From b494d2ddf769220da1ef75fd24275ce68cdf297c Mon Sep 17 00:00:00 2001 From: Serge Hallyn Date: Fri, 27 Sep 2013 21:01:07 -0500 Subject: [PATCH] add c->may_control MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is an api function which will return false if the container is running, and the caller may not talk to its monitor over its command socket. Otherwise - if the container is not running, or the caller may access it - it returns true. We can use this in several tools early on to prevent the segvs etc which we currently get. Signed-off-by: Serge Hallyn Acked-by: Dwight Engen Acked-by: Stéphane Graber --- src/lxc/commands.c | 30 +++++++++++++++++++++++++++ src/lxc/commands.h | 1 + src/lxc/lxccontainer.c | 6 ++++++ src/lxc/lxccontainer.h | 6 ++++++ src/tests/Makefile.am | 6 ++++-- src/tests/may_control.c | 46 +++++++++++++++++++++++++++++++++++++++++ 6 files changed, 93 insertions(+), 2 deletions(-) create mode 100644 src/tests/may_control.c diff --git a/src/lxc/commands.c b/src/lxc/commands.c index 7c538c6d5..fa6e3fb49 100644 --- a/src/lxc/commands.c +++ b/src/lxc/commands.c @@ -291,6 +291,36 @@ out: return ret; } +int lxc_try_cmd(const char *name, const char *lxcpath) +{ + int stopped, ret; + struct lxc_cmd_rr cmd = { + .req = { .cmd = LXC_CMD_GET_INIT_PID }, + }; + + ret = lxc_cmd(name, &cmd, &stopped, lxcpath); + + if (stopped) + return 0; + if (ret > 0 && cmd.rsp.ret < 0) { + errno = cmd.rsp.ret; + return -1; + } + if (ret > 0) + return 0; + + /* + * At this point we weren't denied access, and the + * container *was* started. There was some inexplicable + * error in the protocol. + * I'm not clear on whether we should return -1 here, but + * we didn't receive a -EACCES, so technically it's not that + * we're not allowed to control the container - it's just not + * behaving. + */ + return 0; +} + /* Implentations of the commands and their callbacks */ /* diff --git a/src/lxc/commands.h b/src/lxc/commands.h index 2c0258ca5..7829aef22 100644 --- a/src/lxc/commands.h +++ b/src/lxc/commands.h @@ -88,5 +88,6 @@ extern int lxc_cmd_init(const char *name, struct lxc_handler *handler, const char *lxcpath); extern int lxc_cmd_mainloop_add(const char *name, struct lxc_epoll_descr *descr, struct lxc_handler *handler); +extern int lxc_try_cmd(const char *name, const char *lxcpath); #endif /* __commands_h */ diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c index 3a2ae92a4..02126b22f 100644 --- a/src/lxc/lxccontainer.c +++ b/src/lxc/lxccontainer.c @@ -2592,6 +2592,11 @@ static bool lxcapi_snapshot_restore(struct lxc_container *c, char *snapname, cha return b; } +static bool lxcapi_may_control(struct lxc_container *c) +{ + return lxc_try_cmd(c->name, c->config_path) == 0; +} + static int lxcapi_attach_run_waitl(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char *arg, ...) { va_list ap; @@ -2711,6 +2716,7 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath c->snapshot = lxcapi_snapshot; c->snapshot_list = lxcapi_snapshot_list; c->snapshot_restore = lxcapi_snapshot_restore; + c->may_control = lxcapi_may_control; /* we'll allow the caller to update these later */ if (lxc_log_init(NULL, "none", NULL, "lxc_container", 0, c->config_path)) { diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h index 225fb3995..20ab8e870 100644 --- a/src/lxc/lxccontainer.h +++ b/src/lxc/lxccontainer.h @@ -223,6 +223,12 @@ struct lxc_container { * Returns true on success, false on failure. */ bool (*snapshot_restore)(struct lxc_container *c, char *snapname, char *newname); + + /* + * Return false if there is a control socket for the container monitor, + * and the caller may not access it. Return true otherwise. + */ + bool (*may_control)(struct lxc_container *c); }; struct lxc_snapshot { diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am index 815740746..479faccdf 100644 --- a/src/tests/Makefile.am +++ b/src/tests/Makefile.am @@ -19,6 +19,7 @@ lxc_usernic_test_SOURCES = ../lxc/lxc_user_nic.c ../lxc/nl.c lxc_usernic_test_CFLAGS = -DISTEST lxc_test_snapshot_SOURCES = snapshot.c lxc_test_concurrent_SOURCES = concurrent.c +lxc_test_may_control_SOURCES = may_control.c AM_CFLAGS=-I$(top_srcdir)/src \ -DLXCROOTFSMOUNT=\"$(LXCROOTFSMOUNT)\" \ @@ -31,7 +32,7 @@ bin_PROGRAMS = lxc-test-containertests lxc-test-locktests lxc-test-startone \ lxc-test-destroytest lxc-test-saveconfig lxc-test-createtest \ lxc-test-shutdowntest lxc-test-get_item lxc-test-getkeys lxc-test-lxcpath \ lxc-test-cgpath lxc-test-clonetest lxc-test-console lxc-usernic-test \ - lxc-test-snapshot lxc-test-concurrent + lxc-test-snapshot lxc-test-concurrent lxc-test-may-control bin_SCRIPTS = lxc-test-usernic @@ -53,4 +54,5 @@ EXTRA_DIST = \ console.c \ lxc-test-usernic \ snapshot.c \ - concurrent.c + concurrent.c \ + may_control.c diff --git a/src/tests/may_control.c b/src/tests/may_control.c new file mode 100644 index 000000000..bb0178e70 --- /dev/null +++ b/src/tests/may_control.c @@ -0,0 +1,46 @@ +/* control.c + * + * Copyright © 2013 Canonical, Inc + * Author: Serge Hallyn + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2, as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include +#include +#include + +void usage(char *me) +{ + printf("Usage: %s name [lxcpath]\n", me); + exit(0); +} + +int main(int argc, char *argv[]) +{ + char *lxcpath = NULL, *name; + bool may = false; + struct lxc_container *c; + + if (argc < 2) + usage(argv[0]); + name = argv[1]; + if (argc == 3) + lxcpath = argv[2]; + c = lxc_container_new(name, lxcpath); + if (c) + may = c->may_control(c); + printf("You may%s control %s\n", may ? "" : " not", name); + exit(may ? 0 : 1); +}