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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_NEGOTIATE_FDS(3) sd_bus_negotiate_fds SD_BUS_NEGOTIATE_FDS(3)
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.
Errors
Returned errors may indicate the following problems:
-EPERM
The bus connection has already been started.
-EINVAL
An argument is invalid.
Added in version 246.
-ENOPKG
The bus cannot be resolved.
Added in version 246.
-ECHILD
The bus was created in a different process, library or module
instance.
Added in version 246.
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.
sd_bus_negotiate_fds(), sd_bus_negotiate_timestamp(), and
sd_bus_negotiate_creds() were added in version 212.
sd_bus_get_creds_mask() was added in version 246.
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)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~rc2 SD_BUS_NEGOTIATE_FDS(3)
Pages that refer to this page: sd-bus(3), sd_bus_message_get_monotonic_usec(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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