09 Mar, 2018

1 commit

  • [ Upstream commit 93c62c45ed5fad1b87e3a45835b251cd68de9c46 ]

    All the kernel_sendmsg() calls in rxrpc_send_data_packet() need to send
    both parts of the iov[] buffer, but one of them does not. Fix it so that
    it does.

    Without this, short IPv6 rxrpc DATA packets may be seen that have the rxrpc
    header included, but no payload.

    Fixes: 5a924b8951f8 ("rxrpc: Don't store the rxrpc header in the Tx queue sk_buffs")
    Reported-by: Marc Dionne
    Signed-off-by: David Howells
    Signed-off-by: David S. Miller
    Signed-off-by: Greg Kroah-Hartman

    David Howells
     

29 Aug, 2017

1 commit

  • Fix IPv6 support in AF_RXRPC in the following ways:

    (1) When extracting the address from a received IPv4 packet, if the local
    transport socket is open for IPv6 then fill out the sockaddr_rxrpc
    struct for an IPv4-mapped-to-IPv6 AF_INET6 transport address instead
    of an AF_INET one.

    (2) When sending CHALLENGE or RESPONSE packets, the transport length needs
    to be set from the sockaddr_rxrpc::transport_len field rather than
    sizeof() on the IPv4 transport address.

    (3) When processing an IPv4 ICMP packet received by an IPv6 socket, set up
    the address correctly before searching for the affected peer.

    Signed-off-by: David Howells

    David Howells
     

05 Jun, 2017

1 commit

  • 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

    David Howells
     

06 Oct, 2016

3 commits

  • Don't request an ACK on the last DATA packet of a call's Tx phase as for a
    client there will be a reply packet or some sort of ACK to shift phase. If
    the ACK is requested, OpenAFS sends a REQUESTED-ACK ACK with soft-ACKs in
    it and doesn't follow up with a hard-ACK.

    If we don't set the flag, OpenAFS will send a DELAY ACK that hard-ACKs the
    reply data, thereby allowing the call to terminate cleanly.

    Signed-off-by: David Howells

    David Howells
     
  • 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

    David Howells
     
  • 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
    Signed-off-by: David Howells

    David Howells
     

30 Sep, 2016

2 commits

  • Set the request-ACK on more DATA packets whilst we're in slow start mode so
    that we get sufficient ACKs back to supply information to configure the
    window.

    Signed-off-by: David Howells

    David Howells
     
  • 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

    David Howells
     

25 Sep, 2016

2 commits

  • 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

    David Howells
     
  • 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

    David Howells
     

23 Sep, 2016

3 commits

  • 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

    David Howells
     
  • 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

    David Howells
     
  • rxrpc_send_call_packet() is invoking the tx_ack tracepoint before it checks
    whether there's an ACK to transmit (another thread may jump in and transmit
    it).

    Fix this by only invoking the tracepoint if we get a valid ACK to transmit.

    Further, only allocate a serial number if we're going to actually transmit
    something.

    Signed-off-by: David Howells

    David Howells
     

22 Sep, 2016

4 commits

  • 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

    David Howells
     
  • 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

    David Howells
     
  • 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

    David Howells
     
  • 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

    David Howells
     

17 Sep, 2016

6 commits

  • Add a configuration option to inject packet loss by discarding
    approximately every 8th packet received and approximately every 8th DATA
    packet transmitted.

    Note that no locking is used, but it shouldn't really matter.

    Signed-off-by: David Howells

    David Howells
     
  • 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

    David Howells
     
  • Add a tracepoint to log information about ACK transmission.

    Signed-off-by: David Howels

    David Howells
     
  • rxrpc_send_call_packet() should use type in both its switch-statements
    rather than using pkt->whdr.type. This might give the compiler an easier
    job of uninitialised variable checking.

    Signed-off-by: David Howells

    David Howells
     
  • Don't transmit an ACK if call->ackr_reason in unset. There's the
    possibility of a race between recvmsg() sending an ACK and the background
    processing thread trying to send the same one.

    Signed-off-by: David Howells

    David Howells
     
  • Add CONFIG_AF_RXRPC_IPV6 and make the IPv6 support code conditional on it.
    This is then made conditional on CONFIG_IPV6.

