On Thu, Nov 07, 2013 at 10:50:59PM +0000, submit@xxxxxxxxx wrote:
> mac-cxs-XK:pochd XK$ gcc -o test test.c
> mac-cxs-XK:pochd XK$ ls
> test test.c
> mac-cxs-XK:pochd XK$ mkdir DIR1
> mac-cxs-XK:pochd XK$ ./test DIR1 Hardlink1
> link(3) return= -1
> mac-cxs-XK:pochd XK$ mkdir DIR1/DIR2
> mac-cxs-XK:pochd XK$ ./test DIR1/DIR2 Hardlink2
> link(3) return= 0
> mac-cxs-XK:pochd XK$ cd DIR1
> mac-cxs-XK:DIR1 XK$ mkdir DIR2/DIR3
> mac-cxs-XK:DIR1 XK$ ../test DIR2/DIR3 Hardlink3
> link(3) return= 0
> mac-cxs-XK:DIR1 XK$ cd DIR2
> mac-cxs-XK:DIR2 XK$ mkdir DIR3/DIR4
> mac-cxs-XK:DIR2 XK$ ../../test DIR3/DIR4 Hardlink4
> link(3) return= -1
The first failing case is easily explained: directory hard links cannot have the same
parent. This is checked in hfs_link.c[1] in hfs_vnop_link(). Search for the following
comment:
/*
* All directory links must reside in an non-ARCHIVED hierarchy.
*/
if (v_type == VDIR) {
/*
* - Source parent and destination parent cannot match
* - A link is not permitted in the root directory
* - Parent of 'pointed at' directory is not the root directory
* - The 'pointed at' directory (source) is not an ancestor
* of the new directory hard link (destination).
* - No ancestor of the new directory hard link (destination)
* is a directory hard link.
*/
if ((parentcnid == tdcp->c_fileid) ||
(tdcp->c_fileid == kHFSRootFolderID) ||
(parentcnid == kHFSRootFolderID) ||
cat_check_link_ancestry(hfsmp, tdcp->c_fileid, cp->c_fileid)) {
error = EPERM; /* abide by the rules, you did not */
goto out;
}
}
Does this also explain the last case?
S.
[1] http://opensource.apple.com/source/xnu/xnu-2422.1.72/bsd/hfs/hfs_link.c
