minix/servers/pfs/dev_uds.c

/*
 * Unix Domain Sockets Implementation (PF_UNIX, PF_LOCAL)
 * This code handles requests generated by operations on /dev/uds
 *
 * The entry points into this file are...
 *
 *   uds_request: process a character device request
 *
 * Also See...
 *
 *   uds.c, uds.h
 *
 * Overview
 *
 * The interface to unix domain sockets is similar to the interface to network
 * sockets. There is a character device (/dev/uds) and this server is a
 * 'driver' for that device.
 */

#define DEBUG 0

#include "inc.h"
#include "const.h"
#include "glo.h"
#include "uds.h"

static ssize_t uds_perform_read(devminor_t minor, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int pretend);
static ssize_t uds_perform_write(devminor_t minor, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int pretend);

static int uds_open(devminor_t orig_minor, int access, endpoint_t user_endpt);
static int uds_close(devminor_t minor);
static ssize_t uds_read(devminor_t minor, u64_t position, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int flags, cdev_id_t id);
static ssize_t uds_write(devminor_t minor, u64_t position, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int flags, cdev_id_t id);
static int uds_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
	cp_grant_id_t grant, int flags, endpoint_t user_endpt, cdev_id_t id);
static int uds_cancel(devminor_t minor, endpoint_t endpt, cdev_id_t id);
static int uds_select(devminor_t minor, unsigned int ops, endpoint_t endpt);

static struct chardriver uds_tab = {
	.cdr_open	= uds_open,
	.cdr_close	= uds_close,
	.cdr_read	= uds_read,
	.cdr_write	= uds_write,
	.cdr_ioctl	= uds_ioctl,
	.cdr_cancel	= uds_cancel,
	.cdr_select	= uds_select
};

void uds_request(message *m_ptr, int ipc_status)
{
	/* Use libchardriver to process character device requests. */
	chardriver_process(&uds_tab, m_ptr, ipc_status);
}

static int uds_open(devminor_t UNUSED(orig_minor), int access,
	endpoint_t user_endpt)
{
	message fs_m_in, fs_m_out;
	struct uucred ucred;
	devminor_t minor;
	int rc, i;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [-] uds_open() call_count=%d\n", ++call_count);
	printf("Endpoint: 0x%x\n", user_endpt);
#endif

	/*
	 * Find a slot in the descriptor table for the new descriptor.
	 * The index of the descriptor in the table will be returned.
	 * Subsequent calls to read/write/close/ioctl/etc will use this
	 * minor number. The minor number must be different from the
	 * the /dev/uds device's minor number (currently 0).
	 */

	minor = -1; /* to trap error */

	for (i = 1; i < NR_FDS; i++) {
		if (uds_fd_table[i].state == UDS_FREE) {
			minor = i;
			break;
		}
	}

	if (minor == -1)
		return ENFILE;

	/*
	 * We found a slot in uds_fd_table, now initialize the descriptor
	 */

	/* mark this one as 'in use' so that it doesn't get assigned to
	 * another socket
	 */
	uds_fd_table[minor].state = UDS_INUSE;

	/* set the socket owner */
	uds_fd_table[minor].owner = user_endpt;

	/* setup select(2) framework */
	uds_fd_table[minor].sel_endpt = NONE;
	uds_fd_table[minor].sel_ops = 0;

	/* initialize the data pointer (pos) to the start of the PIPE */
	uds_fd_table[minor].pos = 0;

	/* the PIPE is initially empty */
	uds_fd_table[minor].size = 0;

	/* the default for a new socket is to allow reading and writing.
	 * shutdown(2) will remove one or both flags.
	 */
	uds_fd_table[minor].mode = S_IRUSR|S_IWUSR;

	/* In libc socket(2) sets this to the actual value later with the
	 * NWIOSUDSTYPE ioctl().
	 */
	uds_fd_table[minor].type = -1;

	/* Clear the backlog by setting each entry to -1 */
	for (i = 0; i < UDS_SOMAXCONN; i++) {
		/* initially no connections are pending */
		uds_fd_table[minor].backlog[i] = -1;
	}

	memset(&uds_fd_table[minor].ancillary_data, '\0', sizeof(struct
								ancillary));
	for (i = 0; i < OPEN_MAX; i++) {
		uds_fd_table[minor].ancillary_data.fds[i] = -1;
	}

	/* default the size to UDS_SOMAXCONN */
	uds_fd_table[minor].backlog_size = UDS_SOMAXCONN;

