STREAMIO(4I) Ioctl Requests STREAMIO(4I)

NAME

streamio - STREAMS ioctl commands

SYNOPSIS

#include <sys/types.h>
#include <stropts.h>
#include <sys/conf.h>

int
ioctl(int fildes, int command, ... /*arg*/);

DESCRIPTION

STREAMS (see Intro(3)) ioctl() commands are a subset of the ioctl(2)
commands and perform a variety of control functions on streams.

The fildes argument is an open file descriptor that refers to a stream.
The command argument determines the control function to be performed as
described below. The arg argument represents additional information that
is needed by this command. The type of arg depends upon the command, but
it is generally an integer or a pointer to a command-specific data
structure. The command and arg arguments are interpreted by the STREAM
head. Certain combinations of these arguments may be passed to a module or
driver in the stream.

Since these STREAMS commands are ioctls, they are subject to the errors
described in ioctl(2). In addition to those errors, the call will fail
with errno set to EINVAL, without processing a control function, if the
STREAM referenced by fildes is linked below a multiplexor, or if command is
not a valid value for a stream.

Also, as described in ioctl(2), STREAMS modules and drivers can detect
errors. In this case, the module or driver sends an error message to the
STREAM head containing an error value. This causes subsequent calls to
fail with errno set to this value.

IOCTLS

The following ioctl() commands, with error values indicated, are applicable
to all STREAMS files:

I_PUSH Pushes the module whose name is pointed to by arg onto the top
of the current stream, just below the STREAM head. If the
STREAM is a pipe, the module will be inserted between the
stream heads of both ends of the pipe. It then calls the open
routine of the newly-pushed module. On failure, errno is set
to one of the following values:

EINVAL Invalid module name.

EFAULT arg points outside the allocated address space.

ENXIO Open routine of new module failed.

ENXIO Hangup received on fildes.

ENOTSUP Pushing a module is not supported on this stream.

I_POP Removes the module just below the STREAM head of the STREAM
pointed to by fildes. To remove a module from a pipe requires
that the module was pushed on the side it is being removed
from. arg should be 0 in an I_POP request. On failure, errno
is set to one of the following values:

EINVAL No module present in the stream.

ENXIO Hangup received on fildes.

EPERM Attempt to pop through an anchor by an unprivileged
process.

ENOTSUP Removal is not supported.

I_ANCHOR Positions the stream anchor to be at the stream's module
directly below the stream head. Once this has been done, only
a privileged process may pop modules below the anchor on the
stream. arg must be 0 in an I_ANCHOR request. On failure,
errno is set to the following value:

EINVAL Request to put an anchor on a pipe.

I_LOOK Retrieves the name of the module just below the stream head of
the stream pointed to by fildes, and places it in a null
terminated character string pointed at by arg. The buffer
pointed to by arg should be at least FMNAMESZ+1 bytes long.
This requires the declaration `#include <sys/conf.h>'. On
failure, errno is set to one of the following values:

EFAULT arg points outside the allocated address space.

EINVAL No module present in stream.

I_FLUSH This request flushes all input and/or output queues, depending
on the value of arg. Legal arg values are:

FLUSHR Flush read queues.

FLUSHW Flush write queues.

FLUSHRW Flush read and write queues.

If a pipe or FIFO does not have any modules pushed, the read
queue of the stream head on either end is flushed depending on
the value of arg.

If FLUSHR is set and fildes is a pipe, the read queue for that
end of the pipe is flushed and the write queue for the other
end is flushed. If fildes is a FIFO, both queues are flushed.

If FLUSHW is set and fildes is a pipe and the other end of the
pipe exists, the read queue for the other end of the pipe is
flushed and the write queue for this end is flushed. If
fildes is a FIFO, both queues of the FIFO are flushed.

If FLUSHRW is set, all read queues are flushed, that is, the
read queue for the FIFO and the read queue on both ends of the
pipe are flushed.

Correct flush handling of a pipe or FIFO with modules pushed
is achieved via the pipemod module. This module should be the
first module pushed onto a pipe so that it is at the midpoint
of the pipe itself.

