согласование функций управления на шинных соединениях (control feature negotiation on bus connections)
Имя (Name)
sd_bus_negotiate_fds, sd_bus_negotiate_timestamp,
sd_bus_negotiate_creds, sd_bus_get_creds_mask - Control feature
negotiation on bus connections
Синопсис (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);
Описание (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.
Возвращаемое значение (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.
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (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)
