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15 Commits

Author SHA1 Message Date
David Howells
fdade4f69e rxrpc: Make service connection lookup always check for retry
When an RxRPC service packet comes in, the target connection is looked up
by an rb-tree search under RCU and a read-locked seqlock; the seqlock retry
check is, however, currently skipped if we got a match, but probably
shouldn't be in case the connection we found gets replaced whilst we're
doing a search.

Make the lookup procedure always go through need_seqretry(), even if the
lookup was successful.  This makes sure we always pick up on a write-lock
event.

On the other hand, since we don't take a ref on the object, but rely on RCU
to prevent its destruction after dropping the seqlock, I'm not sure this is
necessary.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-05 14:39:17 -07:00
David Howells
4722974d90 rxrpc: Implement service upgrade
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>
2017-06-05 14:30:49 +01:00
David Howells
68d6d1ae5c rxrpc: Separate the connection's protocol service ID from the lookup ID
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>
2017-06-05 14:30:49 +01:00
David Howells
2baec2c3f8 rxrpc: Support network namespacing
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>
2017-05-25 13:15:11 -04:00
David Howells
363deeab6d rxrpc: Add connection tracepoint and client conn state tracepoint
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>
2016-09-17 11:24:03 +01:00
David Howells
248f219cb8 rxrpc: Rewrite the data and ack handling code
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>
2016-09-08 11:10:12 +01:00
David Howells
00e907127e rxrpc: Preallocate peers, conns and calls for incoming service requests
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>
2016-09-08 11:10:12 +01:00
David Howells
45025bceef rxrpc: Improve management and caching of client connection objects
Improve the management and caching of client rxrpc connection objects.
From this point, client connections will be managed separately from service
connections because AF_RXRPC controls the creation and re-use of client
connections but doesn't have that luxury with service connections.

Further, there will be limits on the numbers of client connections that may
be live on a machine.  No direct restriction will be placed on the number
of client calls, excepting that each client connection can support a
maximum of four concurrent calls.

Note that, for a number of reasons, we don't want to simply discard a
client connection as soon as the last call is apparently finished:

 (1) Security is negotiated per-connection and the context is then shared
     between all calls on that connection.  The context can be negotiated
     again if the connection lapses, but that involves holding up calls
     whilst at least two packets are exchanged and various crypto bits are
     performed - so we'd ideally like to cache it for a little while at
     least.

 (2) If a packet goes astray, we will need to retransmit a final ACK or
     ABORT packet.  To make this work, we need to keep around the
     connection details for a little while.

 (3) The locally held structures represent some amount of setup time, to be
     weighed against their occupation of memory when idle.


To this end, the client connection cache is managed by a state machine on
each connection.  There are five states:

 (1) INACTIVE - The connection is not held in any list and may not have
     been exposed to the world.  If it has been previously exposed, it was
     discarded from the idle list after expiring.

 (2) WAITING - The connection is waiting for the number of client conns to
     drop below the maximum capacity.  Calls may be in progress upon it
     from when it was active and got culled.

     The connection is on the rxrpc_waiting_client_conns list which is kept
     in to-be-granted order.  Culled conns with waiters go to the back of
     the queue just like new conns.

 (3) ACTIVE - The connection has at least one call in progress upon it, it
     may freely grant available channels to new calls and calls may be
     waiting on it for channels to become available.

     The connection is on the rxrpc_active_client_conns list which is kept
     in activation order for culling purposes.

 (4) CULLED - The connection got summarily culled to try and free up
     capacity.  Calls currently in progress on the connection are allowed
     to continue, but new calls will have to wait.  There can be no waiters
     in this state - the conn would have to go to the WAITING state
     instead.

 (5) IDLE - The connection has no calls in progress upon it and must have
     been exposed to the world (ie. the EXPOSED flag must be set).  When it
     expires, the EXPOSED flag is cleared and the connection transitions to
     the INACTIVE state.

     The connection is on the rxrpc_idle_client_conns list which is kept in
     order of how soon they'll expire.

A connection in the ACTIVE or CULLED state must have at least one active
call upon it; if in the WAITING state it may have active calls upon it;
other states may not have active calls.

As long as a connection remains active and doesn't get culled, it may
continue to process calls - even if there are connections on the wait
queue.  This simplifies things a bit and reduces the amount of checking we
need do.


There are a couple flags of relevance to the cache:

 (1) EXPOSED - The connection ID got exposed to the world.  If this flag is
     set, an extra ref is added to the connection preventing it from being
     reaped when it has no calls outstanding.  This flag is cleared and the
     ref dropped when a conn is discarded from the idle list.

 (2) DONT_REUSE - The connection should be discarded as soon as possible and
     should not be reused.


This commit also provides a number of new settings:

 (*) /proc/net/rxrpc/max_client_conns

     The maximum number of live client connections.  Above this number, new
     connections get added to the wait list and must wait for an active
     conn to be culled.  Culled connections can be reused, but they will go
     to the back of the wait list and have to wait.

