NAME

launchd APIs — interfaces for interacting with a launchd job.

SYNOPSIS

#include <launch.h>
#include <servers/bootstrap.h>

kern_return_t
bootstrap_check_in(mach_port_t bp, const name_t service_name, mach_port_t *sp);

int
launch_activate_socket(const char *name, int **fds, size_t *cnt);

DESCRIPTION

A launchd(8) job may have resources that are held on behalf of it while it is not running to facilitate launch-on-demand. These interfaces allow for the job to retrieve these resources as part of its initialization.

Currently supported resource types are XPC listener connections, Mach ports, and sockets. Use of XPC with launchd(8) is documented in the xpc(3) family of manual pages.

MACH PORTS

The bootstrap_check_in() routine allows for a launchd(8) job to retrieve the receive right to a Mach port that launchd(8) has created on behalf of the job. launchd(8) creates this port and advertises it in the appropriate Mach bootstrap namespace by parsing the MachServices entry of the job's launchd.plist(5). The first argument to bootstrap_check_in() should always be the bootstrap_port() global. The second argument should be the name of the service whose port you wish to retrieve, as specified as an entry in the job's MachServices dictionary. The final argument, upon successful return, will be the name of the receive right corresponding to the port that launchd(8) had advertised in the bootstrap namespace.

If the job closes the receive right to the port with mach_port_mod_refs() or exits, the receive right obtained by this routine will be send back to launchd(8) rather than being closed. This allows launchd to resume advertising the same port in the Mach bootstrap namespace and frees clients from the need to re-query for the send right to that port when the job dies.

SOCKETS

The launch_activate_socket() routine allows a launchd(8) job to retrieve a set of file descriptors corresponding to a socket service that launchd(8) has created and advertised on behalf of the job by parsing the Sockets entry in the job's launchd.plist(5). The first argument should be the name of the socket entry as specified in the launchd.plist(5). The second argument, upon output, will point to an array of integers whose count is filled into the third argument upon success. This array represents all the sockets that launchd(8) created corresponding to the entry in the job's Sockets dictionary. Depending on the properties specified, a single Sockets entry may have multiple descriptors created for it (one for IPv4 and one for IPv6, for example). This array is allocated on the heap, and it is the caller's responsibility to call free(3) to dispose of the memory when it is no longer needed.

RETURN VALUES

If launch_activate_socket() succeeds, zero is returned. In the event of failure, a non-zero POSIX-compatible error code indicating the nature of the error is returned. This error may be decoded with strerror(3).

If bootstrap_check_in() succeeds, KERN_SUCCESS is returned. In the event of failure, a non-zero error code that may be decoded with bootstrap_strerror().

ERRORS

bootstrap_check_in() will fail if:

[BOOTSTRAP_UNKNOWN_SERVICE]: The Mach service name specified does not exist in the caller's launchd.plist(5).
[BOOTSTRAP_SERVICE_ACTIVE]: The specified Mach service has already been checked in by the job.

launch_activate_socket() will fail if:

[ENOENT]: The socket name specified does not exist in the caller's launchd.plist(5).
[ESRCH]: The calling process is not managed by launchd(8).
[EALREADY]: The specified socket has already been activated.