On failure, errno is set to one of the following values:

ENOSR Unable to allocate buffers for flush message due to
insufficient stream memory resources.

EINVAL Invalid arg value.

ENXIO Hangup received on fildes.

I_FLUSHBAND Flushes a particular band of messages. arg points to a
bandinfo structure that has the following members:

unsigned char bi_pri;
int bi_flag;

The bi_flag field may be one of FLUSHR, FLUSHW, or FLUSHRW as
described earlier.

I_SETSIG Informs the stream head that the user wishes the kernel to
issue the SIGPOLL signal (see signal(3C)) when a particular
event has occurred on the stream associated with fildes.
I_SETSIG supports an asynchronous processing capability in
streams. The value of arg is a bitmask that specifies the
events for which the user should be signaled. It is the
bitwise OR of any combination of the following constants:

S_INPUT Any message other than an M_PCPROTO has arrived on
a stream head read queue. This event is maintained
for compatibility with previous releases. This
event is triggered even if the message is of zero
length.

S_RDNORM An ordinary (non-priority) message has arrived on a
stream head read queue. This event is triggered
even if the message is of zero length.

S_RDBAND A priority band message (band > 0) has arrived on a
stream head read queue. This event is triggered
even if the message is of zero length.

S_HIPRI A high priority message is present on the stream
head read queue. This event is triggered even if
the message is of zero length.

S_OUTPUT The write queue just below the stream head is no
longer full. This notifies the user that there is
room on the queue for sending (or writing) data
downstream.

S_WRNORM This event is the same as S_OUTPUT.

S_WRBAND A priority band greater than 0 of a queue
downstream exists and is writable. This notifies
the user that there is room on the queue for
sending (or writing) priority data downstream.

S_MSG A STREAMS signal message that contains the SIGPOLL
signal has reached the front of the stream head
read queue.

S_ERROR An M_ERROR message has reached the stream head.

S_HANGUP An M_HANGUP message has reached the stream head.

S_BANDURG When used in conjunction with S_RDBAND, SIGURG is
generated instead of SIGPOLL when a priority
message reaches the front of the stream head read
queue.

A user process may choose to be signaled only of high priority
messages by setting the arg bitmask to the value S_HIPRI.

Processes that wish to receive SIGPOLL signals must explicitly
register to receive them using I_SETSIG. If several processes
register to receive this signal for the same event on the same
stream, each process will be signaled when the event occurs.

If the value of arg is zero, the calling process will be
unregistered and will not receive further SIGPOLL signals. On
failure, errno is set to one of the following values:

EINVAL arg value is invalid or arg is zero and process is not
registered to receive the SIGPOLL signal.

EAGAIN Allocation of a data structure to store the signal
request failed.

I_GETSIG Returns the events for which the calling process is currently
registered to be sent a SIGPOLL signal. The events are
returned as a bitmask pointed to by arg, where the events are
those specified in the description of I_SETSIG above. On
failure, errno is set to one of the following values:

EINVAL Process not registered to receive the SIGPOLL signal.

EFAULT arg points outside the allocated address space.

I_FIND Compares the names of all modules currently present in the
stream to the name pointed to by arg, and returns 1 if the
named module is present in the stream. It returns 0 if the
named module is not present. On failure, errno is set to one
of the following values:

EFAULT arg points outside the allocated address space.

EINVAL arg does not contain a valid module name.

I_PEEK Allows a user to retrieve the information in the first message
on the stream head read queue without taking the message off
the queue. I_PEEK is analogous to getmsg(2) except that it
does not remove the message from the queue. arg points to a
strpeek structure, which contains the following members:

struct strbuf ctlbuf;
struct strbuf databuf;
long flags;

The maxlen field in the ctlbuf and databuf strbuf structures
(see getmsg(2)) must be set to the number of bytes of control
information and/or data information, respectively, to
retrieve. flags may be set to RS_HIPRI or 0. If RS_HIPRI is
set, I_PEEK will look for a high priority message on the
stream head read queue. Otherwise, I_PEEK will look for the
first message on the stream head read queue.

