,
higher priority ACK.
Whilst we're at it, get rid of the rxrpc_acks() function and access the
name array directly. We do, however, need to validate the ACK reason
number given to trace_rxrpc_rx_ack() to make sure we don't overrun the
array.
Signed-off-by: David Howells <dhowells@redhat.com>
When the last packet of data to be transmitted on a call is queued, tx_top
is set and then the RXRPC_CALL_TX_LAST flag is set. Unfortunately, this
leaves a race in the ACK processing side of things because the flag affects
the interpretation of tx_top and also allows us to start receiving reply
data before we've finished transmitting.
To fix this, make the following changes:
(1) rxrpc_queue_packet() now sets a marker in the annotation buffer
instead of setting the RXRPC_CALL_TX_LAST flag.
(2) rxrpc_rotate_tx_window() detects the marker and sets the flag in the
same context as the routines that use it.
(3) rxrpc_end_tx_phase() is simplified to just shift the call state.
The Tx window must have been rotated before calling to discard the
last packet.
(4) rxrpc_receiving_reply() is added to handle the arrival of the first
DATA packet of a reply to a client call (which is an implicit ACK of
the Tx phase).
(5) The last part of rxrpc_input_ack() is reordered to perform Tx
rotation, then soft-ACK application and then to end the phase if we've
rotated the last packet. In the event of a terminal ACK, the soft-ACK
application will be skipped as nAcks should be 0.
(6) rxrpc_input_ackall() now has to rotate as well as ending the phase.
In addition:
(7) Alter the transmit tracepoint to log the rotation of the last packet.
(8) Remove the no-longer relevant queue_reqack tracepoint note. The
ACK-REQUESTED packet header flag is now set as needed when we actually
transmit the packet and may vary by retransmission.
Signed-off-by: David Howells <dhowells@redhat.com>
When a DATA packet has its initial transmission, we may need to start or
adjust the resend timer. Without this we end up relying on being sent a
NACK to initiate the resend.
Signed-off-by: David Howells <dhowells@redhat.com>
Reduce the number of ACK-Requests we set on DATA packets that we're sending
to reduce network traffic. We set the flag on odd-numbered DATA packets to
start off the RTT cache until we have at least three entries in it and then
probe once per second thereafter to keep it topped up.
This could be made tunable in future.
Note that from this point, the RXRPC_REQUEST_ACK flag is set on DATA
packets as we transmit them and not stored statically in the sk_buff.
Signed-off-by: David Howells <dhowells@redhat.com>
In addition to sending a PING ACK to gain RTT data, we can set the
RXRPC_REQUEST_ACK flag on a DATA packet and get a REQUESTED-ACK ACK. The
ACK packet contains the serial number of the packet it is in response to,
so we can look through the Tx buffer for a matching DATA packet.
This requires that the data packets be stamped with the time of
transmission as a ktime rather than having the resend_at time in jiffies.
This further requires the resend code to do the resend determination in
ktimes and convert to jiffies to set the timer.
Signed-off-by: David Howells <dhowells@redhat.com>
Send a PING ACK packet to the peer when we get a new incoming call from a
peer we don't have a record for. The PING RESPONSE ACK packet will tell us
the following about the peer:
(1) its receive window size
(2) its MTU sizes
(3) its support for jumbo DATA packets
(4) if it supports slow start (similar to RFC 5681)
(5) an estimate of the RTT
This is necessary because the peer won't normally send us an ACK until it
gets to the Rx phase and we send it a packet, but we would like to know
some of this information before we start sending packets.
A pair of tracepoints are added so that RTT determination can be observed.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a function to track the average RTT for a peer. Sources of RTT data
will be added in subsequent patches.
The RTT data will be useful in the future for determining resend timeouts
and for handling the slow-start part of the Rx protocol.
Also add a pair of tracepoints, one to log transmissions to elicit a
response for RTT purposes and one to log responses that contribute RTT
data.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a Tx-phase annotation for packet buffers to indicate that a buffer has
already been retransmitted. This will be used by future congestion
management. Re-retransmissions of a packet don't affect the congestion
window managment in the same way as initial retransmissions.
Signed-off-by: David Howells <dhowells@redhat.com>
Don't store the rxrpc protocol header in sk_buffs on the transmit queue,
but rather generate it on the fly and pass it to kernel_sendmsg() as a
separate iov. This reduces the amount of storage required.