	/* the socket isn't listening for incoming connections until
	 * listen(2) is called
	 */
	uds_fd_table[minor].listening = 0;

	/* initially the socket is not connected to a peer */
	uds_fd_table[minor].peer = -1;

	/* there isn't a child waiting to be accept(2)'d */
	uds_fd_table[minor].child = -1;

	/* initially the socket is not bound or listening on an address */
	memset(&(uds_fd_table[minor].addr), '\0', sizeof(struct sockaddr_un));
	memset(&(uds_fd_table[minor].source), '\0', sizeof(struct sockaddr_un));
	memset(&(uds_fd_table[minor].target), '\0', sizeof(struct sockaddr_un));

	/* Initially the socket isn't suspended. */
	uds_fd_table[minor].suspended = UDS_NOT_SUSPENDED;

	/* get the effective user id and effective group id from the endpoint */
	/* this is needed in the REQ_NEWNODE request to PFS. */
	rc = getnucred(user_endpt, &ucred);
	if (rc == -1) {
		/* roll back the changes we made to the descriptor */
		memset(&(uds_fd_table[minor]), '\0', sizeof(uds_fd_t));

		/* likely error: invalid endpoint / proc doesn't exist */
		return EIO;
	}

	/* Prepare Request to the FS side of PFS */

	fs_m_in.m_type = REQ_NEWNODE;
	fs_m_in.REQ_MODE = I_NAMED_PIPE;
	fs_m_in.REQ_DEV = NO_DEV;
	fs_m_in.REQ_UID = ucred.cr_uid;
	fs_m_in.REQ_GID = ucred.cr_gid;

	/* Request a new inode on the pipe file system */

	rc = fs_newnode(&fs_m_in, &fs_m_out);
	if (rc != OK) {
		/* roll back the changes we made to the descriptor */
		memset(&(uds_fd_table[minor]), '\0', sizeof(uds_fd_t));

		/* likely error: get_block() failed */
		return rc;
	}

	/* Process the response */
	uds_fd_table[minor].inode_nr = fs_m_out.RES_INODE_NR;

	return CDEV_CLONED | minor;
}

static int uds_close(devminor_t minor)
{
	message fs_m_in, fs_m_out;
	int rc;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_close() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return ENXIO;

	if (uds_fd_table[minor].state != UDS_INUSE) {
		/* attempted to close a socket that hasn't been opened --
		 * something is very wrong :(
		 */
		return EINVAL;
	}

	/* if the socket is connected, disconnect it */
	if (uds_fd_table[minor].peer != -1) {
		int peer = uds_fd_table[minor].peer;

		/* set peer of this peer to -1 */
		uds_fd_table[peer].peer = -1;

		/* error to pass to peer */
		uds_fd_table[peer].err = ECONNRESET;

		/* if peer was blocked on I/O revive peer */
		if (uds_fd_table[peer].suspended != UDS_NOT_SUSPENDED)
			uds_unsuspend(peer);
	}

	if (uds_fd_table[minor].ancillary_data.nfiledes > 0) {
		uds_clear_fds(minor, &uds_fd_table[minor].ancillary_data);
	}

	/* Prepare Request to the FS side of PFS */

	fs_m_in.m_type = REQ_PUTNODE;
	fs_m_in.REQ_INODE_NR = uds_fd_table[minor].inode_nr;
	fs_m_in.REQ_COUNT = 1;

	/* set the socket back to its original UDS_FREE state */
	memset(&(uds_fd_table[minor]), '\0', sizeof(uds_fd_t));

	/* Request the removal of the inode from the pipe file system */

	rc = fs_putnode(&fs_m_in, &fs_m_out);
	if (rc != OK) {
		printf("PFS: fs_putnode returned %d\n", rc);

		return rc;
	}

	return OK;
}

static int uds_select(devminor_t minor, unsigned int ops, endpoint_t endpt)
{
	unsigned int ready_ops;
	int i, bytes, watch;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_select() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return ENXIO;

	if (uds_fd_table[minor].state != UDS_INUSE) {
		/* attempted to select on a socket that hasn't been opened --
		 * something is very wrong :(
		 */
		return EINVAL;
	}

	watch = (ops & CDEV_NOTIFY);
	ops &= (CDEV_OP_RD | CDEV_OP_WR | CDEV_OP_ERR);

	ready_ops = 0;

