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nspawn: add greater control over how /etc/resolv.conf is handled

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Fixes: #8014 #1781
This commit is contained in:
Lennart Poettering
2018-05-22 16:19:26 +02:00
parent 8904ab86b0
commit 09d423e921
6 changed files with 155 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/nspawn/nspawn-gperf.gperf
+1
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@@ -53,6 +53,7 @@ Exec.Hostname, config_parse_hostname, 0, of
Exec.NoNewPrivileges, config_parse_tristate, 0, offsetof(Settings, no_new_privileges)
Exec.OOMScoreAdjust, config_parse_oom_score_adjust, 0, 0
Exec.CPUAffinity, config_parse_cpu_affinity, 0, 0
Exec.ResolvConf, config_parse_resolv_conf, 0, offsetof(Settings, resolv_conf)
Files.ReadOnly, config_parse_tristate, 0, offsetof(Settings, read_only)
Files.Volatile, config_parse_volatile_mode, 0, offsetof(Settings, volatile_mode)
Files.Bind, config_parse_bind, 0, 0
src/nspawn/nspawn-settings.c
+16
View File
@@ -16,6 +16,7 @@
#include "process-util.h"
#include "rlimit-util.h"
#include "socket-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
@@ -35,6 +36,7 @@ int settings_load(FILE *f, const char *path, Settings **ret) {
s->start_mode = _START_MODE_INVALID;
s->personality = PERSONALITY_INVALID;
s->userns_mode = _USER_NAMESPACE_MODE_INVALID;
s->resolv_conf = _RESOLV_CONF_MODE_INVALID;
s->uid_shift = UID_INVALID;
s->uid_range = UID_INVALID;
s->no_new_privileges = -1;
@@ -724,3 +726,17 @@ int config_parse_cpu_affinity(
return 0;
}
DEFINE_CONFIG_PARSE_ENUM(config_parse_resolv_conf, resolv_conf_mode, ResolvConfMode, "Failed to parse resolv.conf mode");
static const char *const resolv_conf_mode_table[_RESOLV_CONF_MODE_MAX] = {
[RESOLV_CONF_OFF] = "off",
[RESOLV_CONF_COPY_HOST] = "copy-host",
[RESOLV_CONF_COPY_STATIC] = "copy-static",
[RESOLV_CONF_BIND_HOST] = "bind-host",
[RESOLV_CONF_BIND_STATIC] = "bind-static",
[RESOLV_CONF_DELETE] = "delete",
[RESOLV_CONF_AUTO] = "auto",
};
DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(resolv_conf_mode, ResolvConfMode, RESOLV_CONF_AUTO);
src/nspawn/nspawn-settings.h
+21 -3
View File
@@ -33,6 +33,18 @@ typedef enum UserNamespaceMode {
_USER_NAMESPACE_MODE_INVALID = -1,
} UserNamespaceMode;
typedef enum ResolvConfMode {
RESOLV_CONF_OFF,
RESOLV_CONF_COPY_HOST,
RESOLV_CONF_COPY_STATIC,
RESOLV_CONF_BIND_HOST,
RESOLV_CONF_BIND_STATIC,
RESOLV_CONF_DELETE,
RESOLV_CONF_AUTO,
_RESOLV_CONF_MODE_MAX,
_RESOLV_CONF_MODE_INVALID = -1
} ResolvConfMode;
typedef enum SettingsMask {
SETTING_START_MODE = UINT64_C(1) << 0,
SETTING_ENVIRONMENT = UINT64_C(1) << 1,
@@ -55,9 +67,10 @@ typedef enum SettingsMask {
SETTING_NO_NEW_PRIVILEGES = UINT64_C(1) << 18,
SETTING_OOM_SCORE_ADJUST = UINT64_C(1) << 19,
SETTING_CPU_AFFINITY = UINT64_C(1) << 20,
SETTING_RLIMIT_FIRST = UINT64_C(1) << 21, /* we define one bit per resource limit here */
SETTING_RLIMIT_LAST = UINT64_C(1) << (21 + _RLIMIT_MAX - 1),
