Provided by: libxs-dev_1.2.0-2_amd64 bug

NAME

       xs_getsockopt - get Crossroads socket option

SYNOPSIS

       int xs_getsockopt (void *socket, int option_name, void *option_value, size_t *option_len);

DESCRIPTION

       The xs_getsockopt() function shall retrieve the value for the option specified by the
       option_name argument for the Crossroads socket pointed to by the socket argument, and
       store it in the buffer pointed to by the option_value argument. The option_len argument is
       the size in bytes of the buffer pointed to by option_value; upon successful completion
       xs_getsockopt() shall modify the option_len argument to indicate the actual size of the
       option value stored in the buffer.

       The following options can be retrieved with the xs_getsockopt() function:

   XS_TYPE: Retrieve socket type
       The XS_TYPE option shall retrieve the socket type for the specified socket. The socket
       type is specified at socket creation time and cannot be modified afterwards.

       Option value type         int

       Option value unit         N/A

       Default value             N/A

       Applicable socket types   all

   XS_RCVMORE: More message data parts to follow
       The XS_RCVMORE option shall return True (1) if the message part last received from the
       socket was a data part with more parts to follow. If there are no data parts to follow,
       this option shall return False (0).

       Refer to xs_send(3) and xs_recv(3) for a detailed description of multi-part messages.

       Option value type         int

       Option value unit         boolean

       Default value             N/A

       Applicable socket types   all

   XS_SNDHWM: Retrieves high water mark for outbound messages
       The XS_SNDHWM option shall return the high water mark for outbound messages on the
       specified socket. The high water mark is a hard limit on the maximum number of outstanding
       messages the library shall queue in memory for any single peer that the specified socket
       is communicating with.

       If this limit has been reached the socket shall enter an exceptional state and depending
       on the socket type, the library shall take appropriate action such as blocking or dropping
       sent messages. Refer to the individual socket descriptions in xs_socket(3) for details on
       the exact action taken for each socket type.

       Option value type         int

       Option value unit         messages

       Default value             1000

       Applicable socket types   all

   XS_RCVHWM: Retrieve high water mark for inbound messages
       The XS_RCVHWM option shall return the high water mark for inbound messages on the
       specified socket. The high water mark is a hard limit on the maximum number of outstanding
       messages the library shall queue in memory for any single peer that the specified socket
       is communicating with.

       If this limit has been reached the socket shall enter an exceptional state and depending
       on the socket type, the library shall take appropriate action such as blocking or dropping
       sent messages. Refer to the individual socket descriptions in xs_socket(3) for details on
       the exact action taken for each socket type.

       Option value type         int

       Option value unit         messages

       Default value             1000

       Applicable socket types   all

   XS_AFFINITY: Retrieve I/O thread affinity
       The XS_AFFINITY option shall retrieve the I/O thread affinity for newly created
       connections on the specified socket.

       Affinity determines which threads from the Crossroads I/O thread pool associated with the
       socket’s context shall handle newly created connections. A value of zero specifies no
       affinity, meaning that work shall be distributed fairly among all I/O threads in the
       thread pool. For non-zero values, the lowest bit corresponds to thread 1, second lowest
       bit to thread 2 and so on. For example, a value of 3 specifies that subsequent connections
       on socket shall be handled exclusively by I/O threads 1 and 2.

       See also xs_init(3) for details on allocating the number of I/O threads for a specific
       context.

       Option value type         uint64_t

       Option value unit         N/A (bitmap)

       Default value             0

       Applicable socket types   N/A

   XS_IDENTITY: Set socket identity
       The XS_IDENTITY option shall retrieve the identity of the specified socket. Socket
       identity is used only by request/reply pattern. Namely, it can be used in tandem with a
       XS_XREP socket to route messages to the peer with specific identity.

       Identity should be at least one byte and at most 255 bytes long. Identities starting with
       binary zero are reserved for use by Crossroads infrastructure.

       Option value type         binary data

       Option value unit         N/A

       Default value             NULL

       Applicable socket types   all

   XS_RATE: Retrieve multicast data rate
       The XS_RATE option shall retrieve the maximum send or receive data rate for multicast
       transports using the specified socket.

       Option value type         int

       Option value unit         kilobits per second

       Default value             100

       Applicable socket types   all, when using multicast
                                 transports

   XS_RECOVERY_IVL: Get multicast recovery interval
       The XS_RECOVERY_IVL option shall retrieve the recovery interval for multicast transports
       using the specified socket. The recovery interval determines the maximum time in
       milliseconds that a receiver can be absent from a multicast group before unrecoverable
       data loss will occur.