	/* check if there is data available to read */
	if (ops & CDEV_OP_RD) {
		bytes = uds_perform_read(minor, NONE, GRANT_INVALID, 1, 1);
		if (bytes > 0) {
			/* there is data in the pipe for us to read */
			ready_ops |= CDEV_OP_RD;
		} else if (uds_fd_table[minor].listening == 1) {
			/* check for pending connections */
			for (i = 0; i < uds_fd_table[minor].backlog_size; i++)
			{
				if (uds_fd_table[minor].backlog[i] != -1) {
					ready_ops |= CDEV_OP_RD;
					break;
				}
			}
		} else if (bytes != SUSPEND) {
			ready_ops |= CDEV_OP_RD;
		}
	}

	/* check if we can write without blocking */
	if (ops & CDEV_OP_WR) {
		bytes = uds_perform_write(minor, NONE, GRANT_INVALID, PIPE_BUF,
			1);
		if (bytes != 0 && bytes != SUSPEND) {
			/* There is room to write or there is an error
			 * condition.
			 */
			ready_ops |= CDEV_OP_WR;
		}
	}

	/* If not all requested ops were ready, and the caller requests to be
	 * notified about changes, we add the remaining ops to the saved set.
	 */
	ops &= ~ready_ops;
	if (ops && watch) {
		uds_fd_table[minor].sel_endpt = endpt;
		uds_fd_table[minor].sel_ops |= ops;
	}

	return ready_ops;
}

static ssize_t uds_perform_read(devminor_t minor, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int pretend)
{
	int rc, peer;
	message fs_m_in;
	message fs_m_out;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_perform_read() call_count=%d\n", minor,
							++call_count);
#endif

	peer = uds_fd_table[minor].peer;

	/* skip reads and writes of 0 (or less!) bytes */
	if (size <= 0) {
		return 0;
	}

	/* check if we are allowed to read */
	if (!(uds_fd_table[minor].mode & S_IRUSR)) {
		/* socket is shutdown for reading */
		return EPIPE;
	}

	if (uds_fd_table[minor].size == 0) {
		if (peer == -1) {
			/* We're not connected. That's only a problem when this
			 * socket is connection oriented. */
			if (uds_fd_table[minor].type == SOCK_STREAM ||
			    uds_fd_table[minor].type == SOCK_SEQPACKET) {
				if (uds_fd_table[minor].err == ECONNRESET) {
					uds_fd_table[minor].err = 0;
					return ECONNRESET;
				} else {
					return ENOTCONN;
				}
			}
		}

		/* Check if process is reading from a closed pipe */
		if (peer != -1 && !(uds_fd_table[peer].mode & S_IWUSR) &&
			uds_fd_table[minor].size == 0) {
			return 0;
		}

		if (pretend) {
			return SUSPEND;
		}

		/* maybe a process is blocked waiting to write? if
		 * needed revive the writer
		 */
		if (peer != -1 &&
			uds_fd_table[peer].suspended == UDS_SUSPENDED_WRITE)
			uds_unsuspend(peer);

#if DEBUG == 1
		printf("(uds) [%d] suspending read request\n", minor);
#endif
		/* Process is reading from an empty pipe,
		 * suspend it so some bytes can be written
		 */
		return EDONTREPLY;
	}

	if (pretend) {
		return (size > uds_fd_table[minor].size) ?
				uds_fd_table[minor].size : size;
	}

	/* Prepare Request to the FS side of PFS */
	fs_m_in.m_source = endpt;
	fs_m_in.m_type = REQ_READ;
	fs_m_in.REQ_INODE_NR = uds_fd_table[minor].inode_nr;
	fs_m_in.REQ_GRANT = grant;
	fs_m_in.REQ_SEEK_POS_HI = 0;
	fs_m_in.REQ_SEEK_POS_LO = uds_fd_table[minor].pos;
	fs_m_in.REQ_NBYTES = (size > uds_fd_table[minor].size) ?
				uds_fd_table[minor].size : size;

	/* perform the read */
	rc = fs_readwrite(&fs_m_in, &fs_m_out);
	if (rc != OK) {
		printf("PFS: fs_readwrite returned %d\n", rc);
		return rc;
	}

	/* Process the response */
#if DEBUG == 1
	printf("(uds) [%d] read complete\n", minor);
#endif

	/* move the position of the data pointer up to data we haven't
	 * read yet
	 */
	uds_fd_table[minor].pos += fs_m_out.RES_NBYTES;

	/* decrease the number of unread bytes */
	uds_fd_table[minor].size -= fs_m_out.RES_NBYTES;

