+ if (how & LOCK_EX)
+ lf.l_type = F_WRLCK;
+ else if (how & LOCK_SH)
+ lf.l_type = F_RDLCK;
+ else
+ return (EBADF);
+ fp->f_flag |= FHASLOCK;
+ if (how & LOCK_NB)
+ return (VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK));
+ return (VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK|F_WAIT));
+}
+
+/*
+ * File Descriptor pseudo-device driver (/dev/fd/).
+ *
+ * Opening minor device N dup()s the file (if any) connected to file
+ * descriptor N belonging to the calling process. Note that this driver
+ * consists of only the ``open()'' routine, because all subsequent
+ * references to this file will be direct to the other driver.
+ */
+/* ARGSUSED */
+int
+fdopen(dev, mode, type, p)
+ dev_t dev;
+ int mode, type;
+ struct proc *p;
+{
+
+ /*
+ * XXX Kludge: set curproc->p_dupfd to contain the value of the
+ * the file descriptor being sought for duplication. The error
+ * return ensures that the vnode for this device will be released
+ * by vn_open. Open will detect this special error and take the
+ * actions in dupfdopen below. Other callers of vn_open or VOP_OPEN
+ * will simply report the error.
+ */
+ p->p_dupfd = minor(dev);
+ return (ENODEV);
+}
+
+/*
+ * Duplicate the specified descriptor to a free descriptor.
+ */
+int
+dupfdopen(fdp, indx, dfd, mode, error)
+ register struct filedesc *fdp;
+ register int indx, dfd;
+ int mode;
+ int error;
+{
+ register struct file *wfp;
+ struct file *fp;
+
+ /*
+ * If the to-be-dup'd fd number is greater than the allowed number
+ * of file descriptors, or the fd to be dup'd has already been
+ * closed, reject. Note, check for new == old is necessary as
+ * falloc could allocate an already closed to-be-dup'd descriptor
+ * as the new descriptor.
+ */
+ fp = fdp->fd_ofiles[indx];
+ if ((u_int)dfd >= fdp->fd_nfiles ||
+ (wfp = fdp->fd_ofiles[dfd]) == NULL || fp == wfp)
+ return (EBADF);
+
+ /*
+ * There are two cases of interest here.
+ *
+ * For ENODEV simply dup (dfd) to file descriptor
+ * (indx) and return.
+ *
+ * For ENXIO steal away the file structure from (dfd) and
+ * store it in (indx). (dfd) is effectively closed by
+ * this operation.
+ *
+ * Any other error code is just returned.
+ */
+ switch (error) {
+ case ENODEV:
+ /*
+ * Check that the mode the file is being opened for is a
+ * subset of the mode of the existing descriptor.
+ */
+ if (((mode & (FREAD|FWRITE)) | wfp->f_flag) != wfp->f_flag)
+ return (EACCES);
+ fdp->fd_ofiles[indx] = wfp;
+ fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
+ wfp->f_count++;
+ if (indx > fdp->fd_lastfile)
+ fdp->fd_lastfile = indx;
+ return (0);
+
+ case ENXIO:
+ /*
+ * Steal away the file pointer from dfd, and stuff it into indx.
+ */
+ fdp->fd_ofiles[indx] = fdp->fd_ofiles[dfd];
+ fdp->fd_ofiles[dfd] = NULL;
+ fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
+ fdp->fd_ofileflags[dfd] = 0;
+ /*
+ * Complete the clean up of the filedesc structure by
+ * recomputing the various hints.
+ */
+ if (indx > fdp->fd_lastfile)
+ fdp->fd_lastfile = indx;
+ else
+ while (fdp->fd_lastfile > 0 &&
+ fdp->fd_ofiles[fdp->fd_lastfile] == NULL)
+ fdp->fd_lastfile--;
+ if (dfd < fdp->fd_freefile)
+ fdp->fd_freefile = dfd;
+ return (0);
+
+ default:
+ return (error);