 (*) /proc/net/rxrpc/reap_client_conns

     If the number of desired connections exceeds the maximum above, the
     active connection list will be culled until there are only this many
     left in it.

 (*) /proc/net/rxrpc/idle_conn_expiry

     The normal expiry time for a client connection, provided there are
     fewer than reap_client_conns of them around.

 (*) /proc/net/rxrpc/idle_conn_fast_expiry

     The expedited expiry time, used when there are more than
     reap_client_conns of them around.


Note that I combined the Tx wait queue with the channel grant wait queue to
save space as only one of these should be in use at once.

Note also that, for the moment, the service connection cache still uses the
old connection management code.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-08-24 15:17:14 +01:00
David Howells
4d028b2c82 rxrpc: Dup the main conn list for the proc interface
The main connection list is used for two independent purposes: primarily it
is used to find connections to reap and secondarily it is used to list
connections in procfs.

Split the procfs list out from the reap list.  This allows us to stop using
the reap list for client connections when they acquire a separate
management strategy from service collections.

The client connections will not be on a management single list, and sometimes
won't be on a management list at all.  This doesn't leave them floating,
however, as they will also be on an rb-tree rooted on the socket so that the
socket can find them to dispatch calls.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-08-24 15:17:14 +01:00
Dan Carpenter
7acef60455 rxrpc: checking for IS_ERR() instead of NULL
The rxrpc_lookup_peer() function returns NULL on error, it never returns
error pointers.

Fixes: 8496af50eb ('rxrpc: Use RCU to access a peer's service connection tree')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-07-15 14:16:25 -07:00
David Howells
8496af50eb rxrpc: Use RCU to access a peer's service connection tree
Move to using RCU access to a peer's service connection tree when routing
an incoming packet.  This is done using a seqlock to trigger retrying of
the tree walk if a change happened.

Further, we no longer get a ref on the connection looked up in the
data_ready handler unless we queue the connection's work item - and then
only if the refcount > 0.


Note that I'm avoiding the use of a hash table for service connections
because each service connection is addressed by a 62-bit number
(constructed from epoch and connection ID >> 2) that would allow the client
to engage in bucket stuffing, given knowledge of the hash algorithm.
Peers, however, are hashed as the network address is less controllable by
the client.  The total number of peers will also be limited in a future
commit.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:51:14 +01:00
David Howells
e8d70ce177 rxrpc: Prune the contents of the rxrpc_conn_proto struct
Prune the contents of the rxrpc_conn_proto struct.  Most of the fields aren't
used anymore.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:51:14 +01:00
David Howells
001c112249 rxrpc: Maintain an extra ref on a conn for the cache list
Overhaul the usage count accounting for the rxrpc_connection struct to make
it easier to implement RCU access from the data_ready handler.

The problem is that currently we're using a lock to prevent the garbage
collector from trying to clean up a connection that we're contemplating
unidling.  We could just stick incoming packets on the connection we find,
but we've then got a problem that we may race when dispatching a work item
to process it as we need to give that a ref to prevent the rxrpc_connection
struct from disappearing in the meantime.

Further, incoming packets may get discarded if attached to an
rxrpc_connection struct that is going away.  Whilst this is not a total
disaster - the client will presumably resend - it would delay processing of
the call.  This would affect the AFS client filesystem's service manager
operation.

To this end:

 (1) We now maintain an extra count on the connection usage count whilst it
     is on the connection list.  This mean it is not in use when its
     refcount is 1.

 (2) When trying to reuse an old connection, we only increment the refcount
     if it is greater than 0.  If it is 0, we replace it in the tree with a
     new candidate connection.

 (3) Two connection flags are added to indicate whether or not a connection
     is in the local's client connection tree (used by sendmsg) or the
     peer's service connection tree (used by data_ready).  This makes sure
     that we don't try and remove a connection if it got replaced.

     The flags are tested under lock with the removal operation to prevent
     the reaper from killing the rxrpc_connection struct whilst someone
     else is trying to effect a replacement.

     This could probably be alleviated by using memory barriers between the
     flag set/test and the rb_tree ops.  The rb_tree op would still need to
     be under the lock, however.

 (4) When trying to reap an old connection, we try to flip the usage count
     from 1 to 0.  If it's not 1 at that point, then it must've come back
     to life temporarily and we ignore it.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:50:04 +01:00
David Howells
d991b4a32f rxrpc: Move peer lookup from call-accept to new-incoming-conn
Move the lookup of a peer from a call that's being accepted into the
function that creates a new incoming connection.  This will allow us to
avoid incrementing the peer's usage count in some cases in future.

Note that I haven't bother to integrate rxrpc_get_addr_from_skb() with
rxrpc_extract_addr_from_skb() as I'm going to delete the former in the very
near future.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:49:57 +01:00
David Howells
7877a4a4bd rxrpc: Split service connection code out into its own file
Split the service-specific connection code out into into its own file.  The
client-specific code has already been split out.  This will leave just the
common code in the original file.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:49:35 +01:00