[lxc-devel] [PATCH 11/24] Don't hard depend on capability.h and libcap
Stéphane Graber
stgraber at ubuntu.com
Tue Jan 8 17:03:01 UTC 2013
In the effort to make LXC work with non-standard Linux distros, this change
allows for the user to build LXC without capability support through a new
--disable-capabilities option to configure.
This effectively will cause LXC not to link against libcap and will turn all
the _cap_ functions into no-ops.
Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
configure.ac | 27 +++++++++++++++++----------
src/lxc/caps.c | 6 +++++-
src/lxc/caps.h | 24 ++++++++++++++++++++++++
src/lxc/conf.c | 11 ++++++++++-
src/lxc/start.c | 15 ++++++++++++++-
5 files changed, 70 insertions(+), 13 deletions(-)
diff --git a/configure.ac b/configure.ac
index ea98f02..22b45cd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -180,17 +180,24 @@ AC_CHECK_HEADERS([linux/unistd.h linux/netlink.h linux/genetlink.h],
AC_MSG_ERROR([Please install the Linux kernel headers.]),
[#include <sys/socket.h>])
+# Allow disabling libcap support
+AC_ARG_ENABLE([capabilities],
+ [AC_HELP_STRING([--disable-capabilities], [disable kernel capabilities])],
+ [], [enable_capabilities=yes])
+
# Check for libcap support
-AC_CHECK_HEADERS([sys/capability.h], [], AC_MSG_ERROR([Please install the libcap development files.]),
-[#include <sys/types.h>
-#include <sys/capability.h>])
-AC_CHECK_LIB(cap,cap_set_proc,caplib=yes,caplib=no)
-AC_MSG_CHECKING([linux capabilities])
-if test "x$caplib" = "xyes" ; then
- CAP_LIBS="-lcap"
- AC_MSG_RESULT([$CAP_LIBS])
+if test "x$enable_capabilities" = "xyes"; then
+ AC_CHECK_LIB(cap,cap_set_proc,caplib=yes,caplib=no)
+ AC_MSG_CHECKING([linux capabilities])
+ if test "x$caplib" = "xyes" ; then
+ CAP_LIBS="-lcap"
+ AC_MSG_RESULT([$CAP_LIBS])
+ else
+ AC_MSG_RESULT([no])
+ AC_MSG_ERROR([You are missing libcap support. If you really want to build without kernel capabilities, use --disable-capabilities])
+ fi
else
- AC_MSG_ERROR([not found])
+ CAP_LIBS=""
fi
AC_SUBST([CAP_LIBS])
@@ -214,7 +221,7 @@ AM_CONDITIONAL([IS_BIONIC], [test "x$is_bionic" = "xyes"])
AC_CHECK_DECLS([PR_CAPBSET_DROP], [], [], [#include <sys/prctl.h>])
# Check for some headers
-AC_CHECK_HEADERS([sys/signalfd.h pty.h])
+AC_CHECK_HEADERS([sys/signalfd.h pty.h sys/capability.h])
# Check for some functions
AC_CHECK_FUNCS([getline fgetln openpty])
diff --git a/src/lxc/caps.c b/src/lxc/caps.c
index 94c134d..53c552b 100644
--- a/src/lxc/caps.c
+++ b/src/lxc/caps.c
@@ -27,13 +27,16 @@
#include <stdlib.h>
#include <limits.h>
#include <sys/prctl.h>
-#include <sys/capability.h>
#include <errno.h>
+#include "config.h"
#include "log.h"
lxc_log_define(lxc_caps, lxc);
+#if HAVE_SYS_CAPABILITY_H
+#include <sys/capability.h>
+
int lxc_caps_reset(void)
{
cap_t cap = cap_init();
@@ -258,3 +261,4 @@ int lxc_caps_check(void)
return 1;
}
+#endif
diff --git a/src/lxc/caps.h b/src/lxc/caps.h
index 88cf09e..dc3fd6f 100644
--- a/src/lxc/caps.h
+++ b/src/lxc/caps.h
@@ -20,9 +20,12 @@
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
+#include "config.h"
+
#ifndef _caps_h
#define _caps_h
+#if HAVE_SYS_CAPABILITY_H
extern int lxc_caps_reset(void);
extern int lxc_caps_down(void);
extern int lxc_caps_up(void);
@@ -30,6 +33,27 @@ extern int lxc_caps_init(void);
extern int lxc_caps_check(void);
extern int lxc_caps_last_cap(void);
+#else
