Provided by: libsystemd-dev_251.4-1ubuntu7_amd64 bug


       sd_bus_negotiate_fds, sd_bus_negotiate_timestamp, sd_bus_negotiate_creds,
       sd_bus_get_creds_mask - Control feature negotiation on bus connections


       #include <systemd/sd-bus.h>

       int sd_bus_negotiate_fds(sd_bus *bus, int b);

       int sd_bus_negotiate_timestamp(sd_bus *bus, int b);

       int sd_bus_negotiate_creds(sd_bus *bus, int b, uint64_t mask);

       int sd_bus_get_creds_mask(sd_bus *bus, uint64_t *mask);


       sd_bus_negotiate_fds() controls whether file descriptor passing shall be negotiated for
       the specified bus connection. It takes a bus object and a boolean, which, when true,
       enables file descriptor passing, and, when false, disables it. Note that not all
       transports and servers support file descriptor passing. In particular, networked
       transports generally do not support file descriptor passing. To find out whether file
       descriptor passing is available after negotiation, use sd_bus_can_send(3) and pass
       SD_BUS_TYPE_UNIX_FD. Note that file descriptor passing is always enabled for both sending
       and receiving or for neither, but never only in one direction. By default, file descriptor
       passing is negotiated for all connections.

       sd_bus_negotiate_timestamp() controls whether implicit sender timestamps shall be attached
       automatically to all incoming messages. Takes a bus object and a boolean, which, when
       true, enables timestamping, and, when false, disables it. Use
       sd_bus_message_get_monotonic_usec(3), sd_bus_message_get_realtime_usec(3),
       sd_bus_message_get_seqnum(3) to query the timestamps of incoming messages. If negotiation
       is disabled or not supported, these calls will fail with -ENODATA. Note that currently no
       transports support timestamping of messages. By default, message timestamping is not
       negotiated for connections.

       sd_bus_negotiate_creds() controls whether and which implicit sender credentials shall be
       attached automatically to all incoming messages. Takes a bus object and a boolean
       indicating whether to enable or disable the credential parts encoded in the bit mask value
       argument. Note that not all transports support attaching sender credentials to messages,
       or do not support all types of sender credential parameters, or might suppress them under
       certain circumstances for individual messages. Specifically, dbus1 only supports
       SD_BUS_CREDS_UNIQUE_NAME. The sender credentials are suitable for authorization decisions.
       By default, only SD_BUS_CREDS_WELL_KNOWN_NAMES and SD_BUS_CREDS_UNIQUE_NAME are enabled.
       In fact, these two credential fields are always sent along and cannot be turned off.

       sd_bus_get_creds_mask() returns the set of sender credentials that was negotiated to be
       attached to all incoming messages in mask. This value is an upper boundary only. Hence,
       always make sure to explicitly check which credentials are attached to a specific message
       before using it.

       The sd_bus_negotiate_fds() function may be called only before the connection has been
       started with sd_bus_start(3). Both sd_bus_negotiate_timestamp() and
       sd_bus_negotiate_creds() may also be called after a connection has been set up. Note that,
       when operating on a connection that is shared between multiple components of the same
       program (for example via sd_bus_default(3)), it is highly recommended to only enable
       additional per message metadata fields, but never disable them again, in order not to
       disable functionality needed by other components.


       On success, these functions return a non-negative integer. On failure, they return a
       negative errno-style error code.

       Returned errors may indicate the following problems:

           The bus connection has already been started.

           An argument is invalid.

           The bus cannot be resolved.

           The bus was created in a different process.


       These APIs are implemented as a shared library, which can be compiled and linked to with
       the libsystemd pkg-config(1) file.


       systemd(1), sd-bus(3), sd_bus_start(3), sd_bus_can_send(3),
       sd_bus_message_get_monotonic_usec(3), sd_bus_message_get_realtime_usec(3),
       sd_bus_message_get_seqnum(3), sd_bus_message_get_creds(3)