	/* if we have 0 unread bytes, move the data pointer back to the
	 * start of the buffer
	 */
	if (uds_fd_table[minor].size == 0) {
		uds_fd_table[minor].pos = 0;
	}

	/* maybe a big write was waiting for us to read some data, if
	 * needed revive the writer
	 */
	if (peer != -1 && uds_fd_table[peer].suspended == UDS_SUSPENDED_WRITE)
		uds_unsuspend(peer);

	/* see if peer is blocked on select() and a write is possible (from
	 * peer to minor); if the peer wants to know about write being possible
	 * and it doesn't know about it already, then let the peer know.
	 */
	if (peer != -1 && (uds_fd_table[peer].sel_ops & CDEV_OP_WR) &&
	    (uds_fd_table[minor].size+uds_fd_table[minor].pos + 1 < PIPE_BUF)){
		/* a write on peer is possible now */
		chardriver_reply_select(uds_fd_table[peer].sel_endpt, peer,
			CDEV_OP_WR);
		uds_fd_table[peer].sel_ops &= ~CDEV_OP_WR;
	}

	return fs_m_out.RES_NBYTES; /* return number of bytes read */
}

static ssize_t uds_perform_write(devminor_t minor, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int pretend)
{
	int rc, peer, i;
	message fs_m_in;
	message fs_m_out;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_perform_write() call_count=%d\n", minor,
							++call_count);
#endif

	/* skip reads and writes of 0 (or less!) bytes */
	if (size <= 0) {
		return 0;
	}

	/* check if we are allowed to write */
	if (!(uds_fd_table[minor].mode & S_IWUSR)) {
		/* socket is shutdown for writing */
		return EPIPE;
	}

	if (size > PIPE_BUF) {
		/* message is too big to ever write to the PIPE */
		return EMSGSIZE;
	}

	if (uds_fd_table[minor].type == SOCK_STREAM ||
			uds_fd_table[minor].type == SOCK_SEQPACKET) {
		/* if we're writing with a connection oriented socket,
		 * then it needs a peer to write to
		 */
		if (uds_fd_table[minor].peer == -1) {
			if (uds_fd_table[minor].err == ECONNRESET) {

				uds_fd_table[minor].err = 0;
				return ECONNRESET;
			} else {
				return ENOTCONN;
			}
		} else {
			peer = uds_fd_table[minor].peer;
		}
	} else /* uds_fd_table[minor].type == SOCK_DGRAM */ {
		peer = -1;

		/* locate the "peer" we want to write to */
		for (i = 0; i < NR_FDS; i++) {

			/* look for a SOCK_DGRAM socket that is bound on
			 * the target address
			 */
			if (uds_fd_table[i].type == SOCK_DGRAM &&
				uds_fd_table[i].addr.sun_family == AF_UNIX &&
				!strncmp(uds_fd_table[minor].target.sun_path,
				uds_fd_table[i].addr.sun_path, UNIX_PATH_MAX)) {

				peer = i;
				break;
			}
		}
	}

	if (peer == -1) {
		if (pretend)
			return SUSPEND;

		return ENOENT;
	}

	/* check if we write to a closed pipe */
	if (!(uds_fd_table[peer].mode & S_IRUSR)) {
		return EPIPE;
	}

	/* we have to preserve the boundary for DGRAM. if there's
	 * already a packet waiting, discard it silently and pretend
	 * it was written.
	 */
	if(uds_fd_table[minor].type == SOCK_DGRAM &&
		uds_fd_table[peer].size > 0) {
		return size;
	}

	/* check if write would overrun buffer. check if message
	 * SEQPACKET wouldn't write to an empty buffer. check if
	 * connectionless sockets have a target to write to.
	 */
	if ((uds_fd_table[peer].pos+uds_fd_table[peer].size+size > PIPE_BUF) ||
		((uds_fd_table[minor].type == SOCK_SEQPACKET) &&
		uds_fd_table[peer].size > 0)) {

		if (pretend) {
			return SUSPEND;
		}

		/* if needed revive the reader */
		if (uds_fd_table[peer].suspended == UDS_SUSPENDED_READ)
			uds_unsuspend(peer);