Note that the security header is still stored in the sk_buff as it may get
encrypted along with the data (and doesn't change with each transmission).
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 follow the insertion of a packet into the transmit
buffer, its transmission and its rotation out of the buffer.
Signed-off-by: David Howells <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>
Add additional call tracepoint points for noting call-connected,
call-released and connection-failed events.
Also fix one tracepoint that was using an integer instead of the
corresponding enum value as the point type.
Signed-off-by: David Howells <dhowells@redhat.com>
Print a symbolic packet type name for each valid received packet in the
trace output, not just a number.
Signed-off-by: David Howells <dhowells@redhat.com>
call->rx_winsize should be initialised to the sysctl setting and the sysctl
setting should be limited to the maximum we want to permit. Further, we
need to place this in the ACK info instead of the sysctl setting.
Furthermore, discard the idea of accepting the subpackets of a jumbo packet
that lie beyond the receive window when the first packet of the jumbo is
within the window. Just discard the excess subpackets instead. This
allows the receive window to be opened up right to the buffer size less one
for the dead slot.
Signed-off-by: David Howells <dhowells@redhat.com>
Adjust the call ref tracepoint to show references held on a call by the
kernel API separately as much as possible and add an additional trace to at
the allocation point from the preallocation buffer for an incoming call.
Note that this doesn't show the allocation of a client call for the kernel
separately at the moment.
Signed-off-by: David Howells <dhowells@redhat.com>
Rewrite the data and ack handling code such that:
(1) Parsing of received ACK and ABORT packets and the distribution and the
filing of DATA packets happens entirely within the data_ready context
called from the UDP socket. This allows us to process and discard ACK
and ABORT packets much more quickly (they're no longer stashed on a
queue for a background thread to process).
(2) We avoid calling skb_clone(), pskb_pull() and pskb_trim(). We instead
keep track of the offset and length of the content of each packet in
the sk_buff metadata. This means we don't do any allocation in the
receive path.
(3) Jumbo DATA packet parsing is now done in data_ready context. Rather
than cloning the packet once for each subpacket and pulling/trimming
it, we file the packet multiple times with an annotation for each
indicating which subpacket is there. From that we can directly
calculate the offset and length.
(4) A call's receive queue can be accessed without taking locks (memory
barriers do have to be used, though).
(5) Incoming calls are set up from preallocated resources and immediately
made live. They can than have packets queued upon them and ACKs
generated. If insufficient resources exist, DATA packet #1 is given a
BUSY reply and other DATA packets are discarded).
(6) sk_buffs no longer take a ref on their parent call.
To make this work, the following changes are made:
(1) Each call's receive buffer is now a circular buffer of sk_buff
pointers (rxtx_buffer) rather than a number of sk_buff_heads spread
between the call and the socket. This permits each sk_buff to be in
the buffer multiple times. The receive buffer is reused for the
transmit buffer.
(2) A circular buffer of annotations (rxtx_annotations) is kept parallel
to the data buffer. Transmission phase annotations indicate whether a
buffered packet has been ACK'd or not and whether it needs
retransmission.
Receive phase annotations indicate whether a slot holds a whole packet
or a jumbo subpacket and, if the latter, which subpacket. They also
note whether the packet has been decrypted in place.
(3) DATA packet window tracking is much simplified. Each phase has just
two numbers representing the window (rx_hard_ack/rx_top and
tx_hard_ack/tx_top).
The hard_ack number is the sequence number before base of the window,
representing the last packet the other side says it has consumed.
hard_ack starts from 0 and the first packet is sequence number 1.
The top number is the sequence number of the highest-numbered packet
residing in the buffer. Packets between hard_ack+1 and top are
soft-ACK'd to indicate they've been received, but not yet consumed.
Four macros, before(), before_eq(), after() and after_eq() are added
to compare sequence numbers within the window. This allows for the
top of the window to wrap when the hard-ack sequence number gets close
to the limit.
Two flags, RXRPC_CALL_RX_LAST and RXRPC_CALL_TX_LAST, are added also
to indicate when rx_top and tx_top point at the packets with the
LAST_PACKET bit set, indicating the end of the phase.
(4) Calls are queued on the socket 'receive queue' rather than packets.