I_PEEK returns 1 if a message was retrieved, and returns 0 if
no message was found on the stream head read queue. It does
not wait for a message to arrive. On return, ctlbuf specifies
information in the control buffer, databuf specifies
information in the data buffer, and flags contains the value
RS_HIPRI or 0. On failure, errno is set to the following
value:

EFAULT arg points, or the buffer area specified in ctlbuf or
databuf is, outside the allocated address space.

EBADMSG Queued message to be read is not valid for I_PEEK.

EINVAL Illegal value for flags.

ENOSR Unable to allocate buffers to perform the I_PEEK due
to insufficient STREAMS memory resources.

I_SRDOPT Sets the read mode (see read(2)) using the value of the
argument arg. Legal arg values are:

RNORM Byte-stream mode, the default.

RMSGD Message-discard mode.

RMSGN Message-nondiscard mode.

In addition, the stream head's treatment of control messages
may be changed by setting the following flags in arg:

RPROTNORM Reject read(2) with EBADMSG if a control message is
at the front of the stream head read queue.

RPROTDAT Deliver the control portion of a message as data
when a user issues read(2). This is the default
behavior.

RPROTDIS Discard the control portion of a message,
delivering any data portion, when a user issues a
read(2).

On failure, errno is set to the following value:

EINVAL arg is not one of the above legal values, or arg is
the bitwise inclusive OR of RMSGD and RMSGN.

I_GRDOPT Returns the current read mode setting in an int pointed to by
the argument arg. Read modes are described in read(2). On
failure, errno is set to the following value:

EFAULT arg points outside the allocated address space.

I_NREAD Counts the number of data bytes in data blocks in the first
message on the stream head read queue, and places this value
in the location pointed to by arg. The return value for the
command is the number of messages on the stream head read
queue. For example, if zero is returned in arg, but the
ioctl() return value is greater than zero, this indicates that
a zero-length message is next on the queue. On failure, errno
is set to the following value:

EFAULT arg points outside the allocated address space.

I_FDINSERT Creates a message from specified buffer(s), adds information
about another stream and sends the message downstream. The
message contains a control part and an optional data part.
The data and control parts to be sent are distinguished by
placement in separate buffers, as described below.

The arg argument points to a strfdinsert structure, which
contains the following members:

struct strbuf ctlbuf;
struct strbuf databuf;
t_uscalar_t flags;
int fildes;
int offset;

The len member in the ctlbuf strbuf structure (see putmsg(2))
must be set to the size of a t_uscalar_t plus the number of
bytes of control information to be sent with the message. The
fildes member specifies the file descriptor of the other
stream, and the offset member, which must be suitably aligned
for use as a t_uscalar_t, specifies the offset from the start
of the control buffer where I_FDINSERT will store a
t_uscalar_t whose interpretation is specific to the stream
end. The len member in the databuf strbuf structure must be
set to the number of bytes of data information to be sent with
the message, or to 0 if no data part is to be sent.

The flags member specifies the type of message to be created.
A normal message is created if flags is set to 0, and a high-
priority message is created if flags is set to RS_HIPRI. For
non-priority messages, I_FDINSERT will block if the stream
write queue is full due to internal flow control conditions.
For priority messages, I_FDINSERT does not block on this
condition. or non-priority messages, I_FDINSERT does not
block when the write queue is full and O_NDELAY or O_NONBLOCK
is set. Instead, it fails and sets errno to EAGAIN.

I_FDINSERT also blocks, unless prevented by lack of internal
resources, waiting for the availability of message blocks in
the stream, regardless of priority or whether O_NDELAY or
O_NONBLOCK has been specified. No partial message is sent.

The ioctl() function with the I_FDINSERT command will fail if:

EAGAIN A non-priority message is specified, the O_NDELAY or
O_NONBLOCK flag is set, and the stream write queue is
full due to internal flow control conditions.

