lib/fs.c

   1 /*
   2  * fs.c         filesystem APIs
   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  * Authors:     David Ahern <dsa@cumulusnetworks.com>
  10  *
  11  */
  12
  13 #include <sys/types.h>
  14 #include <sys/stat.h>
  15 #include <sys/socket.h>
  16 #include <sys/mount.h>
  17 #include <fcntl.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include <string.h>
  22 #include <errno.h>
  23 #include <limits.h>
  24
  25 #include "utils.h"
  26
  27 #define CGROUP2_FS_NAME "cgroup2"
  28
  29 /* if not already mounted cgroup2 is mounted here for iproute2's use */
  30 #define MNT_CGRP2_PATH  "/var/run/cgroup2"
  31
  32 /* return mount path of first occurrence of given fstype */
  33 static char *find_fs_mount(const char *fs_to_find)
  34 {
  35         char path[4096];
  36         char fstype[128];    /* max length of any filesystem name */
  37         char *mnt = NULL;
  38         FILE *fp;
  39
  40         fp = fopen("/proc/mounts", "r");
  41         if (!fp) {
  42                 fprintf(stderr,
  43                         "Failed to open mounts file: %s\n", strerror(errno));
  44                 return NULL;
  45         }
  46
  47         while (fscanf(fp, "%*s %4096s %127s %*s %*d %*d\n",
  48                       path, fstype) == 2) {
  49                 if (strcmp(fstype, fs_to_find) == 0) {
  50                         mnt = strdup(path);
  51                         break;
  52                 }
  53         }
  54
  55         fclose(fp);
  56
  57         return mnt;
  58 }
  59
  60 /* caller needs to free string returned */
  61 char *find_cgroup2_mount(void)
  62 {
  63         char *mnt = find_fs_mount(CGROUP2_FS_NAME);
  64
  65         if (mnt)
  66                 return mnt;
  67
  68         mnt = strdup(MNT_CGRP2_PATH);
  69         if (!mnt) {
  70                 fprintf(stderr, "Failed to allocate memory for cgroup2 path\n");
  71                 return NULL;
  72
  73         }
  74
  75         if (make_path(mnt, 0755)) {
  76                 fprintf(stderr, "Failed to setup vrf cgroup2 directory\n");
  77                 free(mnt);
  78                 return NULL;
  79         }
  80
  81         if (mount("none", mnt, CGROUP2_FS_NAME, 0, NULL)) {
  82                 /* EBUSY means already mounted */
  83                 if (errno == EBUSY)
  84                         goto out;
  85
  86                 if (errno == ENODEV) {
  87                         fprintf(stderr,
  88                                 "Failed to mount cgroup2. Are CGROUPS enabled in your kernel?\n");
  89                 } else {
  90                         fprintf(stderr,
  91                                 "Failed to mount cgroup2: %s\n",
  92                                 strerror(errno));
  93                 }
  94                 free(mnt);
  95                 return NULL;
  96         }
  97 out:
  98         return mnt;
  99 }
 100
 101 int make_path(const char *path, mode_t mode)
 102 {
 103         char *dir, *delim;
 104         struct stat sbuf;
 105         int rc = -1;
 106
 107         delim = dir = strdup(path);
 108         if (dir == NULL) {
 109                 fprintf(stderr, "strdup failed copying path");
 110                 return -1;
 111         }
 112
 113         /* skip '/' -- it had better exist */
 114         if (*delim == '/')
 115                 delim++;
 116
 117         while (1) {
 118                 delim = strchr(delim, '/');
 119                 if (delim)
 120                         *delim = '\0';
 121
 122                 if (stat(dir, &sbuf) != 0) {
 123                         if (errno != ENOENT) {
 124                                 fprintf(stderr,
 125                                         "stat failed for %s: %s\n",
 126                                         dir, strerror(errno));
 127                                 goto out;
 128                         }
 129
 130                         if (mkdir(dir, mode) != 0) {
 131                                 fprintf(stderr,
 132                                         "mkdir failed for %s: %s\n",
 133                                         dir, strerror(errno));
 134                                 goto out;
 135                         }
 136                 }
 137
 138                 if (delim == NULL)
 139                         break;
 140
 141                 *delim = '/';
 142                 delim++;
 143                 if (*delim == '\0')
 144                         break;
 145         }
 146         rc = 0;
 147 out:
 148         free(dir);
 149
 150         return rc;
 151 }