This means that we don't need have to invent dummy packets to queue to
indicate abnormal/terminal states and we don't have to keep metadata
packets (such as ABORTs) around
(5) The offset and length of a (sub)packet's content are now passed to
the verify_packet security op. This is currently expected to decrypt
the packet in place and validate it.
However, there's now nowhere to store the revised offset and length of
the actual data within the decrypted blob (there may be a header and
padding to skip) because an sk_buff may represent multiple packets, so
a locate_data security op is added to retrieve these details from the
sk_buff content when needed.
(6) recvmsg() now has to handle jumbo subpackets, where each subpacket is
individually secured and needs to be individually decrypted. The code
to do this is broken out into rxrpc_recvmsg_data() and shared with the
kernel API. It now iterates over the call's receive buffer rather
than walking the socket receive queue.
Additional changes:
(1) The timers are condensed to a single timer that is set for the soonest
of three timeouts (delayed ACK generation, DATA retransmission and
call lifespan).
(2) Transmission of ACK and ABORT packets is effected immediately from
process-context socket ops/kernel API calls that cause them instead of
them being punted off to a background work item. The data_ready
handler still has to defer to the background, though.
(3) A shutdown op is added to the AF_RXRPC socket so that the AFS
filesystem can shut down the socket and flush its own work items
before closing the socket to deal with any in-progress service calls.
Future additional changes that will need to be considered:
(1) Make sure that a call doesn't hog the front of the queue by receiving
data from the network as fast as userspace is consuming it to the
exclusion of other calls.
(2) Transmit delayed ACKs from within recvmsg() when we've consumed
sufficiently more packets to avoid the background work item needing to
run.
Signed-off-by: David Howells <dhowells@redhat.com>
Make it possible for the data_ready handler called from the UDP transport
socket to completely instantiate an rxrpc_call structure and make it
immediately live by preallocating all the memory it might need. The idea
is to cut out the background thread usage as much as possible.
[Note that the preallocated structs are not actually used in this patch -
that will be done in a future patch.]
If insufficient resources are available in the preallocation buffers, it
will be possible to discard the DATA packet in the data_ready handler or
schedule a BUSY packet without the need to schedule an attempt at
allocation in a background thread.
To this end:
(1) Preallocate rxrpc_peer, rxrpc_connection and rxrpc_call structs to a
maximum number each of the listen backlog size. The backlog size is
limited to a maxmimum of 32. Only this many of each can be in the
preallocation buffer.
(2) For userspace sockets, the preallocation is charged initially by
listen() and will be recharged by accepting or rejecting pending
new incoming calls.
(3) For kernel services {,re,dis}charging of the preallocation buffers is
handled manually. Two notifier callbacks have to be provided before
kernel_listen() is invoked:
(a) An indication that a new call has been instantiated. This can be
used to trigger background recharging.
(b) An indication that a call is being discarded. This is used when
the socket is being released.
A function, rxrpc_kernel_charge_accept() is called by the kernel
service to preallocate a single call. It should be passed the user ID
to be used for that call and a callback to associate the rxrpc call
with the kernel service's side of the ID.
(4) Discard the preallocation when the socket is closed.
(5) Temporarily bump the refcount on the call allocated in
rxrpc_incoming_call() so that rxrpc_release_call() can ditch the
preallocation ref on service calls unconditionally. This will no
longer be necessary once the preallocation is used.
Note that this does not yet control the number of active service calls on a
client - that will come in a later patch.
A future development would be to provide a setsockopt() call that allows a
userspace server to manually charge the preallocation buffer. This would
allow user call IDs to be provided in advance and the awkward manual accept
stage to be bypassed.
Signed-off-by: David Howells <dhowells@redhat.com>
Remove the sk_buff count from the rxrpc_call struct as it's less useful
once we stop queueing sk_buffs.
Signed-off-by: David Howells <dhowells@redhat.com>
Convert the rxrpc_local::services list to an hlist so that it can be
accessed under RCU conditions more readily.
Signed-off-by: David Howells <dhowells@redhat.com>
Fix ASSERTCMP and ASSERTIFCMP to be able to handle signed values by casting
both parameters to the type of the first before comparing. Without this,
both values are cast to unsigned long, which means that checks for values
less than zero don't work.
The downside of this is that the state enum values in struct rxrpc_call and
struct rxrpc_connection can't be bitfields as __typeof__ can't handle them.
Signed-off-by: David Howells <dhowells@redhat.com>