ENOSR Buffers can not be allocated for the message that is
to be created.

EFAULT The arg argument points, or the buffer area specified
in ctlbuf or databuf is, outside the allocated address
space.

EINVAL One of the following: The fildes member of the
strfdinsert structure is not a valid, open stream file
descriptor; the size of a t_uscalar_t plus offset is
greater than the len member for the buffer specified
through ctlptr; the offset member does not specify a
properly-aligned location in the data buffer; or an
undefined value is stored in flags.

ENXIO Hangup received on the fildes argument of the ioctl()
call or the fildes member of the strfdinsert
structure.

ERANGE The len field for the buffer specified through databuf
does not fall within the range specified by the
maximum and minimum packet sizes of the topmost stream
module; or the len member for the buffer specified
through databuf is larger than the maximum configured
size of the data part of a message; or the len member
for the buffer specified through ctlbuf is larger than
the maximum configured size of the control part of a
message.

I_FDINSERT can also fail if an error message was received by
the stream head of the stream corresponding to the fildes
member of the strfdinsert structure. In this case, errno will
be set to the value in the message.

I_STR Constructs an internal STREAMS ioctl message from the data
pointed to by arg, and sends that message downstream.

This mechanism is provided to send user ioctl() requests to
downstream modules and drivers. It allows information to be
sent with the ioctl(), and will return to the user any
information sent upstream by the downstream recipient. I_STR
blocks until the system responds with either a positive or
negative acknowledgement message, or until the request times
out after some period of time. If the request times out, it
fails with errno set to ETIME.

To send requests downstream, arg must point to a strioctl
structure which contains the following members:

int ic_cmd;
int ic_timout;
int ic_len;
char *ic_dp;

ic_cmd is the internal ioctl() command intended for a
downstream module or driver and ic_timout is the number of
seconds (-1 = infinite, 0 = use default, >0 = as specified) an
I_STR request will wait for acknowledgement before timing out.
ic_len is the number of bytes in the data argument and ic_dp
is a pointer to the data argument. The ic_len field has two
uses: on input, it contains the length of the data argument
passed in, and on return from the command, it contains the
number of bytes being returned to the user (the buffer pointed
to by ic_dp should be large enough to contain the maximum
amount of data that any module or the driver in the stream can
return).

At most one I_STR can be active on a stream. Further I_STR
calls will block until the active I_STR completes via a
positive or negative acknowledgement, a timeout, or an error
condition at the stream head. By setting the ic_timout field
to 0, the user is requesting STREAMS to provide the DEFAULT
timeout. The default timeout is specific to the STREAMS
implementation and may vary depending on which release of
Solaris you are using. For Solaris 8 (and earlier versions),
the default timeout is fifteen seconds. The O_NDELAY and
O_NONBLOCK (see open(2)) flags have no effect on this call.

The stream head will convert the information pointed to by the
strioctl structure to an internal ioctl() command message and
send it downstream. On failure, errno is set to one of the
following values:

ENOSR Unable to allocate buffers for the ioctl() message due
to insufficient STREAMS memory resources.

EFAULT Either arg points outside the allocated address space,
or the buffer area specified by ic_dp and ic_len
(separately for data sent and data returned) is
outside the allocated address space.

EINVAL ic_len is less than 0 or ic_len is larger than the
maximum configured size of the data part of a message
or ic_timout is less than -1.

ENXIO Hangup received on fildes.

ETIME A downstream ioctl() timed out before acknowledgement
was received.

An I_STR can also fail while waiting for an acknowledgement if
a message indicating an error or a hangup is received at the
stream head. In addition, an error code can be returned in
the positive or negative acknowledgement message, in the event
the ioctl command sent downstream fails. For these cases,
I_STR will fail with errno set to the value in the message.

I_SWROPT Sets the write mode using the value of the argument arg.
Legal bit settings for arg are:

SNDZERO Send a zero-length message downstream when a write of
0 bytes occurs.

To not send a zero-length message when a write of 0 bytes
occurs, this bit must not be set in arg.

