x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_NEGOTIATE_FDS(3) sd_bus_negotiate_fds SD_BUS_NEGOTIATE_FDS(3)
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, library or module
instance.
NOTES
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
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)
systemd 254 SD_BUS_NEGOTIATE_FDS(3)
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