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nspawn: tweaks to /etc/resolv.conf management

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Handle properly if /etc is a symlink (i.e. make sure we don't follow the
symlink outside the image). Also follow /etc/resolv.conf if it is a
symlink, and use the resolved path when creating a mount point and
mounting (as both of these operations follow symlinks and rally
shouldn't).

Handle more types of read-only errors as debug-level issues.
This commit is contained in:
Lennart Poettering 2016-12-21 00:44:00 +01:00
parent 8ccf7e9e96
commit 87447ae459
1 changed files with 22 additions and 10 deletions
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32
src/nspawn/nspawn.c
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@ -1311,31 +1311,43 @@ static int setup_timezone(const char *dest) {
}
static int setup_resolv_conf(const char *dest) {
const char *where = NULL;
int r;
_cleanup_free_ char *resolved = NULL, *etc = NULL;
const char *where;
int r, found;
assert(dest);
if (arg_private_network)
return 0;
/* Fix resolv.conf, if possible */
where = prefix_roota(dest, "/etc/resolv.conf");
r = chase_symlinks("/etc", dest, CHASE_PREFIX_ROOT, &etc);
if (r < 0) {
log_warning_errno(r, "Failed to resolve /etc path in container, ignoring: %m");
return 0;
}
where = strjoina(etc, "/resolv.conf");
found = chase_symlinks(where, dest, CHASE_NONEXISTENT, &resolved);
if (found < 0) {
log_warning_errno(found, "Failed to resolve /etc/resolv.conf path in container, ignoring: %m");
return 0;
}
if (access("/run/systemd/resolve/resolv.conf", F_OK) >= 0 &&
access("/usr/lib/systemd/resolv.conf", F_OK) >= 0) {
access("/usr/lib/systemd/resolv.conf", F_OK) >= 0) {
/* resolved is enabled on the host. In this, case bind mount its static resolv.conf file into the
* container, so that the container can use the host's resolver. Given that network namespacing is
* disabled it's only natural of the container also uses the host's resolver. It also has the big
* advantage that the container will be able to follow the host's DNS server configuration changes
* transparently. */
(void) touch(where);
if (found == 0) /* missing? */
(void) touch(resolved);
r = mount_verbose(LOG_WARNING, "/usr/lib/systemd/resolv.conf", where, NULL, MS_BIND, NULL);
r = mount_verbose(LOG_DEBUG, "/usr/lib/systemd/resolv.conf", resolved, NULL, MS_BIND, NULL);
if (r >= 0)
return mount_verbose(LOG_ERR, NULL, where, NULL,
MS_BIND|MS_REMOUNT|MS_RDONLY|MS_NOSUID|MS_NODEV, NULL);
return mount_verbose(LOG_ERR, NULL, resolved, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_NOSUID|MS_NODEV, NULL);
}
/* If that didn't work, let's copy the file */
@ -1346,7 +1358,7 @@ static int setup_resolv_conf(const char *dest) {
*
* If the disk image is read-only, there's also no point in complaining.
*/
log_full_errno(IN_SET(r, -ELOOP, -EROFS) ? LOG_DEBUG : LOG_WARNING, r,
log_full_errno(IN_SET(r, -ELOOP, -EROFS, -EACCES, -EPERM) ? LOG_DEBUG : LOG_WARNING, r,
"Failed to copy /etc/resolv.conf to %s, ignoring: %m", where);
return 0;
}