On failure, errno may be set to the following value:

EINVAL arg is not the above legal value.

I_GWROPT Returns the current write mode setting, as described above, in
the int that is pointed to by the argument arg.

I_SENDFD Requests the stream associated with fildes to send a message,
containing a file pointer, to the stream head at the other end
of a stream pipe. The file pointer corresponds to arg, which
must be an open file descriptor.

I_SENDFD converts arg into the corresponding system file
pointer. It allocates a message block and inserts the file
pointer in the block. The user id and group id associated
with the sending process are also inserted. This message is
placed directly on the read queue (see Intro(3)) of the stream
head at the other end of the stream pipe to which it is
connected. On failure, errno is set to one of the following
values:

EAGAIN The sending stream is unable to allocate a message
block to contain the file pointer.

EAGAIN The read queue of the receiving stream head is full
and cannot accept the message sent by I_SENDFD.

EBADF arg is not a valid, open file descriptor.

EINVAL fildes is not connected to a stream pipe.

ENXIO Hangup received on fildes.

I_RECVFD Retrieves the file descriptor associated with the message sent
by an I_SENDFD ioctl() over a stream pipe. arg is a pointer
to a data buffer large enough to hold an strrecvfd data
structure containing the following members:

int fd;
uid_t uid;
gid_t gid;

fd is an integer file descriptor. uid and gid are the user id
and group id, respectively, of the sending stream.

If O_NDELAY and O_NONBLOCK are clear (see open(2)), I_RECVFD
will block until a message is present at the stream head. If
O_NDELAY or O_NONBLOCK is set, I_RECVFD will fail with errno
set to EAGAIN if no message is present at the stream head.

If the message at the stream head is a message sent by an
I_SENDFD, a new user file descriptor is allocated for the file
pointer contained in the message. The new file descriptor is
placed in the fd field of the strrecvfd structure. The
structure is copied into the user data buffer pointed to by
arg. On failure, errno is set to one of the following values:

EAGAIN A message is not present at the stream head read
queue, and the O_NDELAY or O_NONBLOCK flag is set.

EBADMSG The message at the stream head read queue is not a
message containing a passed file descriptor.

EFAULT arg points outside the allocated address space.

EMFILE NOFILES file descriptors are currently open.

ENXIO Hangup received on fildes.

EOVERFLOW uid or gid is too large to be stored in the
structure pointed to by arg.

I_LIST Allows the user to list all the module names on the stream, up
to and including the topmost driver name. If arg is NULL, the
return value is the number of modules, including the driver,
that are on the stream pointed to by fildes. This allows the
user to allocate enough space for the module names. If arg is
non-null, it should point to an str_list structure that has
the following members:

int sl_nmods;
struct str_mlist *sl_modlist;

The str_mlist structure has the following member:

char l_name[FMNAMESZ+1];

The sl_nmods member indicates the number of entries the
process has allocated in the array. Upon return, the
sl_modlist member of the str_list structure contains the list
of module names, and the number of entries that have been
filled into the sl_modlist array is found in the sl_nmods
member (the number includes the number of modules including
the driver). The return value from ioctl() is 0. The entries
are filled in starting at the top of the stream and continuing
downstream until either the end of the stream is reached, or
the number of requested modules (sl_nmods) is satisfied. On
failure, errno may be set to one of the following values:

EINVAL The sl_nmods member is less than 1.

EAGAIN Unable to allocate buffers

I_ATMARK Allows the user to see if the current message on the stream
head read queue is "marked" by some module downstream. arg
determines how the checking is done when there may be multiple
marked messages on the stream head read queue. It may take
the following values:

ANYMARK Check if the message is marked.

LASTMARK Check if the message is the last one marked on the
queue.

The return value is 1 if the mark condition is satisfied and 0
otherwise. On failure, errno is set to the following value:

EINVAL Invalid arg value.

I_CKBAND Check if the message of a given priority band exists on the
stream head read queue. This returns 1 if a message of a
given priority exists, 0 if not, or -1 on error. arg should
be an integer containing the value of the priority band in
question. On failure, errno is set to the following value:

EINVAL Invalid arg value.

