src/lxc/namespace.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2009
   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
  24 #include <unistd.h>
  25 #include <alloca.h>
  26 #include <errno.h>
  27 #include <signal.h>
  28 #include <syscall.h>
  29 #include <sys/param.h>
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32 #include <fcntl.h>
  33
  34 #include "namespace.h"
  35 #include "log.h"
  36
  37 #include "setns.h"
  38
  39 lxc_log_define(lxc_namespace, lxc);
  40
  41 struct clone_arg {
  42         int (*fn)(void *);
  43         void *arg;
  44 };
  45
  46 int setns(int fd, int nstype)
  47 {
  48 #ifndef __NR_setns
  49         errno = ENOSYS;
  50         return -1;
  51 #else
  52         return syscall(__NR_setns, fd, nstype);
  53 #endif
  54 }
  55
  56 static int do_clone(void *arg)
  57 {
  58         struct clone_arg *clone_arg = arg;
  59         return clone_arg->fn(clone_arg->arg);
  60 }
  61
  62 pid_t lxc_clone(int (*fn)(void *), void *arg, int flags)
  63 {
  64         struct clone_arg clone_arg = {
  65                 .fn = fn,
  66                 .arg = arg,
  67         };
  68
  69         long stack_size = sysconf(_SC_PAGESIZE);
  70         void *stack = alloca(stack_size) + stack_size;
  71         pid_t ret;
  72
  73 #ifdef __ia64__
  74         ret = __clone2(do_clone, stack,
  75                        stack_size, flags | SIGCHLD, &clone_arg);
  76 #else
  77         ret = clone(do_clone, stack, flags | SIGCHLD, &clone_arg);
  78 #endif
  79         if (ret < 0)
  80                 ERROR("failed to clone(0x%x): %s", flags, strerror(errno));
  81
  82         return ret;
  83 }
  84
  85 int lxc_attach(pid_t pid)
  86 {
  87         char path[MAXPATHLEN];
  88         char *ns[] = { "pid", "mnt", "net", "ipc", "uts" };
  89         const int size = sizeof(ns) / sizeof(char *);
  90         int fd[size];
  91         int i;
  92
  93         sprintf(path, "/proc/%d/ns", pid);
  94         if (access(path, X_OK)) {
  95                 ERROR("Does this kernel version support 'attach' ?");
  96                 return -1;
  97         }
  98
  99         for (i = 0; i < size; i++) {
 100                 sprintf(path, "/proc/%d/ns/%s", pid, ns[i]);
 101                 fd[i] = open(path, O_RDONLY);
 102                 if (fd[i] < 0) {
 103                         SYSERROR("failed to open '%s'", path);
 104                         return -1;
 105                 }
 106         }
 107
 108         for (i = 0; i < size; i++) {
 109                 if (setns(fd[i], 0)) {
 110                         SYSERROR("failed to set namespace '%s'", ns[i]);
 111                         return -1;
 112                 }
 113
 114                 close(fd[i]);
 115         }
 116
 117         return 0;
 118 }