    Without this, the following can be seen:

    net/built-in.o: In function `rxrpc_init_peer':
    >> peer_object.c:(.text+0x18c3c8): undefined reference to `ip6_route_output_flags'

    Reported-by: kbuild test robot
    Signed-off-by: David Howells
    Signed-off-by: David S. Miller

    David Howells
     

14 Sep, 2016

3 commits

  • Add IPv6 support to AF_RXRPC. With this, AF_RXRPC sockets can be created:

    service = socket(AF_RXRPC, SOCK_DGRAM, PF_INET6);

    instead of:

    service = socket(AF_RXRPC, SOCK_DGRAM, PF_INET);

    The AFS filesystem doesn't support IPv6 at the moment, though, since that
    requires upgrades to some of the RPC calls.

    Note that a good portion of this patch is replacing "%pI4:%u" in print
    statements with "%pISpc" which is able to handle both protocols and print
    the port.

    Signed-off-by: David Howells

    David Howells
     
  • There are two places that want to transmit a packet in response to one just
    received and manually pick the address to reply to out of the sk_buff.
    Make them use rxrpc_extract_addr_from_skb() instead so that IPv6 is handled
    automatically.

    Signed-off-by: David Howells

    David Howells
     
  • 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

    David Howells
     

08 Sep, 2016

1 commit

  • 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

    David Howells
     

07 Sep, 2016

1 commit

  • rxrpc calls shouldn't hold refs on the sock struct. This was done so that
    the socket wouldn't go away whilst the call was in progress, such that the
    call could reach the socket's queues.

    However, we can mark the socket as requiring an RCU release and rely on the
    RCU read lock.

    To make this work, we do:

    (1) rxrpc_release_call() removes the call's call user ID. This is now
    only called from socket operations and not from the call processor:

    rxrpc_accept_call() / rxrpc_kernel_accept_call()
    rxrpc_reject_call() / rxrpc_kernel_reject_call()
    rxrpc_kernel_end_call()
    rxrpc_release_calls_on_socket()
    rxrpc_recvmsg()

    Though it is also called in the cleanup path of
    rxrpc_accept_incoming_call() before we assign a user ID.

    (2) Pass the socket pointer into rxrpc_release_call() rather than getting
    it from the call so that we can get rid of uninitialised calls.

    (3) Fix call processor queueing to pass a ref to the work queue and to
    release that ref at the end of the processor function (or to pass it
    back to the work queue if we have to requeue).

    (4) Skip out of the call processor function asap if the call is complete
    and don't requeue it if the call is complete.

    (5) Clean up the call immediately that the refcount reaches 0 rather than
    trying to defer it. Actual deallocation is deferred to RCU, however.

    (6) Don't hold socket refs for allocated calls.

    (7) Use the RCU read lock when queueing a message on a socket and treat
    the call's socket pointer according to RCU rules and check it for
    NULL.

    We also need to use the RCU read lock when viewing a call through
    procfs.

    (8) Transmit the final ACK/ABORT to a client call in rxrpc_release_call()
    if this hasn't been done yet so that we can then disconnect the call.
    Once the call is disconnected, it won't have any access to the
    connection struct and the UDP socket for the call work processor to be
    able to send the ACK. Terminal retransmission will be handled by the
    connection processor.

    (9) Release all calls immediately on the closing of a socket rather than
    trying to defer this. Incomplete calls will be aborted.

    The call refcount model is much simplified. Refs are held on the call by:

    (1) A socket's user ID tree.

    (2) A socket's incoming call secureq and acceptq.

    (3) A kernel service that has a call in progress.

    (4) A queued call work processor. We have to take care to put any call
    that we failed to queue.

    (5) sk_buffs on a socket's receive queue. A future patch will get rid of
    this.

    Whilst we're at it, we can do:

    (1) Get rid of the RXRPC_CALL_EV_RELEASE event. Release is now done
    entirely from the socket routines and never from the call's processor.

    (2) Get rid of the RXRPC_CALL_DEAD state. Calls now end in the
    RXRPC_CALL_COMPLETE state.

    (3) Get rid of the rxrpc_call::destroyer work item. Calls are now torn
    down when their refcount reaches 0 and then handed over to RCU for
    final cleanup.