I_GETBAND Returns the priority band of the first message on the stream
head read queue in the integer referenced by arg. On failure,
errno is set to the following value:

ENODATA No message on the stream head read queue.

I_CANPUT Check if a certain band is writable. arg is set to the
priority band in question. The return value is 0 if the
priority band arg is flow controlled, 1 if the band is
writable, or -1 on error. On failure, errno is set to the
following value:

EINVAL Invalid arg value.

I_SETCLTIME Allows the user to set the time the stream head will delay
when a stream is closing and there are data on the write
queues. Before closing each module and driver, the stream
head will delay for the specified amount of time to allow the
data to drain. Note, however, that the module or driver may
itself delay in its close routine; this delay is independent
of the stream head's delay and is not settable. If, after the
delay, data are still present, data will be flushed. arg is a
pointer to an integer containing the number of milliseconds to
delay, rounded up to the nearest legal value on the system.
The default is fifteen seconds. On failure, errno is set to
the following value:

EINVAL Invalid arg value.

I_GETCLTIME Returns the close time delay in the integer pointed by arg.

I_SERROPT Sets the error mode using the value of the argument arg.

Normally stream head errors are persistent; once they are set
due to an M_ERROR or M_HANGUP, the error condition will remain
until the stream is closed. This option can be used to set
the stream head into non-persistent error mode i.e. once the
error has been returned in response to a read(2), getmsg(2),
ioctl(2), write(2), or putmsg(2) call the error condition will
be cleared. The error mode can be controlled independently
for read and write side errors. Legal arg values are either
none or one of:

RERRNORM Persistent read errors, the default.

RERRNONPERSIST Non-persistent read errors.

OR'ed with either none or one of:

WERRNORM Persistent write errors, the default.

WERRNONPERSIST Non-persistent write errors.

When no value is specified e.g. for the read side error
behavior then the behavior for that side will be left
unchanged.

On failure, errno is set to the following value:

EINVAL arg is not one of the above legal values.

I_GERROPT Returns the current error mode setting in an int pointed to by
the argument arg. Error modes are described above for
I_SERROPT. On failure, errno is set to the following value:

EFAULT arg points outside the allocated address space.

The following four commands are used for connecting and disconnecting
multiplexed STREAMS configurations.

I_LINK Connects two streams, where fildes is the file descriptor of the
stream connected to the multiplexing driver, and arg is the file
descriptor of the stream connected to another driver. The
stream designated by arg gets connected below the multiplexing
driver. I_LINK requires the multiplexing driver to send an
acknowledgement message to the stream head regarding the linking
operation. This call returns a multiplexor ID number (an
identifier used to disconnect the multiplexor, see I_UNLINK) on
success, and -1 on failure. On failure, errno is set to one of
the following values:

ENXIO Hangup received on fildes.

ETIME Time out before acknowledgement message was received at
stream head.

EAGAIN Temporarily unable to allocate storage to perform the
I_LINK.

ENOSR Unable to allocate storage to perform the I_LINK due to
insufficient STREAMS memory resources.

EBADF arg is not a valid, open file descriptor.

EINVAL fildes stream does not support multiplexing.

EINVAL is not a stream, or is already linked under a
multiplexor.

EINVAL The specified link operation would cause a "cycle" in
the resulting configuration; that is, a driver would be
linked into the multiplexing configuration in more than
one place.

EINVAL fildes is the file descriptor of a pipe or FIFO.

EINVAL Either the upper or lower stream has a major number >=
the maximum major number on the system.

An I_LINK can also fail while waiting for the multiplexing
driver to acknowledge the link request, if a message indicating
an error or a hangup is received at the stream head of fildes.
In addition, an error code can be returned in the positive or
negative acknowledgement message. For these cases, I_LINK will
fail with errno set to the value in the message.

