illumos: manual page: door

DOOR_CREATE(3C) Standard C Library Functions DOOR_CREATE(3C)

NAME

door_create - create a door descriptor

SYNOPSIS

cc -mt [ flag... ] file... [ library... ]
#include <door.h>

int door_create(void (*server_procedure) (void *cookie, char *argp,
size_t arg_size, door_desc_t *dp, uint_t n_desc), void *cookie,
uint_t attributes);

DESCRIPTION

The door_create() function creates a door descriptor that describes the
procedure specified by the function server_procedure. The data item,
cookie, is associated with the door descriptor, and is passed as an
argument to the invoked function server_procedure during door_call(3C)
invocations. Other arguments passed to server_procedure from an
associated door_call() are placed on the stack and include argp and dp.
The argp argument points to arg_size bytes of data and the dp argument
points to n_desc door_desc_t structures. The attributes argument
specifies attributes associated with the newly created door. Valid values
for attributes are constructed by OR-ing one or more of the following
values:

DOOR_UNREF

Delivers a special invocation on the door when the number of
descriptors that refer to this door drops to one. In order to trigger
this condition, more than one descriptor must have referred to this
door at some time. DOOR_UNREF_DATA designates an unreferenced
invocation, as the argp argument passed to server_procedure. In the
case of an unreferenced invocation, the values for arg_size, dp and
n_did are 0. Only one unreferenced invocation is delivered on behalf
of a door.

DOOR_UNREF_MULTI

Similar to DOOR_UNREF, except multiple unreferenced invocations can
be delivered on the same door if the number of descriptors referring
to the door drops to one more than once. Since an additional
reference may have been passed by the time an unreferenced invocation
arrives, the DOOR_IS_UNREF attribute returned by the door_info(3C)
call can be used to determine if the door is still unreferenced.

DOOR_PRIVATE

Maintains a separate pool of server threads on behalf of the door.
Server threads are associated with a door's private server pool using
door_bind(3C).

DOOR_REFUSE_DESC

Any attempt to call door_call(3C) on this door with argument
descriptors will fail with ENOTSUP. When this flag is set, the door's
server procedure will always be invoked with an n_desc argument of 0.

DOOR_NO_CANCEL

Clients which abort calls to door_call() on this door will not cause
the cancellation of the server thread handling the request. See
cancellation(7).

The descriptor returned from door_create() will be marked as close on
exec (FD_CLOEXEC). Information about a door is available for all clients
of a door using door_info(). Applications concerned with security should
not place secure information in door data that is accessible by
door_info(). In particular, secure data should not be stored in the data
item cookie.

By default, additional threads are created as needed to handle concurrent
door_call() invocations. See door_server_create(3C) for information on
how to change this behavior.

A process can advertise a door in the file system name space using
fattach(3C).

After creation, door_setparam(3C) can be used to set limits on the amount
of data and descriptors clients can send over the door.

RETURN VALUES

Upon successful completion, door_create() returns a non-negative value.
Otherwise, door_create returns -1 and sets errno to indicate the error.

ERRORS

The door_create() function will fail if:

EINVAL
Invalid attributes are passed.

EMFILE
The process has too many open descriptors.

EXAMPLES

Example 1: Create a door and use fattach() to advertise the door in the

file system namespace.

The following example creates a door and uses fattach() to advertise the
door in the file system namespace.

void
server(void *cookie, char *argp, size_t arg_size, door_desc_t *dp,
uint_t n_desc)
{
door_return(NULL, 0, NULL, 0);
/* NOTREACHED */
}

int
main(int argc, char *argv[])
{
int did;
struct stat buf;

if ((did = door_create(server, 0, 0)) < 0) {
perror("door_create");
exit(1);
}

/* make sure file system location exists */
if (stat("/tmp/door", &buf) < 0) {
int newfd;
if ((newfd = creat("/tmp/door", 0444)) < 0) {
perror("creat");
exit(1);
}
(void) close(newfd);
}

/* make sure nothing else is attached */
(void) fdetach("/tmp/door");

/* attach to file system */
if (fattach(did, "/tmp/door") < 0) {
perror("fattach");
exit(2);
}
[...]
}

ATTRIBUTES