/**
* Create a writable mimic directory based on reference directory.
*
* The mimic directory is a tmpfs populated with bind mounts to the (possibly
* read only) directories in the reference directory. While all the read-only
* content stays read-only the actual mimic directory is writable so additional
* content can be placed there.
*
* Flags are forwarded to sc_quirk_mkdir_bind()
**/
static void sc_quirk_create_writable_mimic(const char *mimic_dir,
const char *ref_dir, unsigned flags)
{
debug("creating writable mimic directory %s based on %s", mimic_dir,
ref_dir);
sc_quirk_setup_tmpfs(mimic_dir);
// Now copy the ownership and permissions of the mimicked directory
struct stat stat_buf;
if (stat(ref_dir, &stat_buf) < 0) {
die("cannot stat %s", ref_dir);
}
if (chown(mimic_dir, stat_buf.st_uid, stat_buf.st_gid) < 0) {
die("cannot chown for %s", mimic_dir);
}
if (chmod(mimic_dir, stat_buf.st_mode) < 0) {
die("cannot chmod for %s", mimic_dir);
}
debug("bind-mounting all the files from the reference directory");
DIR *dirp SC_CLEANUP(sc_cleanup_closedir) = NULL;
dirp = opendir(ref_dir);
if (dirp == NULL) {
die("cannot open reference directory %s", ref_dir);
}
struct dirent *entryp = NULL;
do {
char src_name[PATH_MAX * 2] = { 0 };
char dest_name[PATH_MAX * 2] = { 0 };
// Set errno to zero, if readdir fails it will not only return null but
// set errno to a non-zero value. This is how we can differentiate
// end-of-directory from an actual error.
errno = 0;
entryp = readdir(dirp);
if (entryp == NULL && errno != 0) {
die("cannot read another directory entry");
}
if (entryp == NULL) {
break;
}
if (strcmp(entryp->d_name, ".") == 0
|| strcmp(entryp->d_name, "..") == 0) {
continue;
}
if (entryp->d_type != DT_DIR && entryp->d_type != DT_REG) {
die("unsupported entry type of file %s (%d)",
entryp->d_name, entryp->d_type);
}
sc_must_snprintf(src_name, sizeof src_name, "%s/%s", ref_dir,
entryp->d_name);
sc_must_snprintf(dest_name, sizeof dest_name, "%s/%s",
mimic_dir, entryp->d_name);
sc_quirk_mkdir_bind(src_name, dest_name, flags);
} while (entryp != NULL);
}
/**
* Setup a quirk for LXD.
*
* An existing LXD snap relies on pre-chroot behavior to access /var/lib/lxd
* while in devmode. Since that directory doesn't exist in the core snap the
* quirk punches a custom hole so that this directory shows the hostfs content
* if such directory exists on the host.
*
* See: https://bugs.launchpad.net/snap-confine/+bug/1613845
**/
static void sc_setup_lxd_quirk(void)
{
const char *hostfs_lxd_dir = SC_HOSTFS_DIR "/var/lib/lxd";
if (access(hostfs_lxd_dir, F_OK) == 0) {
const char *lxd_dir = "/var/lib/lxd";
debug("setting up quirk for LXD (see LP: #1613845)");
sc_quirk_mkdir_bind(hostfs_lxd_dir, lxd_dir,
MS_REC | MS_SLAVE | MS_NODEV | MS_NOSUID |
MS_NOEXEC);
}
}
/**
* Create a writable mimic directory based on reference directory.
*
* The mimic directory is a tmpfs populated with bind mounts to the (possibly
* read only) directories in the reference directory. While all the read-only
* content stays read-only the actual mimic directory is writable so additional
* content can be placed there.
*
* Flags are forwarded to sc_quirk_mkdir_bind()
**/
static void sc_quirk_create_writable_mimic(const char *mimic_dir,
const char *ref_dir, unsigned flags)
{
debug("creating writable mimic directory %s based on %s", mimic_dir,
ref_dir);
sc_quirk_setup_tmpfs(mimic_dir);
debug("bind-mounting all the files from the reference directory");
DIR *dirp __attribute__ ((cleanup(sc_cleanup_closedir))) = NULL;
dirp = opendir(ref_dir);
if (dirp == NULL) {
die("cannot open reference directory %s", ref_dir);
}
struct dirent *entryp = NULL;
do {
char src_name[PATH_MAX * 2];
char dest_name[PATH_MAX * 2];
// Set errno to zero, if readdir fails it will not only return null but
// set errno to a non-zero value. This is how we can differentiate
// end-of-directory from an actual error.
errno = 0;
entryp = readdir(dirp);
if (entryp == NULL && errno != 0) {
die("cannot read another directory entry");
}
if (entryp == NULL) {
break;
}
if (strcmp(entryp->d_name, ".") == 0
|| strcmp(entryp->d_name, "..") == 0) {
continue;
}
if (entryp->d_type != DT_DIR && entryp->d_type != DT_REG) {
die("unsupported entry type of file %s (%d)",
entryp->d_name, entryp->d_type);
}
must_snprintf(src_name, sizeof src_name, "%s/%s", ref_dir,
entryp->d_name);
must_snprintf(dest_name, sizeof dest_name, "%s/%s", mimic_dir,
entryp->d_name);
sc_quirk_mkdir_bind(src_name, dest_name, flags);
} while (entryp != NULL);
}
