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Problem Report 1623 Details

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Report 1623 Actions

    Problem Report Number 1623
    Submitter's Classification Specification problem
    State Resolved
    Resolution Permanent Interpretation (PIN)
    Problem Resolution ID PIN.X.0180
    Raised 1997-09-01 08:00
    Updated 2003-03-13 08:00
    Published 1997-10-07 08:00
    Product Standard Sockets (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSU version 4.1.1
    Test Identification CAPI.os/sockets/connect 3,4,5,6,7,8
    Specification Networking Services Issue 4
    Location in Spec See Problem Text
    Problem Summary PIN4U.00046 This IR claims that historical behavior should be allowed in UNIX95 and/or UNIX98.
    Problem Text

    These tests are failing because of a difference in methods for
    specifying how many connections can be queued using the listen()
    routine.

    The Issue 4 Networking Services spec for listen() says:
    "The listen()function marks a connection-oriented socket,
    specified by the socket argument, as accepting connections,
    and limits the number of outstanding connections in the
    socket's listen queue to the value specified by the backlog
    argument."

    The historical BSD based implementation of listen has always been
    otherwise. The kernel has never taken this number literally and
    instead uses the algorithm:

    (3 * backlog / 2) +1

    The BSD (and SunOS) implementation has always, in fact, allowed 50%
    extra. The problem is that the count is really the sum of accepted
    connections and connections being accepted, and the 50% slop allowed
    for overlap between connections being set up and connections being
    handled. Now that we have raised the default dramatically, this is
    less important, but applications which set a particular small number
    may be confused.

    An example of an application that is broken by this "improvement"
    is sendmail. The distributed sendmail source asks for a queue length
    of 10. That is <<GROSSLY>> too small on any real system. Even the
    effective limit of 15 is far too small. The problem goes as 1/N. As
    N approaches 0, things get very bad. Going from 15 to 10 is a major
    change.

    The backlog fudge is not an optimization. It is designed to handle
    the needs of transports that require a half-open connection state.

    Having standards tests that require breaking legacy code is not only a
    very bad idea, it defies the spirit of the mission.

    The plot thickens with the release of the Networking Services (XNS)
    specification, Issue 5. The new spec for listen() sez:

    "The implementation may include incomplete connections in
    the queue subject to the queue limit. The implementation may also
    increase the specified queue limit internally if it includes
    such incomplete connections in the queue subject to the limit."

    Bottom line, we'd have to break our current (historical) implementation
    to brand for Unix 95 and then restore it to brand for Unix 98.
    Test Output

    TEST CASE: connect

    TEST PURPOSE #3
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) when the
    connection cannot be immediately established and
    O_NONBLOCK is not set for socket shall block until the
    connection is established or a timeout elapses.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 3777
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Notify child to delay and then accept
    TEST: connect blocks until connection accepted
    TEST: Duration of blocking
    ERROR: Process did not appear to block, expected: 2 secs (approx), actual: 0 secs
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    PREP: Child: delay
    3 FAIL

    TEST PURPOSE #4
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) when blocking
    is terminated due to expiration of the timeout shall
    abort the connection attempt, set errno to ETIMEDOUT,
    and return -1.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 2041
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set long alarm
    TEST: connect blocks until timeout elapses
    TEST: Return value
    ERROR: Call to connect unexpectedly succeeded
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to complete
    4 FAIL

    TEST PURPOSE #5
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) when blocking
    is interrupted by a signal shall set errno to EINTR,
    return -1, and establish the connection asynchronously.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 3321
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    TEST: connect blocks until interrupted
    ERROR: Call to connect unexpectedly succeeded
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    5 FAIL

    TEST PURPOSE #6
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) when the
    connection cannot be immediately established and
    O_NONBLOCK is set for socket shall return -1, set
    errno to EINPROGRESS, and establish the connection
    asynchronously.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.42.131, port = 2529
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    PREP: Child: accept queued connections
    PREP: Child: accept connection being asynchronously established
    PREP: Child: notify parent connections completed
    PREP: Child: wait for parent to complete test
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set O_NONBLOCK
    TEST: connect returns with EINPROGRESS
    TEST: Did not block
    PREP: Notify child to accept
    TEST: Await notification connections completed
    TEST: AF_UNIX SOCK_STREAM
    PREP: Create test sockaddr_un: path = ../tmp/unix.a01ELq
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set O_NONBLOCK
    TEST: connect returns with EINPROGRESS
    ERROR: Call to connect unexpectedly succeeded
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    6 FAIL

    TEST PURPOSE #7
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) when
    asynchronous connection establishment is in progress
    for socket shall return -1 and set errno to EALREADY.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 4941
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set O_NONBLOCK
    TEST: connect returns with EINPROGRESS
    TEST: Did not block
    TEST: connect returns with EALREADY
    ERROR: Call to connect failed unexpectedly, expected errno = EALREADY, errno = 133(EISCONN - Socket is connected)
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to complete test
    7 FAIL