    (4) Get rid of the rxrpc_call::deadspan timer. Calls are cleaned up
    immediately they're finished with and don't hang around.
    Post-completion retransmission is handled by the connection processor
    once the call is disconnected.

    (5) Get rid of the dead call expiry setting as there's no longer a timer
    to set.

    (6) rxrpc_destroy_all_calls() can just check that the call list is empty.

    Signed-off-by: David Howells

    David Howells
     

05 Sep, 2016

1 commit


02 Sep, 2016

1 commit

  • 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
    Signed-off-by: David S. Miller

    David Howells
     

30 Aug, 2016

3 commits

  • Pass struct socket * to more rxrpc kernel interface functions. They should
    be starting from this rather than the socket pointer in the rxrpc_call
    struct if they need to access the socket.

    I have left:

    rxrpc_kernel_is_data_last()
    rxrpc_kernel_get_abort_code()
    rxrpc_kernel_get_error_number()
    rxrpc_kernel_free_skb()
    rxrpc_kernel_data_consumed()

    unmodified as they're all about to be removed (and, in any case, don't
    touch the socket).

    Signed-off-by: David Howells

    David Howells
     
  • Add a trace event for debuging rxrpc_call struct usage.

    Signed-off-by: David Howells

    David Howells
     
  • Condense the terminal states of a call state machine to a single state,
    plus a separate completion type value. The value is then set, along with
    error and abort code values, only when the call is transitioned to the
    completion state.

    Helpers are provided to simplify this.

    Signed-off-by: David Howells

    David Howells
     

24 Aug, 2016

1 commit

  • 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

    David Howells
     

23 Aug, 2016

2 commits

  • Use a tracepoint to log various skb accounting points to help in debugging
    refcounting errors.

    Signed-off-by: David Howells

    David Howells
     
  • Do a little tidying of the rxrpc_call struct:

    (1) in_clientflag is no longer compared against the value that's in the
    packet, so keeping it in this form isn't necessary. Use a flag in
    flags instead and provide a pair of wrapper functions.

    (2) We don't read the epoch value, so that can go.

    (3) Move what remains of the data that were used for hashing up in the
    struct to be with the channel number.

    (4) Get rid of the local pointer. We can get at this via the socket
    struct and we only use this in the procfs viewer.

    Signed-off-by: David Howells

    David Howells
     

22 Jun, 2016

4 commits

  • The rxrpc_transport struct is now redundant, given that the rxrpc_peer
    struct is now per peer port rather than per peer host, so get rid of it.

    Service connection lists are transferred to the rxrpc_peer struct, as is
    the conn_lock. Previous patches moved the client connection handling out
    of the rxrpc_transport struct and discarded the connection bundling code.

    Signed-off-by: David Howells

    David Howells
     
  • Kill off the concept of maintaining a bundle of connections to a particular
    target service to increase the number of call slots available for any
    beyond four for that service (there are four call slots per connection).

    This will make cleaning up the connection handling code easier and
    facilitate removal of the rxrpc_transport struct. Bundling can be
    reintroduced later if necessary.

    Signed-off-by: David Howells

    David Howells
     
  • Make rxrpc_send_packet() take a connection not a transport as part of the
    phasing out of the rxrpc_transport struct.

    Whilst we're at it, rename the function to rxrpc_send_data_packet() to
    differentiate it from the other packet sending functions.

    Signed-off-by: David Howells

    David Howells
     
  • "Exclusive connections" are meant to be used for a single client call and
    then scrapped. The idea is to limit the use of the negotiated security
    context. The current code, however, isn't doing this: it is instead
    restricting the socket to a single virtual connection and doing all the
    calls over that.

    This is changed such that the socket no longer maintains a special virtual
    connection over which it will do all the calls, but rather gets a new one
    each time a new exclusive call is made.

    Further, using a socket option for this is a poor choice. It should be
    done on sendmsg with a control message marker instead so that calls can be
    marked exclusive individually. To that end, add RXRPC_EXCLUSIVE_CALL
    which, if passed to sendmsg() as a control message element, will cause the
    call to be done on an single-use connection.

    The socket option (RXRPC_EXCLUSIVE_CONNECTION) still exists and, if set,
    will override any lack of RXRPC_EXCLUSIVE_CALL being specified so that
    programs using the setsockopt() will appear to work the same.

    Signed-off-by: David Howells

    David Howells