src/lxc/cgroup.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <dlezcano at fr.ibm.com>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  22  */
  23 #define _GNU_SOURCE
  24 #include <stdio.h>
  25 #undef _GNU_SOURCE
  26 #include <stdlib.h>
  27 #include <errno.h>
  28 #include <mntent.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31 #include <fcntl.h>
  32 #include <sys/types.h>
  33 #include <sys/stat.h>
  34 #include <sys/param.h>
  35 #include <sys/inotify.h>
  36 #include <netinet/in.h>
  37 #include <net/if.h>
  38
  39 #include "error.h"
  40 #include <lxc/lxc.h>
  41
  42 #define MTAB "/etc/mtab"
  43
  44 static int get_cgroup_mount(const char *mtab, char *mnt)
  45 {
  46         struct mntent *mntent;
  47         FILE *file = NULL;
  48         int err = -1;
  49
  50         file = setmntent(mtab, "r");
  51         if (!file) {
  52                 lxc_log_syserror("failed to open %s", mtab);
  53                 goto out;
  54         }
  55
  56         while ((mntent = getmntent(file))) {
  57                 if (strcmp(mntent->mnt_type, "cgroup"))
  58                         continue;
  59                 strcpy(mnt, mntent->mnt_dir);
  60                 err = 0;
  61                 break;
  62         };
  63
  64         fclose(file);
  65 out:
  66         return err;
  67 }
  68
  69 int lxc_link_nsgroup(const char *name, pid_t pid)
  70 {
  71         char lxc[MAXPATHLEN];
  72         char nsgroup[MAXPATHLEN];
  73         char cgroup[MAXPATHLEN];
  74         int ret;
  75
  76         if (get_cgroup_mount(MTAB, cgroup)) {
  77                 lxc_log_info("cgroup is not mounted");
  78                 return -1;
  79         }
  80
  81         snprintf(lxc, MAXPATHLEN, LXCPATH "/%s/nsgroup", name);
  82         snprintf(nsgroup, MAXPATHLEN, "%s/%d", cgroup, pid);
  83
  84         unlink(lxc);
  85         ret = symlink(nsgroup, lxc);
  86         if (ret)
  87                 lxc_log_syserror("failed to create symlink %s->%s",
  88                                  nsgroup, lxc);
  89       return ret;
  90 }
  91
  92 int lxc_unlink_nsgroup(const char *name)
  93 {
  94         char nsgroup[MAXPATHLEN];
  95
  96         snprintf(nsgroup, MAXPATHLEN, LXCPATH "/%s/nsgroup", name);
  97         return unlink(nsgroup);
  98 }
  99
 100 int lxc_cgroup_set(const char *name, const char *subsystem, const char *value)
 101 {
 102         int fd, ret = -LXC_ERROR_INTERNAL;;
 103         char path[MAXPATHLEN];
 104
 105         snprintf(path, MAXPATHLEN, LXCPATH "/%s/nsgroup/%s", name, subsystem);
 106
 107         fd = open(path, O_WRONLY);
 108         if (fd < 0)
 109                 return -1;
 110
 111         if (write(fd, value, strlen(value)) < 0)
 112                 goto out;
 113
 114         ret = 0;
 115 out:
 116         close(fd);
 117         return ret;
 118 }
 119
 120 int lxc_cgroup_get(const char *name, const char *subsystem,
 121                    char *value, size_t len)
 122 {
 123         int fd, ret = -LXC_ERROR_INTERNAL;
 124         char path[MAXPATHLEN];
 125
 126         snprintf(path, MAXPATHLEN, LXCPATH "/%s/nsgroup/%s", name, subsystem);
 127
 128         fd = open(path, O_RDONLY);
 129         if (fd < 0)
 130                 return -1;
 131
 132         if (read(fd, value, len) < 0)
 133                 goto out;
 134
 135         ret = 0;
 136 out:
 137         close(fd);
 138         return ret;
 139 }