       Option value type         int

       Option value unit         milliseconds

       Default value             10000

       Applicable socket types   all, when using multicast
                                 transports

   XS_SNDBUF: Retrieve kernel transmit buffer size
       The XS_SNDBUF option shall retrieve the underlying kernel transmit buffer size for the
       specified socket. A value of zero means that the OS default is in effect. For details
       refer to your operating system documentation for the SO_SNDBUF socket option.

       Option value type         int

       Option value unit         bytes

       Default value             0

       Applicable socket types   all

   XS_RCVBUF: Retrieve kernel receive buffer size
       The XS_RCVBUF option shall retrieve the underlying kernel receive buffer size for the
       specified socket. A value of zero means that the OS default is in effect. For details
       refer to your operating system documentation for the SO_RCVBUF socket option.

       Option value type         int

       Option value unit         bytes

       Default value             0

       Applicable socket types   all

   XS_LINGER: Retrieve linger period for socket shutdown
       The XS_LINGER option shall retrieve the linger period for the specified socket. The linger
       period determines how long pending messages which have yet to be sent to a peer shall
       linger in memory after a socket is closed with xs_close(3), and further affects the
       termination of the socket’s context with xs_term(3). The following outlines the different
       behaviours:

       ·   The default value of -1 specifies an infinite linger period. Pending messages shall
           not be discarded after a call to xs_close(); attempting to terminate the socket’s
           context with xs_term() shall block until all pending messages have been sent to a
           peer.

       ·   The value of 0 specifies no linger period. Pending messages shall be discarded
           immediately when the socket is closed with xs_close().

       ·   Positive values specify an upper bound for the linger period in milliseconds. Pending
           messages shall not be discarded after a call to xs_close(); attempting to terminate
           the socket’s context with xs_term() shall block until either all pending messages have
           been sent to a peer, or the linger period expires, after which any pending messages
           shall be discarded.

           Option value type         int
           Option value unit         milliseconds
           Default value             -1 (infinite)
           Applicable socket types   all

   XS_RECONNECT_IVL: Retrieve reconnection interval
       The XS_RECONNECT_IVL option shall retrieve the initial reconnection interval for the
       specified socket. The reconnection interval is the period the library shall wait between
       attempts to reconnect disconnected peers when using connection-oriented transports.

           Note
           The reconnection interval may be randomized by the library to prevent reconnection
           storms in topologies with a large number of peers per socket.

       Option value type         int

       Option value unit         milliseconds

       Default value             100

       Applicable socket types   all, only for
                                 connection-oriented transports

   XS_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval
       The XS_RECONNECT_IVL_MAX option shall retrieve the maximum reconnection interval for the
       specified socket. This is the maximum period the library shall wait between attempts to
       reconnect. On each reconnect attempt, the previous interval shall be doubled untill
       XS_RECONNECT_IVL_MAX is reached. This allows for exponential backoff strategy. Default
       value means no exponential backoff is performed and reconnect interval calculations are
       only based on XS_RECONNECT_IVL.

           Note
           Values less than XS_RECONNECT_IVL will be ignored.

       Option value type         int

       Option value unit         milliseconds

       Default value             0 (only use XS_RECONNECT_IVL)

       Applicable socket types   all, only for
                                 connection-oriented transport

   XS_BACKLOG: Retrieve maximum length of the queue of outstanding connections
       The XS_BACKLOG option shall retrieve the maximum length of the queue of outstanding peer
       connections for the specified socket; this only applies to connection-oriented transports.
       For details refer to your operating system documentation for the listen function.

       Option value type         int

       Option value unit         connections

       Default value             100

       Applicable socket types   all, only for
                                 connection-oriented transports

   XS_MAXMSGSIZE: Maximum acceptable inbound message size
       The option shall retrieve limit for the inbound messages. If a peer sends a message larger
       than XS_MAXMSGSIZE it is disconnected.

       Option value type         uint64_t

       Option value unit         bytes

       Default value             2^64-1

       Applicable socket types   all

   XS_MULTICAST_HOPS: Maximum network hops for multicast packets
       The option shall retrieve time-to-live used for outbound multicast packets. The default of
       1 means that the multicast packets don’t leave the local network.