_SETTINGS_MASK_ALL = (UINT64_C(1) << (21 + _RLIMIT_MAX)) - 1,
SETTING_RESOLV_CONF = UINT64_C(1) << 21,
SETTING_RLIMIT_FIRST = UINT64_C(1) << 22, /* we define one bit per resource limit here */
SETTING_RLIMIT_LAST = UINT64_C(1) << (22 + _RLIMIT_MAX - 1),
_SETTINGS_MASK_ALL = (UINT64_C(1) << (22 + _RLIMIT_MAX)) - 1,
_FORCE_ENUM_WIDTH = UINT64_MAX
} SettingsMask;
@@ -96,6 +109,7 @@ typedef struct Settings {
bool oom_score_adjust_set;
cpu_set_t *cpuset;
unsigned cpuset_ncpus;
ResolvConfMode resolv_conf;
/* [Image] */
int read_only;
@@ -143,3 +157,7 @@ CONFIG_PARSER_PROTOTYPE(config_parse_syscall_filter);
CONFIG_PARSER_PROTOTYPE(config_parse_hostname);
CONFIG_PARSER_PROTOTYPE(config_parse_oom_score_adjust);
CONFIG_PARSER_PROTOTYPE(config_parse_cpu_affinity);
CONFIG_PARSER_PROTOTYPE(config_parse_resolv_conf);
const char *resolv_conf_mode_to_string(ResolvConfMode a) _const_;
ResolvConfMode resolv_conf_mode_from_string(const char *s) _pure_;
src/nspawn/nspawn.c
+79 -17
View File
@@ -211,6 +211,7 @@ static int arg_oom_score_adjust = 0;
static bool arg_oom_score_adjust_set = false;
static cpu_set_t *arg_cpuset = NULL;
static unsigned arg_cpuset_ncpus = 0;
static ResolvConfMode arg_resolv_conf = RESOLV_CONF_AUTO;
static void help(void) {
@@ -287,6 +288,7 @@ static void help(void) {
" --link-journal=MODE Link up guest journal, one of no, auto, guest, \n"
" host, try-guest, try-host\n"
" -j Equivalent to --link-journal=try-guest\n"
" --resolv-conf=MODE Select mode of /etc/resolv.conf initialization\n"
" --read-only Mount the root directory read-only\n"
" --bind=PATH[:PATH[:OPTIONS]]\n"
" Bind mount a file or directory from the host into\n"
@@ -463,6 +465,7 @@ static int parse_argv(int argc, char *argv[]) {
ARG_NO_NEW_PRIVILEGES,
ARG_OOM_SCORE_ADJUST,
ARG_CPU_AFFINITY,
ARG_RESOLV_CONF,
};
static const struct option options[] = {
@@ -521,6 +524,7 @@ static int parse_argv(int argc, char *argv[]) {
{ "rlimit", required_argument, NULL, ARG_RLIMIT },
{ "oom-score-adjust", required_argument, NULL, ARG_OOM_SCORE_ADJUST },
{ "cpu-affinity", required_argument, NULL, ARG_CPU_AFFINITY },
{ "resolv-conf", required_argument, NULL, ARG_RESOLV_CONF },
{}
};
@@ -1222,6 +1226,21 @@ static int parse_argv(int argc, char *argv[]) {
break;
}
case ARG_RESOLV_CONF:
if (streq(optarg, "help")) {
DUMP_STRING_TABLE(resolv_conf_mode, ResolvConfMode, _RESOLV_CONF_MODE_MAX);
return 0;
}
arg_resolv_conf = resolv_conf_mode_from_string(optarg);
if (arg_resolv_conf < 0) {
log_error("Failed to parse /etc/resolv.conf mode: %s", optarg);
return -EINVAL;
}
arg_settings_mask |= SETTING_RESOLV_CONF;
break;
case '?':
return -EINVAL;
@@ -1507,6 +1526,19 @@ static int setup_timezone(const char *dest) {
return 0;
}
static int have_resolv_conf(const char *path) {
assert(path);
if (access(path, F_OK) < 0) {
if (errno == ENOENT)
return 0;
return log_debug_errno(errno, "Failed to determine whether '%s' is available: %m", path);
}
return 1;
}
static int resolved_listening(void) {