#if DEBUG == 1
	printf("(uds) [%d] suspending write request\n", minor);
#endif

		/* Process is reading from an empty pipe,
		 * suspend it so some bytes can be written
		 */
		return EDONTREPLY;
	}

	if (pretend) {
		return size;
	}

	/* Prepare Request to the FS side of PFS */
	fs_m_in.m_source = endpt;
	fs_m_in.m_type = REQ_WRITE;
	fs_m_in.REQ_INODE_NR = uds_fd_table[peer].inode_nr;
	fs_m_in.REQ_GRANT = grant;
	fs_m_in.REQ_SEEK_POS_HI = 0;
	fs_m_in.REQ_SEEK_POS_LO = uds_fd_table[peer].pos +
					uds_fd_table[peer].size;
	fs_m_in.REQ_NBYTES = size;

	/* Request the write */
	rc = fs_readwrite(&fs_m_in, &fs_m_out);
	if (rc != OK) {
		printf("PFS: fs_readwrite returned %d\n", rc);
		return rc;
	}

	/* Process the response */
#if DEBUG == 1
	printf("(uds) [%d] write complete\n", minor);
#endif
	/* increase the count of unread bytes */
	uds_fd_table[peer].size += fs_m_out.RES_NBYTES;

	/* fill in the source address to be returned by recvfrom & recvmsg */
	if (uds_fd_table[minor].type == SOCK_DGRAM) {
		memcpy(&uds_fd_table[peer].source, &uds_fd_table[minor].addr,
						sizeof(struct sockaddr_un));
	}

	/* revive peer that was waiting for us to write */
	if (uds_fd_table[peer].suspended == UDS_SUSPENDED_READ)
		uds_unsuspend(peer);

	/* see if peer is blocked on select(); if the peer wants to know about
	 * data ready to read and it doesn't know about it already, then let
	 * the peer know we have data for it.
	 */
	if ((uds_fd_table[peer].sel_ops & CDEV_OP_RD) &&
			fs_m_out.RES_NBYTES > 0) {
		/* a read on peer is possible now */
		chardriver_reply_select(uds_fd_table[peer].sel_endpt, peer,
			CDEV_OP_RD);
		uds_fd_table[peer].sel_ops &= ~CDEV_OP_RD;
	}

	return fs_m_out.RES_NBYTES; /* return number of bytes written */
}

static ssize_t uds_read(devminor_t minor, u64_t position, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int flags, cdev_id_t id)
{
	ssize_t rc;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_read() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return ENXIO;

	if (uds_fd_table[minor].state != UDS_INUSE) {
		/* attempted to read from a socket that hasn't been opened --
		 * something is very wrong :(
		 */
		return EINVAL;
	}

	rc = uds_perform_read(minor, endpt, grant, size, 0);

	/* If the call couldn't complete, suspend the caller. */
	if (rc == EDONTREPLY) {
		uds_fd_table[minor].suspended = UDS_SUSPENDED_READ;
		uds_fd_table[minor].susp_endpt = endpt;
		uds_fd_table[minor].susp_grant = grant;
		uds_fd_table[minor].susp_size = size;
		uds_fd_table[minor].susp_id = id;

		/* If the call wasn't supposed to block, cancel immediately. */
		if (flags & CDEV_NONBLOCK) {
			uds_cancel(minor, endpt, id);

			rc = EAGAIN;
		}
	}

	return rc;
}

static ssize_t uds_write(devminor_t minor, u64_t position, endpoint_t endpt,
	cp_grant_id_t grant, size_t size, int flags, cdev_id_t id)
{
	ssize_t rc;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_write() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return ENXIO;

	if (uds_fd_table[minor].state != UDS_INUSE) {
		/* attempted to write to a socket that hasn't been opened --
		 * something is very wrong :(
		 */
		return EINVAL;
	}

	rc = uds_perform_write(minor, endpt, grant, size, 0);

	/* If the call couldn't complete, suspend the caller. */
	if (rc == EDONTREPLY) {
		uds_fd_table[minor].suspended = UDS_SUSPENDED_WRITE;
		uds_fd_table[minor].susp_endpt = endpt;
		uds_fd_table[minor].susp_grant = grant;
		uds_fd_table[minor].susp_size = size;
		uds_fd_table[minor].susp_id = id;

		/* If the call wasn't supposed to block, cancel immediately. */
		if (flags & CDEV_NONBLOCK) {
			uds_cancel(minor, endpt, id);

			rc = EAGAIN;
		}
	}

	return rc;
}

static int uds_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
	cp_grant_id_t grant, int flags, endpoint_t user_endpt, cdev_id_t id)
{
	int rc;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_ioctl() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return ENXIO;

	if (uds_fd_table[minor].state != UDS_INUSE) {
		/* attempted to perform I/O control on a socket that hasn't
		 * been opened -- something is very wrong :(
		 */
		return EINVAL;
	}