       Option value type         int

       Option value unit         network hops

       Default value             1

       Applicable socket types   all, when using multicast
                                 transports

   XS_RCVTIMEO: Maximum time before a socket operation returns with EAGAIN
       Retrieve the timeout for recv operation on the socket. If the value is 0, xs_recv(3) will
       return immediately, with a EAGAIN error if there is no message to receive. If the value is
       -1, it will block until a message is available. For all other values, it will wait for a
       message for that amount of time before returning with an EAGAIN error.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1 (infinite)

       Applicable socket types   all

   XS_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN
       Retrieve the timeout for send operation on the socket. If the value is 0, xs_send(3) will
       return immediately, with a EAGAIN error if the message cannot be sent. If the value is -1,
       it will block until the message is sent. For all other values, it will try to send the
       message for that amount of time before returning with an EAGAIN error.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1 (infinite)

       Applicable socket types   all

   XS_IPV4ONLY: Retrieve IPv4-only socket override status
       Retrieve the underlying native socket type. A value of 1 will use IPv4 sockets, while the
       value of 0 will use IPv6 sockets. An IPv6 socket lets applications connect to and accept
       connections from both IPv4 and IPv6 hosts.

       Option value type         int

       Option value unit         boolean

       Default value             1 (true)

       Applicable socket types   all, when using TCP transport.

   XS_FD: Retrieve file descriptor associated with the socket
       The XS_FD option shall retrieve the file descriptor associated with the specified socket.
       The returned file descriptor can be used to integrate the socket into an existing event
       loop; the library shall signal any pending events on the socket in an edge-triggered
       fashion by making the file descriptor become ready for reading.

           Note
           The ability to read from the returned file descriptor does not necessarily indicate
           that messages are available to be read from, or can be written to, the underlying
           socket; applications must retrieve the actual event state with a subsequent retrieval
           of the XS_EVENTS option.

           Note
           The returned file descriptor is also used internally by the xs_send and xs_recv
           functions. As the descriptor is edge triggered, applications must update the state of
           XS_EVENTS after each invocation of xs_send or xs_recv.To be more explicit: after
           calling xs_send the socket may become readable (and vice versa) without triggering a
           read event on the file descriptor.

           Caution
           The returned file descriptor is intended for use with a poll or similar system call
           only. Applications must never attempt to read or write data to it directly, neither
           should they try to close it.

       Option value type         int on POSIX systems, SOCKET on
                                 Windows

       Option value unit         N/A

       Default value             N/A

       Applicable socket types   all

   XS_EVENTS: Retrieve socket event state
       The XS_EVENTS option shall retrieve the event state for the specified socket. The returned
       value is a bit mask constructed by OR’ing a combination of the following event flags:

       XS_POLLIN
           Indicates that at least one message may be received from the specified socket without
           blocking.

       XS_POLLOUT
           Indicates that at least one message may be sent to the specified socket without
           blocking.

       The combination of a file descriptor returned by the XS_FD option being ready for reading
       but no actual events returned by a subsequent retrieval of the XS_EVENTS option is valid;
       applications should simply ignore this case and restart their polling operation/event
       loop.

       Option value type         int

       Option value unit         N/A (flags)

       Default value             N/A

       Applicable socket types   all

   XS_KEEPALIVE: Enable transport keepalives
       When set to 1, this option enables use of protocol keepalives on the socket, if supported
       by the underlying transport protocol.

       Option value type         int

       Option value unit         boolean

       Default value             0 (false)

       Applicable socket types   all, when using TCP transport.

   XS_SURVEY_TIMEOUT: Retrieve deadline for the survey
       Specifies how long to wait for responses to the survey. After the interval expires, any
       firther calls to xs_recv() will return EAGAIN error. All the responses received later on
       will be silently discarded. Value of -1 means infinite.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1 (infinite)

       Applicable socket types   XS_SURVEYOR

RETURN VALUE

       The xs_getsockopt() function shall return zero if successful. Otherwise it shall return -1
       and set errno to one of the values defined below.

ERRORS

       EINVAL
           The requested option option_name is unknown, or the requested option_len or
           option_value is invalid, or the size of the buffer pointed to by option_value, as
           specified by option_len, is insufficient for storing the option value.

       ETERM
           The context associated with the specified socket was terminated.

       ENOTSOCK
           The provided socket was invalid.

       EINTR
           The operation was interrupted by delivery of a signal.

EXAMPLE

       Retrieving the high water mark for outgoing messages.

           /* Retrieve high water mark into sndhwm */
           int sndhwm;
           size_t sndhwm_size = sizeof (sndhwm);
           rc = xs_getsockopt (socket, XS_SNDHWM, &sndhwm, &sndhwm_size);
           assert (rc == 0);

SEE ALSO

       xs_setsockopt(3) xs_socket(3) xs(7)

AUTHORS

       The Crossroads documentation was written by Martin Sustrik <sustrik@250bpm.com[1]> and
       Martin Lucina <martin@lucina.net[2]>.

NOTES

        1. sustrik@250bpm.com
           mailto:sustrik@250bpm.com

        2. martin@lucina.net
           mailto:martin@lucina.net