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
_cleanup_free_ char *dns_stub_listener_mode = NULL;
@@ -1536,13 +1568,31 @@ static int resolved_listening(void) {
}
static int setup_resolv_conf(const char *dest) {
_cleanup_free_ char *resolved = NULL, *etc = NULL;
const char *where;
int r, found;
_cleanup_free_ char *etc = NULL;
const char *where, *what;
ResolvConfMode m;
int r;
assert(dest);
if (arg_private_network)
if (arg_resolv_conf == RESOLV_CONF_AUTO) {
if (arg_private_network)
m = RESOLV_CONF_OFF;
else if (have_resolv_conf(STATIC_RESOLV_CONF) > 0 && resolved_listening() > 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. */
m = RESOLV_CONF_BIND_STATIC;
else if (have_resolv_conf("/etc/resolv.conf") > 0)
m = arg_read_only && arg_volatile_mode != VOLATILE_YES ? RESOLV_CONF_BIND_HOST : RESOLV_CONF_COPY_HOST;
else
m = arg_read_only && arg_volatile_mode != VOLATILE_YES ? RESOLV_CONF_OFF : RESOLV_CONF_DELETE;
} else
m = arg_resolv_conf;
if (m == RESOLV_CONF_OFF)
return 0;
r = chase_symlinks("/etc", dest, CHASE_PREFIX_ROOT, &etc);
@@ -1552,38 +1602,46 @@ static int setup_resolv_conf(const char *dest) {
}
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");
if (m == RESOLV_CONF_DELETE) {
if (unlink(where) < 0)
log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno, "Failed to remove '%s', ignoring: %m", where);
return 0;
}
if (access(STATIC_RESOLV_CONF, F_OK) >= 0 &&
resolved_listening() > 0) {
if (IN_SET(m, RESOLV_CONF_BIND_STATIC, RESOLV_CONF_COPY_STATIC))
what = STATIC_RESOLV_CONF;
else
what = "/etc/resolv.conf";
/* 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. */
if (IN_SET(m, RESOLV_CONF_BIND_HOST, RESOLV_CONF_BIND_STATIC)) {
_cleanup_free_ char *resolved = NULL;
int found;
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 (found == 0) /* missing? */
(void) touch(resolved);
r = mount_verbose(LOG_DEBUG, STATIC_RESOLV_CONF, resolved, NULL, MS_BIND, NULL);
r = mount_verbose(LOG_WARNING, what, resolved, NULL, MS_BIND, NULL);
if (r >= 0)
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 */
r = copy_file("/etc/resolv.conf", where, O_TRUNC|O_NOFOLLOW, 0644, 0, COPY_REFLINK);
r = copy_file(what, where, O_TRUNC|O_NOFOLLOW, 0644, 0, COPY_REFLINK);
if (r < 0) {
/* If the file already exists as symlink, let's suppress the warning, under the assumption that
* resolved or something similar runs inside and the symlink points there.
*
* If the disk image is read-only, there's also no point in complaining.
*/
log_full_errno(IN_SET(r, -ELOOP, -EROFS, -EACCES, -EPERM) ? LOG_DEBUG : LOG_WARNING, r,
log_full_errno(!IN_SET(RESOLV_CONF_COPY_HOST, RESOLV_CONF_COPY_STATIC) && 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;
}
@@ -3385,6 +3443,10 @@ static int merge_settings(Settings *settings, const char *path) {
}
}
if ((arg_settings_mask & SETTING_RESOLV_CONF) == 0 &&
settings->resolv_conf != _RESOLV_CONF_MODE_INVALID)
arg_resolv_conf = settings->resolv_conf;
return 0;
}