lib/namespace.c

   1 /*
   2  * namespace.c
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  */
   9
  10 #include <sys/statvfs.h>
  11 #include <fcntl.h>
  12 #include <dirent.h>
  13 #include <limits.h>
  14
  15 #include "utils.h"
  16 #include "namespace.h"
  17
  18 static void bind_etc(const char *name)
  19 {
  20         char etc_netns_path[sizeof(NETNS_ETC_DIR) + NAME_MAX];
  21         char netns_name[PATH_MAX];
  22         char etc_name[PATH_MAX];
  23         struct dirent *entry;
  24         DIR *dir;
  25
  26         if (strlen(name) >= NAME_MAX)
  27                 return;
  28
  29         snprintf(etc_netns_path, sizeof(etc_netns_path), "%s/%s", NETNS_ETC_DIR, name);
  30         dir = opendir(etc_netns_path);
  31         if (!dir)
  32                 return;
  33
  34         while ((entry = readdir(dir)) != NULL) {
  35                 if (strcmp(entry->d_name, ".") == 0)
  36                         continue;
  37                 if (strcmp(entry->d_name, "..") == 0)
  38                         continue;
  39                 snprintf(netns_name, sizeof(netns_name), "%s/%s", etc_netns_path, entry->d_name);
  40                 snprintf(etc_name, sizeof(etc_name), "/etc/%s", entry->d_name);
  41                 if (mount(netns_name, etc_name, "none", MS_BIND, NULL) < 0) {
  42                         fprintf(stderr, "Bind %s -> %s failed: %s\n",
  43                                 netns_name, etc_name, strerror(errno));
  44                 }
  45         }
  46         closedir(dir);
  47 }
  48
  49 int netns_switch(char *name)
  50 {
  51         char net_path[PATH_MAX];
  52         int netns;
  53         unsigned long mountflags = 0;
  54         struct statvfs fsstat;
  55
  56         snprintf(net_path, sizeof(net_path), "%s/%s", NETNS_RUN_DIR, name);
  57         netns = open(net_path, O_RDONLY | O_CLOEXEC);
  58         if (netns < 0) {
  59                 fprintf(stderr, "Cannot open network namespace \"%s\": %s\n",
  60                         name, strerror(errno));
  61                 return -1;
  62         }
  63
  64         if (setns(netns, CLONE_NEWNET) < 0) {
  65                 fprintf(stderr, "setting the network namespace \"%s\" failed: %s\n",
  66                         name, strerror(errno));
  67                 close(netns);
  68                 return -1;
  69         }
  70         close(netns);
  71
  72         if (unshare(CLONE_NEWNS) < 0) {
  73                 fprintf(stderr, "unshare failed: %s\n", strerror(errno));
  74                 return -1;
  75         }
  76         /* Don't let any mounts propagate back to the parent */
  77         if (mount("", "/", "none", MS_SLAVE | MS_REC, NULL)) {
  78                 fprintf(stderr, "\"mount --make-rslave /\" failed: %s\n",
  79                         strerror(errno));
  80                 return -1;
  81         }
  82
  83         /* Mount a version of /sys that describes the network namespace */
  84
  85         if (statvfs("/sys", &fsstat) < 0) {
  86                 fprintf(stderr, "could not stat /sys (not mounted?): %s\n",strerror(errno));
  87                 return -1;
  88         }
  89         if (fsstat.f_flag & ST_RDONLY) {
  90                 /* If /sys is not writable (e.g. in a container), we can't
  91                  * unmount the old /sys instance, but we can still mount a new
  92                  * read-only instance over it. */
  93                 mountflags = MS_RDONLY;
  94         } else {
  95                 if (umount2("/sys", MNT_DETACH) < 0) {
  96                         fprintf(stderr, "umount of /sys failed: %s\n", strerror(errno));
  97                         return -1;
  98                 }
  99         }
 100         if (mount(name, "/sys", "sysfs", mountflags, NULL) < 0) {
 101                 fprintf(stderr, "mount of /sys failed: %s\n",strerror(errno));
 102                 return -1;
 103         }
 104
 105         /* Setup bind mounts for config files in /etc */
 106         bind_etc(name);
 107         return 0;
 108 }
 109
 110 int netns_get_fd(const char *name)
 111 {
 112         char pathbuf[PATH_MAX];
 113         const char *path, *ptr;
 114
 115         path = name;
 116         ptr = strchr(name, '/');
 117         if (!ptr) {
 118                 snprintf(pathbuf, sizeof(pathbuf), "%s/%s",
 119                         NETNS_RUN_DIR, name );
 120                 path = pathbuf;
 121         }
 122         return open(path, O_RDONLY);
 123 }
 124
 125 int netns_foreach(int (*func)(char *nsname, void *arg), void *arg)
 126 {
 127         DIR *dir;
 128         struct dirent *entry;
 129
 130         dir = opendir(NETNS_RUN_DIR);
 131         if (!dir)
 132                 return -1;
 133
 134         while ((entry = readdir(dir)) != NULL) {
 135                 if (strcmp(entry->d_name, ".") == 0)
 136                         continue;
 137                 if (strcmp(entry->d_name, "..") == 0)
 138                         continue;
 139                 if (func(entry->d_name, arg))
 140                         break;
 141         }
 142
 143         closedir(dir);
 144         return 0;
 145 }