NAME

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

SYNOPSIS

       #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);

DESCRIPTION

       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.

RETURN VALUE

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

   Errors
       Returned errors may indicate the following problems:

       -EPERM
           The bus connection has already been started.

       -EINVAL
           An argument is invalid.

       -ENOPKG
           The bus cannot be resolved.

       -ECHILD
           The bus was created in a different process.

NOTES

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

SEE ALSO

       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)