	/* update the owner endpoint */
	uds_fd_table[minor].owner = user_endpt;

	/* let the UDS subsystem handle the actual request */
	rc = uds_do_ioctl(minor, request, endpt, grant);

	/* If the call couldn't complete, suspend the caller. */
	if (rc == EDONTREPLY) {
		/* The suspension type is already set by the IOCTL handler. */
		if (uds_fd_table[minor].suspended == UDS_NOT_SUSPENDED)
			panic("IOCTL did not actually suspend?");
		uds_fd_table[minor].susp_endpt = endpt;
		uds_fd_table[minor].susp_grant = grant;
		uds_fd_table[minor].susp_size = 0; /* irrelevant */
		uds_fd_table[minor].susp_id = id;

		/* If the call wasn't supposed to block, cancel immediately. */
		if (flags & CDEV_NONBLOCK) {
			uds_cancel(minor, endpt, id);

			rc = EAGAIN;
		}
	}

	return rc;
}

void uds_unsuspend(devminor_t minor)
{
	int r;
	uds_fd_t *fdp;

	fdp = &uds_fd_table[minor];

	switch (fdp->suspended) {
	case UDS_SUSPENDED_READ:
		r = uds_perform_read(minor, fdp->susp_endpt, fdp->susp_grant,
			fdp->susp_size, 0);

		if (r == EDONTREPLY)
			return;

		break;

	case UDS_SUSPENDED_WRITE:
		r = uds_perform_write(minor, fdp->susp_endpt, fdp->susp_grant,
			fdp->susp_size, 0);

		if (r == EDONTREPLY)
			return;

		break;

	case UDS_SUSPENDED_CONNECT:
	case UDS_SUSPENDED_ACCEPT:
		/* In both cases, the caller already set up the connection.
		 * The only thing to do here is unblock.
		 */
		r = OK;

		break;

	default:
		panic("unknown suspension type %d", fdp->suspended);
	}

	chardriver_reply_task(fdp->susp_endpt, fdp->susp_id, r);

	fdp->suspended = UDS_NOT_SUSPENDED;
}

static int uds_cancel(devminor_t minor, endpoint_t endpt, cdev_id_t id)
{
	uds_fd_t *fdp;
	int i, j;

#if DEBUG == 1
	static int call_count = 0;
	printf("(uds) [%d] uds_cancel() call_count=%d\n", minor, ++call_count);
#endif

	if (minor < 0 || minor >= NR_FDS) return EDONTREPLY;

	fdp = &uds_fd_table[minor];

	if (fdp->state != UDS_INUSE) {
		printf("PFS: cancel request for closed minor %d\n", minor);
		return EDONTREPLY;
	}

	/* Make sure the cancel request is for a request we're hanging on. */
	if (fdp->suspended == UDS_NOT_SUSPENDED || fdp->susp_endpt != endpt ||
			fdp->susp_id != id) {
		return EDONTREPLY;	/* this happens. */
	}

	/* The system call was cancelled, so the socket is not suspended
	 * anymore.
	 */
	switch (fdp->suspended) {
	case UDS_SUSPENDED_ACCEPT:	/* accept() */
		/* partial accept() only changes
		 * uds_fd_table[minorparent].child
		 */
		for (i = 0; i < NR_FDS; i++) {
			if (uds_fd_table[i].child == minor) {
				uds_fd_table[i].child = -1;
			}
		}

		break;

	case UDS_SUSPENDED_CONNECT:	/* connect() */
		/* partial connect() sets addr and adds minor to server backlog
		 */

		for (i = 0; i < NR_FDS; i++) {
			/* find a socket that is in use. */
			if (uds_fd_table[i].state != UDS_INUSE)
				continue;

			/* see if minor is in the backlog */
			for (j = 0; j < uds_fd_table[i].backlog_size; j++) {
				if (uds_fd_table[i].backlog[j] == minor) {

					/* remove from backlog */
					uds_fd_table[i].backlog[j] = -1;
				}
			}
		}

		/* clear the address */
		memset(&(uds_fd_table[minor].addr), '\0',
			sizeof(struct sockaddr_un));

		break;

	case UDS_SUSPENDED_READ:
	case UDS_SUSPENDED_WRITE:
		/* Nothing more to do. */
		break;

	default:
		panic("unknown suspension type %d", fdp->suspended);
	}

	fdp->suspended = UDS_NOT_SUSPENDED;

	return EINTR;	/* reply to the original request */
}