OpenAFS Master Repository branch, master, updated. BP-openafs-stable-1_8_x-223-gc553170

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit c553170bcf3b97ba3745f21040c8e07b128ef983
Author: Jeffrey Altman <jaltman@auristor.com>
Date:   Wed Jun 6 21:23:14 2018 -0400

    rx: reset packet header userStatus field on reuse
    
    OpenAFS Rx fails to set the rx packet header userStatus field for most
    packets sent other than type RX_PACKET_TYPE_ACK.  If the userStatus
    field is not set, its value will be random garbage based upon the
    prior use of the memory allocated to the rx_packet.
    
    This change explicitly sets the userStatus field to zero for all
    DATA and Special packet types.
    
    Background
    ----------
    
    OpenAFS Rx allocates a pool of rx_packet structures that are reused
    for both incoming and outgoing Rx packets throughout the lifetime
    of the process (or kernel module).
    
    The rx packet header field userStatus is set by rxi_Send() to
    rx_call.localStatus.  rxi_Send() is called from both rxi_SendAck()
    when sending RX_PACKET_TYPE_ACK packets and from rxi_SendSpecial()
    when called with a non-NULL call structure (RX_PACKET_TYPE_BUSY,
    RX_PACKET_TYPE_ACKALL, or RX_PACKET_TYPE_ABORT).  rx_call.localStatus
    defaults to zero and can be modified by the application calling
    rx_SetLocalStatus().
    
    The userStatus field is neither set nor reset when sending
    RX_PACKET_TYPE_DATA packets and all packets sent without a call
    structure.  When allocated packets are reused in these cases, the
    value of the userStatus leaks from the prior packet use.  The
    userStatus field is expected to be zero unless intentionally set by
    the application protocol to another value.
    
    The AFS3 suite of rx services uses the rx_header.userStatus field
    only in the RXAFS service and only as part of the definition
    for RXAFS_StoreData and RXAFS_StoreData64 RPCs.  The StoreData RPCs
    use the rx_header.userStatus field as an out-of-band communication
    mechanism that permits the fileserver to signal to the cache manager
    when the RXAFS_StoreData[64] has been assigned to an application
    worker (thread) and the worker has acquired all of the required locks
    and other resources necessary to complete the RPC.  This signal can be
    sent before all of the application data has been received.  The cache
    manager reads the userStatus value via rx_GetRemoteStatus().  When
    bit-0 of the remote status value equals one and CSafeStore mode is
    disabled, the cache manager can wakeup any threads blocked waiting for
    the store operation to complete.
    
    Cache managers that perform a workload heavy in RXAFS_StoreData[64] RPCs
    will end up with an increasing percentage of packets in which the
    userStatus field is one instead of zero.
    
    Fileservers processing a workload heavy in RXAFS_StoreData[64] RPCs
    will likewise end up with an increasing percentage of packets in which
    the userStatus field is one instead of zero.
    
    Cache managers and Fileservers will therefore send DATA and call free
    special packets with a non-zero userStatus field to peer services
    (RXAFS, RXAFSCB, VL, PR).
    
    The failure to reset the userStatus field has not been a problem in
    the past because only the OpenAFS cache manager has ever queried the
    userStatus via rx_GetRemoteStatus() and only when issuing
    RXAFS_StoreData[64] RPCs.
    
    Failure to correct this flaw interferes with future use of the userStatus
    field in yet to be registered AFS3 RPCs and existing non-AFS3 services
    that make use of the userStatus when sending data to a service.
    
    Change-Id: I32c0bba93b8e5197036d92168956b6e2a95406fb
    FIXES: 134554
    Reviewed-on: https://gerrit.openafs.org/13165
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

 src/rx/rx_packet.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

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