    TEST PURPOSE #8
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    After a connection is asynchronously established due
    to a call to int connect(int socket, const struct
    sockaddr *address, size_t address_len) select() and
    poll() shall indicate socket is ready for writing.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.42.131, port = 3793
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set O_NONBLOCK
    TEST: connect returns with EINPROGRESS
    PREP: Notify child to accept
    TEST: Await notification connections completed
    TEST: Select reports socket ready to write
    TEST: Poll reports socket ready to write
    TEST: AF_UNIX SOCK_STREAM
    PREP: Create test sockaddr_un: path = ../tmp/unix.a01EAJ
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    PREP: Child: accept queued connections
    PREP: Child: accept connection being asynchronously established
    PREP: Child: notify parent connections completed
    PREP: Child: wait for parent to complete test
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    PREP: Set O_NONBLOCK
    TEST: connect returns with EINPROGRESS
    ERROR: Call to connect unexpectedly succeeded
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to become ready
    8 FAIL

    TEST CASE: listen

    TEST PURPOSE #2
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int listen(int socket, int backlog) when
    backlog is greater than or equal to 0 shall limit the
    number of connections in the socket's listen queue to
    that value.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 2549
    PREP: Create three sockets
    PREP: Wait for child to be ready
    PREP: Connect twice to fill queue
    TEST: Next connect is rejected
    TEST: Return value
    ERROR: connect call succeeded unexpectedly, returned 0
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of 2
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to complete test
    2 FAIL

    TEST PURPOSE #3
    If the implementation supports a communications domain
    and a connection-oriented socket type:
    A call to int listen(int socket, int backlog) when
    backlog is negative shall set the length of the
    socket's listen queue to 0.
    PREP: Get VSU_CONNECT_TIMEOUT configuration variable
    TEST: AF_INET SOCK_STREAM
    PREP: Create test sockaddr_in: address = 150.166.40.34, port = 2681
    PREP: Create a socket
    PREP: Wait for child to be ready
    TEST: connect is rejected
    TEST: Return value
    ERROR: connect call succeeded unexpectedly, returned 0
    PREP: Child: create socket
    PREP: Child: bind to socket
    PREP: Child: listen on socket with backlog of -1
    PREP: Child: tell parent ready
    PREP: Child: wait for parent to complete test
    3 FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    We recommend this request be refused.

    The specification is unambiguous in its requirements and these are
    accurately verified by the tests. This issue has been raised in the
    past with regard to BSD-derived implementations. The intent of the
    spec was reaffirmed each time. This parameter is required to define
    exactly the size of the queue.

    Further:

    > The plot thickens with the release of the Networking Services (XNS)
    > specification, Issue 5. The new spec for listen() sez:
    >
    > "The implementation may include incomplete connections in
    > the queue subject to the queue limit. The implementation may also
    > increase the specified queue limit internally if it includes
    > such incomplete connections in the queue subject to the limit."

    We don't believe this changes the issue here. The key phrase is
    "subject to the queue limit". That is, an implementation may use
    queue slots for partial connections, but the queue limit, as
    specified by the backlog parameter, must still be enforced. Thus
    the BSD behavior remains non-conforming.

    There are alternatives for conformance.

    The standard only requires that XPG4 functionality be present if
    _XOPEN_SOURCE is defined (see section 1.3 The Compilation Environment
    in the Networking standard), and UNIX95 functionality be present if
    XOPEN_SOURCE_EXTENDED=1 is defined as in the case of listen(). In
    Issue 5, _XOPEN_SOURCE=500 defines the compilation environment for
    UNIX98. Outside of this well-defined environment, interfaces may
    behave differently.

    It is common to have different behaviours depending on the
    compilation environment defined. Once an IUT is branded for UNIX98,
    it is likely that a UNIX95 mode will be retained for existing applications.
    UNIX95, UNIX95 behaviour will prevail depending on the XOPEN macros
    defined. Historical OS behavior may prevail if XOPEN macros are not defined.

    Also, please note that historical practice is not normative.
    Historical applications can certainly be affected by conformance
    to the UNIX95 standard, but there is no requirement that
    applications be compiled in a UNIX95 or UNIX98 environment.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution No Resolution Given
    Review Conclusion
    The change introduced in XNS 5 aligns with P1003.1g. This says that "If the
    protocol returns sockets in the CONNECTED state rather than the CONFIRMING
    state via the accept() function, the implementation may include incomplete
    connections in the queue subject to the queue limit. The implementation may
    also increase the specified queue limit internally if it includes such
    incomplete connections in the queue subject to this limit." (The "If the
    protocol returns . . " clause can be translated as "For TCP but not for ISO
    Transport.") This text is based on BSD practice and lends weight to the
    claim that historical implementations behave this way.

    The initial X/Open sockets specification was intended to reflect historical,
    specifically BSD, practice. It is likely that there was a mistake in the
    BSD man pages and that this mistake was simply copied into XNS 4.
    There seems to be a case here for a Permanent Interpretation.

    This should be forward to the XNET working group.

    Review Type Expert Group Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution No Resolution Given
    Review Conclusion
    The working group finds this a difficult area where further work is needed
    to clarify the specification. Meanwhile, a majority of the group is in
    favour of granting the request.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Permanent Interpretation (PIN)
    Review Conclusion
    A Permanent Interpretation is granted.

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