I_UNLINK Disconnects the two streams specified by fildes and arg. fildes
is the file descriptor of the stream connected to the
multiplexing driver. arg is the multiplexor ID number that was
returned by the I_LINK. If arg is -1, then all streams that
were linked to fildes are disconnected. As in I_LINK, this
command requires the multiplexing driver to acknowledge the
unlink. On failure, errno is set to one of the following
values:

ENXIO Hangup received on fildes.

ETIME Time out before acknowledgement message was received at
stream head.

ENOSR Unable to allocate storage to perform the I_UNLINK due
to insufficient STREAMS memory resources.

EINVAL arg is an invalid multiplexor ID number or fildes is not
the stream on which the I_LINK that returned arg was
performed.

EINVAL fildes is the file descriptor of a pipe or FIFO.

An I_UNLINK can also fail while waiting for the multiplexing
driver to acknowledge the link request, if a message indicating
an error or a hangup is received at the stream head of fildes.
In addition, an error code can be returned in the positive or
negative acknowledgement message. For these cases, I_UNLINK
will fail with errno set to the value in the message.

I_PLINK Connects two streams, where fildes is the file descriptor of the
stream connected to the multiplexing driver, and arg is the file
descriptor of the stream connected to another driver. The
stream designated by arg gets connected via a persistent link
below the multiplexing driver. I_PLINK requires the
multiplexing driver to send an acknowledgement message to the
stream head regarding the linking operation. This call creates
a persistent link that continues to exist even if the file
descriptor fildes associated with the upper stream to the
multiplexing driver is closed. This call returns a multiplexor
ID number (an identifier that may be used to disconnect the
multiplexor, see I_PUNLINK) on success, and -1 on failure. On
failure, errno is set to one of the following values:

ENXIO Hangup received on fildes.

ETIME Time out before acknowledgement message was received at
the stream head.

EAGAIN Unable to allocate STREAMS storage to perform the
I_PLINK.

EBADF arg is not a valid, open file descriptor.

EINVAL fildes does not support multiplexing.

EINVAL arg is not a stream or is already linked under a
multiplexor.

EINVAL The specified link operation would cause a "cycle" in
the resulting configuration; that is, if a driver would
be linked into the multiplexing configuration in more
than one place.

EINVAL fildes is the file descriptor of a pipe or FIFO.

An I_PLINK can also fail while waiting for the multiplexing
driver to acknowledge the link request, if a message indicating
an error on a hangup is received at the stream head of fildes.
In addition, an error code can be returned in the positive or
negative acknowledgement message. For these cases, I_PLINK will
fail with errno set to the value in the message.

I_PUNLINK Disconnects the two streams specified by fildes and arg that are
connected with a persistent link. fildes is the file descriptor
of the stream connected to the multiplexing driver. arg is the
multiplexor ID number that was returned by I_PLINK when a stream
was linked below the multiplexing driver. If arg is MUXID_ALL
then all streams that are persistent links to fildes are
disconnected. As in I_PLINK, this command requires the
multiplexing driver to acknowledge the unlink. On failure,
errno is set to one of the following values:

ENXIO Hangup received on fildes.

ETIME Time out before acknowledgement message was received at
the stream head.

EAGAIN Unable to allocate buffers for the acknowledgement
message.

EINVAL Invalid multiplexor ID number.

EINVAL fildes is the file descriptor of a pipe or FIFO.

An I_PUNLINK can also fail while waiting for the multiplexing
driver to acknowledge the link request if a message indicating
an error or a hangup is received at the stream head of fildes.
In addition, an error code can be returned in the positive or
negative acknowledgement message. For these cases, I_PUNLINK
will fail with errno set to the value in the message.

RETURN VALUES

Unless specified otherwise above, the return value from ioctl(2) is 0 upon
success and -1 upon failure, with errno set as indicated.

SEE ALSO

close(2), fcntl(2), getmsg(2), ioctl(2), open(2), poll(2), putmsg(2),
read(2), write(2), Intro(3), signal(3C), signal.h(3HEAD)

STREAMS Programming Guide

illumos March 13, 2022 illumos