+static inline int lxc_caps_reset(void) {
+ return 0;
+}
+static inline int lxc_caps_down(void) {
+ return 0;
+}
+static inline int lxc_caps_up(void) {
+ return 0;
+}
+static inline int lxc_caps_init(void) {
+ return 0;
+}
+static inline int lxc_caps_check(void) {
+ return 1;
+}
+
+static inline int lxc_caps_last_cap(void) {
+ return 0;
+}
+#endif
#define lxc_priv(__lxc_function) \
({ \
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 49bba2a..25b75d7 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -48,7 +48,6 @@
#include <sys/mount.h>
#include <sys/mman.h>
#include <sys/prctl.h>
-#include <sys/capability.h>
#include <sys/personality.h>
#include <arpa/inet.h>
@@ -71,6 +70,10 @@
#include <apparmor.h>
#endif
+#if HAVE_SYS_CAPABILITY_H
+#include <sys/capability.h>
+#endif
+
#include "lxcseccomp.h"
lxc_log_define(lxc_conf, lxc);
@@ -104,6 +107,7 @@ lxc_log_define(lxc_conf, lxc);
#define MS_STRICTATIME (1 << 24)
#endif
+#if HAVE_SYS_CAPABILITY_H
#ifndef CAP_SETFCAP
#define CAP_SETFCAP 31
#endif
@@ -115,6 +119,7 @@ lxc_log_define(lxc_conf, lxc);
#ifndef CAP_MAC_ADMIN
#define CAP_MAC_ADMIN 33
#endif
+#endif
#ifndef PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
@@ -199,6 +204,7 @@ static struct mount_opt mount_opt[] = {
{ NULL, 0, 0 },
};
+#if HAVE_SYS_CAPABILITY_H
static struct caps_opt caps_opt[] = {
{ "chown", CAP_CHOWN },
{ "dac_override", CAP_DAC_OVERRIDE },
@@ -245,6 +251,9 @@ static struct caps_opt caps_opt[] = {
{ "wake_alarm", CAP_WAKE_ALARM },
#endif
};
+#else
+static struct caps_opt caps_opt[] = {};
+#endif
static int run_buffer(char *buffer)
{
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 3452022..271764e 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -41,12 +41,15 @@
#include <sys/socket.h>
#include <sys/prctl.h>
#include <sys/types.h>
-#include <sys/capability.h>
#include <sys/wait.h>
#include <sys/un.h>
#include <sys/poll.h>
#include <sys/syscall.h>
+#if HAVE_SYS_CAPABILITY_H
+#include <sys/capability.h>
+#endif
+
#ifdef HAVE_SYS_SIGNALFD_H
# include <sys/signalfd.h>
#else
@@ -339,10 +342,14 @@ int lxc_poll(const char *name, struct lxc_handler *handler)
}
if (handler->conf->need_utmp_watch) {
+ #if HAVE_SYS_CAPABILITY_H
if (lxc_utmp_mainloop_add(&descr, handler)) {
ERROR("failed to add utmp handler to mainloop");
goto out_mainloop_open;
}
+ #else
+ DEBUG("Can't start utmp handler as capabilities aren't supported\n");
+ #endif
}
return lxc_mainloop(&descr);
@@ -553,6 +560,7 @@ static int do_start(void *data)
if (lxc_sync_barrier_parent(handler, LXC_SYNC_CONFIGURE))
return -1;
+ #if HAVE_SYS_CAPABILITY_H
if (handler->conf->need_utmp_watch) {
if (prctl(PR_CAPBSET_DROP, CAP_SYS_BOOT, 0, 0, 0)) {
SYSERROR("failed to remove CAP_SYS_BOOT capability");
@@ -560,6 +568,7 @@ static int do_start(void *data)
}
DEBUG("Dropped cap_sys_boot\n");
}
+ #endif
/* Setup the container, ip, names, utsname, ... */
if (lxc_setup(handler->name, handler->conf)) {
@@ -752,7 +761,11 @@ int __lxc_start(const char *name, struct lxc_conf *conf,
handler->data = data;
if (must_drop_cap_sys_boot()) {
+ #if HAVE_SYS_CAPABILITY_H
DEBUG("Dropping cap_sys_boot\n");
+ #else
+ DEBUG("Can't drop cap_sys_boot as capabilities aren't supported\n");
+ #endif
} else {
DEBUG("Not dropping cap_sys_boot or watching utmp\n");
handler->conf->need_utmp_watch = 0;
--
1.8.0
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