r8746: replace opendir/readdir/telldir/seekdir/closedir on systems where they

are broken (apparently all BSD systems). This breakage leads to unlink
on files in an open directory causing a later seekdir to miss
files. The bug happens due to a block boundary bug in the BSD libc
implementation of these calls.

This replacement code also fixes a severe memory usage problem with
telldir that can cause closedir() to take an arbitrary amount of time.

I have reported the bug in readdir to Greg Lehey (a FreeBSD maintainer)
(This used to be commit e1bf7c4279fbc03a52497d24cea375e75059cba1)

1 files changed, 138 insertions, 0 deletions

diff --git a/source4/lib/replace/repdir/repdir.c b/source4/lib/replace/repdir/repdir.c
new file mode 100644
index 0000000000..9c81355c68
--- /dev/null
+++ b/source4/lib/replace/repdir/repdir.c
@@ -0,0 +1,138 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   Copyright (C) Andrew Tridgell 2005
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+/*
+  a replacement for opendir/readdir/telldir/seekdir/closedir for BSD systems
+
+  This is needed because the existing directory handling in FreeBSD
+  and OpenBSD (and possibly NetBSD) doesn't correctly handle unlink()
+  on files in a directory where telldir() has been used. On a block
+  boundary it will occasionally miss a file when seekdir() is used to
+  return to a position previously recorded with telldir().
+
+  This also fixes a severe performance and memory usage problem with
+  telldir() on BSD systems. Each call to telldir() in BSD adds an
+  entry to a linked list, and those entries are cleaned up on
+  closedir(). This means with a large directory closedir() can take an
+  arbitrary amount of time, causing network timeouts as millions of
+  telldir() entries are freed
+
+  Note! This replacement code is not portable. It relies on getdents()
+  always leaving the file descriptor at a seek offset that is a
+  multiple of DIR_BUF_SIZE. If the code detects that this doesn't
+  happen then it will abort(). It also does not handle directories
+  with offsets larger than can be stored in a long,
+
+  This code is available under other free software licenses as
+  well. Contact the author.
+*/
+
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <dirent.h>
+
+#define DIR_BUF_BITS 9
+#define DIR_BUF_SIZE (1<<DIR_BUF_BITS)
+
+struct dir_buf {
+	int fd;
+	int nbytes, ofs;
+	off_t seekpos;
+	char buf[DIR_BUF_SIZE];
+};
+
+DIR *opendir(const char *dname)
+{
+	struct dir_buf *d;
+	d = malloc(sizeof(*d));
+	if (d == NULL) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	d->fd = open(dname, O_RDONLY);
+	if (d->fd == -1) {
+		free(d);
+		return NULL;
+	}
+	d->ofs = 0;
+	d->seekpos = 0;
+	d->nbytes = 0;
+	return (DIR *)d;
+}
+
+struct dirent *readdir(DIR *dir)
+{
+	struct dir_buf *d = (struct dir_buf *)dir;
+	struct dirent *de;
+
+	if (d->ofs >= d->nbytes) {
+		d->seekpos = lseek(d->fd, 0, SEEK_CUR);
+		d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
+		d->ofs = 0;
+	}
+	if (d->ofs >= d->nbytes) {
+		return NULL;
+	}
+	de = (struct dirent *)&d->buf[d->ofs];
+	d->ofs += de->d_reclen;
+	return de;
+}
+
+long telldir(DIR *dir)
+{
+	struct dir_buf *d = (struct dir_buf *)dir;
+	if (d->ofs >= d->nbytes) {
+		d->seekpos = lseek(d->fd, 0, SEEK_CUR);
+		d->ofs = 0;
+		d->nbytes = 0;
+	}
+	/* this relies on seekpos always being a multiple of
+	   DIR_BUF_SIZE. Is that always true on BSD systems? */
+	if (d->seekpos & (DIR_BUF_SIZE-1)) {
+		abort();
+	}
+	return d->seekpos + d->ofs;
+}
+
+void seekdir(DIR *dir, long ofs)
+{
+	struct dir_buf *d = (struct dir_buf *)dir;
+	d->seekpos = lseek(d->fd, ofs & ~(DIR_BUF_SIZE-1), SEEK_SET);
+	d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
+	d->ofs = 0;
+	while (d->ofs < (ofs & (DIR_BUF_SIZE-1))) {
+		if (readdir(dir) == NULL) break;
+	}
+}
+
+int closedir(DIR *dir)
+{
+	struct dir_buf *d = (struct dir_buf *)dir;
+	int r = close(d->fd);
+	if (r != 0) {
+		return r;
+	}
+	free(d);
+	return 0;
+}
+