Add hard link support to gensquashfs and tar2sqfs

In libtar, set a special flag if the header is actually a hard link.

In tar2sqfs, create a hard link node and skip the rest for hard links.
Also refues to set the root attributes from a hard link, it may refere
to a node that we have missed earlier, there is nothing else that we
can do here.

In fstree_from_file, add a "link" command for adding hard links.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

6 files changed, 34 insertions, 5 deletions

diff --git a/doc/gensquashfs.1 b/doc/gensquashfs.1
index 04dd968..0de39bf 100644
--- a/doc/gensquashfs.1
+++ b/doc/gensquashfs.1
@@ -105,6 +105,7 @@ file <path> <mode> <uid> <gid> [<location>]
 dir <path> <mode> <uid> <gid>
 nod <path> <mode> <uid> <gid> <dev_type> <maj> <min>
 slink <path> <mode> <uid> <gid> <target>
+link <path> <dummy> <dummy> <dummy> <target>
 pipe <path> <mode> <uid> <gid>
 sock <path> <mode> <uid> <gid>
 .fi
@@ -131,7 +132,7 @@ Optional location of the input file. Can be specified relative to either the
 description file or the pack directory. If omitted, the image path is used
 as a relative path.
 T}
-<target>;Symlink target.
+<target>;Symlink or hardlink target.
 <mode>;Mode/permissions of the entry.
 <uid>;Numeric user id.
 <gid>;Numeric group id.
diff --git a/include/tar.h b/include/tar.h
index 22563c4..617148f 100644
--- a/include/tar.h
+++ b/include/tar.h
@@ -84,6 +84,7 @@ typedef struct {
 	sqfs_u64 actual_size;
 	sqfs_u64 record_size;
 	bool unknown_record;
+	bool is_hard_link;
 	tar_xattr_t *xattr;
 
 	/* broken out since struct stat could contain
diff --git a/lib/fstree/fstree_from_file.c b/lib/fstree/fstree_from_file.c
index 9cdf9a1..bf11755 100644
--- a/lib/fstree/fstree_from_file.c
+++ b/lib/fstree/fstree_from_file.c
@@ -62,6 +62,19 @@ static int add_file(fstree_t *fs, const char *filename, size_t line_num,
 	return add_generic(fs, filename, line_num, path, basic, extra);
 }
 
+static int add_hard_link(fstree_t *fs, const char *filename, size_t line_num,
+			 const char *path, struct stat *basic, const char *extra)
+{
+	(void)basic;
+
+	if (fstree_add_hard_link(fs, path, extra) == NULL) {
+		fprintf(stderr, "%s: " PRI_SZ ": %s\n",
+			filename, line_num, strerror(errno));
+		return -1;
+	}
+	return 0;
+}
+
 static const struct {
 	const char *keyword;
 	unsigned int mode;
@@ -71,6 +84,7 @@ static const struct {
 } file_list_hooks[] = {
 	{ "dir", S_IFDIR, false, add_generic },
 	{ "slink", S_IFLNK, true, add_generic },
+	{ "link", 0, true, add_hard_link },
 	{ "nod", 0, true, add_device },
 	{ "pipe", S_IFIFO, false, add_generic },
 	{ "sock", S_IFSOCK, false, add_generic },
diff --git a/lib/tar/read_header.c b/lib/tar/read_header.c
index 7d209ae..f82f9a5 100644
--- a/lib/tar/read_header.c
+++ b/lib/tar/read_header.c
@@ -345,8 +345,7 @@ static int decode_header(const tar_header_t *hdr, unsigned int set_by_pax,
 		out->sb.st_mode |= S_IFREG;
 		break;
 	case TAR_TYPE_LINK:
-		/* XXX: hard links are not support yet */
-		out->sb.st_mode = S_IFLNK | 0777;
+		out->is_hard_link = true;
 		break;
 	case TAR_TYPE_SLINK:
 		out->sb.st_mode = S_IFLNK | 0777;
diff --git a/mkfs/options.c b/mkfs/options.c
index 39ecdc7..fd6ca46 100644
--- a/mkfs/options.c
+++ b/mkfs/options.c
@@ -112,6 +112,7 @@ const char *help_details =
 "dir <path> <mode> <uid> <gid>\n"
 "nod <path> <mode> <uid> <gid> <dev_type> <maj> <min>\n"
 "slink <path> <mode> <uid> <gid> <target>\n"
+"link <path> <dummy> <dummy> <dummy> <target>\n"
 "pipe <path> <mode> <uid> <gid>\n"
 "sock <path> <mode> <uid> <gid>\n"
 "\n"
@@ -120,7 +121,7 @@ const char *help_details =
 "<location>   If given, location of the input file. Either absolute or relative\n"
 "             to the description file. If omitted, the image path is used,\n"
 "             relative to the description file.\n"
-"<target>     Symlink target.\n"
+"<target>     Symlink or hardlink target.\n"
 "<mode>       Mode/permissions of the entry.\n"
 "<uid>        Numeric user id.\n"
 "<gid>        Numeric group id.\n"
diff --git a/tar/tar2sqfs.c b/tar/tar2sqfs.c
index 63933eb..f522239 100644
--- a/tar/tar2sqfs.c
+++ b/tar/tar2sqfs.c
@@ -355,6 +355,19 @@ static int create_node_and_repack_data(tar_header_decoded_t *hdr)
 {
 	tree_node_t *node;
 
+	if (hdr->is_hard_link) {
+		node = fstree_add_hard_link(&sqfs.fs, hdr->name,
+					    hdr->link_target);
+		if (node == NULL)
+			goto fail_errno;
+
+		if (!cfg.quiet) {
+			printf("Hard link %s -> %s\n", hdr->name,
+			       hdr->link_target);
+		}
+		return 0;
+	}
+
 	if (!keep_time) {
 		hdr->sb.st_mtime = sqfs.fs.defaults.st_mtime;
 	}
@@ -385,7 +398,7 @@ fail_errno:
 
 static int set_root_attribs(const tar_header_decoded_t *hdr)
 {
-	if (!S_ISDIR(hdr->sb.st_mode)) {
+	if (hdr->is_hard_link || !S_ISDIR(hdr->sb.st_mode)) {
 		fprintf(stderr, "'%s' is not a directory!\n", hdr->name);
 		return -1;
 	}