_io_connect

Structure of a resource manager's connect message

Synopsis:

struct _io_connect {
    uint16_t                type;
    uint16_t                subtype;
    uint32_t                file_type;
    uint16_t                reply_max;
    uint16_t                entry_max;
    uint32_t                key;
    uint32_t                handle;
    uint32_t                ioflag;
    uint32_t                mode;
    uint16_t                sflag;
    uint16_t                access;
    uint16_t                zero;
    uint16_t                path_len;
    uint8_t                 eflag;
    uint8_t                 extra_type;
    uint16_t                extra_len;
    char                    path[1];
};

Description:

The _io_connect structure is used to describe a connect message that a resource manager receives and sends.

The members include:

type

_IO_CONNECT

subtype

The type of connection that the message concerns; one of:

• _IO_CONNECT_COMBINE — combine with an I/O message.
• _IO_CONNECT_COMBINE_CLOSE — combine with I/O message and always close.
• _IO_CONNECT_OPEN
• _IO_CONNECT_UNLINK
• _IO_CONNECT_RENAME
• _IO_CONNECT_MKNOD
• _IO_CONNECT_READLINK
• _IO_CONNECT_LINK
• _IO_CONNECT_RSVD_UNBLOCK — place holder in the jump table.
• _IO_CONNECT_MOUNT

file_type

The file type; one of the following (defined in <sys/ftype.h>):

• _FTYPE_ANY — the path name can be anything.
• _FTYPE_LINK — reserved for the Process Manager.
• _FTYPE_MOUNT — receive mount requests on the path (path must be NULL).
• _FTYPE_MQUEUE — reserved for a message-queue manager.
• _FTYPE_PIPE — reserved for a pipe manager.
• _FTYPE_SEM — reserved for a semaphore manager.
• _FTYPE_SHMEM — reserved for a shared memory object.
• _FTYPE_SOCKET — reserved for a socket manager.
• _FTYPE_SYMLINK — reserved for the Process Manager.

reply_max

The maximum length of the reply message.

entry_max

The maximum number of _io_connect_entry structures that the resource manager is willing to accept. If a path could reference more than one resource manager, it returns a list of _io_connect_entry structures referring to the overlapping resource managers.

key

Reserved.

handle

The handle returned by resmgr_attach().

ioflag

The bottom two bits are modified from traditional Unix values to more useful bit flags:

• O_RDONLY (0) is converted to _IO_FLAG_RD (0x01)
• O_WRONLY (1) is converted to _IO_FLAG_WR (0x02)
• O_RDWR (2) is converted to _IO_FLAG_RD | _IO_FLAG_WR (0x03)

Note that this translation can be performed without overlapping other O_* flags.

To check for permissions, use the following:

• ioflag & _IO_FLAG_RD for read permission
• ioflag & _IO_FLAG_WR for write permission
• If the file is open for reading and writing, both bits are set.

The remaining values of ioflag are outside this range and are not modified. These values are:

• O_APPEND — if set, the file offset is set to the end of the file prior to each write.
• O_CREAT — create the file.
• O_DSYNC — if set, this flag affects subsequent I/O calls; each call to write() waits until all data is successfully transferred to the storage device such that it's readable on any subsequent open of the file (even one that follows a system failure) in the absence of a failure of the physical storage medium. If the physical storage medium implements a non-write-through cache, then a system failure may be interpreted as a failure of the physical storage medium, and data may not be readable even if this flag is set and the write() indicates that it succeeded.
• O_EXCL — if you set both O_EXCL and O_CREAT, open() fails if the file exists. The check for the existence of the file and the creation of the file if it doesn't exist are atomic; no other process that's attempting the same operation with the same filename at the same time will succeed. Specifying O_EXCL without O_CREAT has no effect.
• O_LARGEFILE — allow the file offset to be 64 bits long.
• O_NOCTTY — if set, and path identifies a terminal device, the open() function doesn't cause the terminal device to become the controlling terminal for the process.
• O_NONBLOCK — don't block.
• O_REALIDS — use the real uid/gid for permissions checking.
• O_RSYNC — read I/O operations on the file descriptor complete at the same level of integrity as specified by the O_DSYNC and O_SYNC flags.
• O_SYNC — if set, this flag affects subsequent I/O calls; each call to read() or write() is complete only when both the data has been successfully transferred (either read or written) and all file system information relevant to that I/O operation (including that required to retrieve said data) is successfully transferred, including file update and/or access times, and so on. See the discussion of a successful data transfer in O_DSYNC, above.
• O_TRUNC — if the file exists and is a regular file, and the file is successfully opened O_WRONLY or O_RDWR, the file length is truncated to zero and the mode and owner are left unchanged. O_TRUNC has no effect on FIFO or block or character special files or directories. Using O_TRUNC with O_RDONLY has no effect.

mode

Contains the type and access permissions of the file.

The type is one of:

• S_IFBLK — block special.
• S_IFCHR — character special.
• S_IFDIR — directory.
• S_IFIFO — FIFO special.
• S_IFLNK — symbolic link.
• S_IFMT — type of file.
• S_IFNAM — special named file.
• S_IFREG — regular.
• S_IFSOCK — socket.

The permissions are a combination of:

Owner	Group	Others	Permission
S_IRUSR	S_IRGRP	S_IROTH	Read
S_IRWXU	S_IRWXG	S_IRWXO	Read, write, execute/search. A bitwise inclusive OR of the other three constants (S_IRWXU is OR of IRUSR, S_IWSUR and S_IXUSR.)
S_IWUSR	S_IWGRP	S_IWOTH	Write
S_IXUSR	S_IXGRP	S_IXOTH	Execute/search

The following bits define miscellaneous permissions used by other implementations:

Bit	Equivalent
S_IEXEC	S_IXUSR
S_IREAD	S_IRUSR
S_IWRITE	S_IWUSR

sflag

How the client wants the file to be shared; a combination of the following bits:

• SH_COMPAT — set compatibility mode.
• SH_DENYRW — prevent read or write access to the file.
• SH_DENYWR — prevent write access to the file.
• SH_DENYRD — prevent read access to the file.
• SH_DENYNO — permit both read and write access to the file.

access

Contains a combination of _IO_FLAG_RD and _IO_FLAG_WR bits, which are used internally as the access permissions to allow from ioflag.

path_len

The length of the path member.

eflag

Extended flags:

• _IO_CONNECT_EFLAG_DIR — the path referenced a directory.
• _IO_CONNECT_EFLAG_DOT — the last component of a path was . or .. (i.e. the current or parent directory).

extra_type

One of:

• _IO_CONNECT_EXTRA_NONE
• _IO_CONNECT_EXTRA_LINK
• _IO_CONNECT_EXTRA_SYMLINK
• _IO_CONNECT_EXTRA_MQUEUE
• _IO_CONNECT_EXTRA_PHOTON
• _IO_CONNECT_EXTRA_SOCKET
• _IO_CONNECT_EXTRA_SEM
• _IO_CONNECT_EXTRA_RESMGR_LINK
• _IO_CONNECT_EXTRA_PROC_SYMLINK
• _IO_CONNECT_EXTRA_RENAME
• _IO_CONNECT_EXTRA_MOUNT
• _IO_CONNECT_EXTRA_MOUNT_OCB

extra_len

The length of any extra data included in the message.

path

The path that the client is trying to connect to, relative to the resource manager's mountpoint.

Classification:

QNX Neutrino

See also:

_io_connect_ftype_reply, _io_connect_link_reply, resmgr_connect_funcs_t

“The _IO_OPEN message for filesystems” in the Filesystem Resource Managers chapter of Writing a Resource Manager