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 <ctype.h>
  18 #include <fcntl.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23 #ifdef HAVE_LIBBSD
  24 #include <bsd/string.h>
  25 #endif
  26 #include <errno.h>
  27 #include <limits.h>
  28
  29 #include "utils.h"
  30
  31 #define CGROUP2_FS_NAME "cgroup2"
  32
  33 /* if not already mounted cgroup2 is mounted here for iproute2's use */
  34 #define MNT_CGRP2_PATH  "/var/run/cgroup2"
  35
  36 /* return mount path of first occurrence of given fstype */
  37 static char *find_fs_mount(const char *fs_to_find)
  38 {
  39         char path[4096];
  40         char fstype[128];    /* max length of any filesystem name */
  41         char *mnt = NULL;
  42         FILE *fp;
  43
  44         fp = fopen("/proc/mounts", "r");
  45         if (!fp) {
  46                 fprintf(stderr,
  47                         "Failed to open mounts file: %s\n", strerror(errno));
  48                 return NULL;
  49         }
  50
  51         while (fscanf(fp, "%*s %4095s %127s %*s %*d %*d\n",
  52                       path, fstype) == 2) {
  53                 if (strcmp(fstype, fs_to_find) == 0) {
  54                         mnt = strdup(path);
  55                         break;
  56                 }
  57         }
  58
  59         fclose(fp);
  60
  61         return mnt;
  62 }
  63
  64 /* caller needs to free string returned */
  65 char *find_cgroup2_mount(void)
  66 {
  67         char *mnt = find_fs_mount(CGROUP2_FS_NAME);
  68
  69         if (mnt)
  70                 return mnt;
  71
  72         mnt = strdup(MNT_CGRP2_PATH);
  73         if (!mnt) {
  74                 fprintf(stderr, "Failed to allocate memory for cgroup2 path\n");
  75                 return NULL;
  76
  77         }
  78
  79         if (make_path(mnt, 0755)) {
  80                 fprintf(stderr, "Failed to setup vrf cgroup2 directory\n");
  81                 free(mnt);
  82                 return NULL;
  83         }
  84
  85         if (mount("none", mnt, CGROUP2_FS_NAME, 0, NULL)) {
  86                 /* EBUSY means already mounted */
  87                 if (errno == EBUSY)
  88                         goto out;
  89
  90                 if (errno == ENODEV) {
  91                         fprintf(stderr,
  92                                 "Failed to mount cgroup2. Are CGROUPS enabled in your kernel?\n");
  93                 } else {
  94                         fprintf(stderr,
  95                                 "Failed to mount cgroup2: %s\n",
  96                                 strerror(errno));
  97                 }
  98                 free(mnt);
  99                 return NULL;
 100         }
 101 out:
 102         return mnt;
 103 }
 104
 105 int make_path(const char *path, mode_t mode)
 106 {
 107         char *dir, *delim;
 108         int rc = -1;
 109
 110         delim = dir = strdup(path);
 111         if (dir == NULL) {
 112                 fprintf(stderr, "strdup failed copying path");
 113                 return -1;
 114         }
 115
 116         /* skip '/' -- it had better exist */
 117         if (*delim == '/')
 118                 delim++;
 119
 120         while (1) {
 121                 delim = strchr(delim, '/');
 122                 if (delim)
 123                         *delim = '\0';
 124
 125                 rc = mkdir(dir, mode);
 126                 if (mkdir(dir, mode) != 0 && errno != EEXIST) {
 127                         fprintf(stderr, "mkdir failed for %s: %s\n",
 128                                 dir, strerror(errno));
 129                         goto out;
 130                 }
 131
 132                 if (delim == NULL)
 133                         break;
 134
 135                 *delim = '/';
 136                 delim++;
 137                 if (*delim == '\0')
 138                         break;
 139         }
 140         rc = 0;
 141 out:
 142         free(dir);
 143
 144         return rc;
 145 }
 146
 147 int get_command_name(const char *pid, char *comm, size_t len)
 148 {
 149         char path[PATH_MAX];
 150         char line[128];
 151         FILE *fp;
 152
 153         if (snprintf(path, sizeof(path),
 154                      "/proc/%s/status", pid) >= sizeof(path)) {
 155                 return -1;
 156         }
 157
 158         fp = fopen(path, "r");
 159         if (!fp)
 160                 return -1;
 161
 162         comm[0] = '\0';
 163         while (fgets(line, sizeof(line), fp)) {
 164                 char *nl, *name;
 165
 166                 name = strstr(line, "Name:");
 167                 if (!name)
 168                         continue;
 169
 170                 name += 5;
 171                 while (isspace(*name))
 172                         name++;
 173
 174                 nl = strchr(name, '\n');
 175                 if (nl)
 176                         *nl = '\0';
 177
 178                 strlcpy(comm, name, len);
 179                 break;
 180         }
 181
 182         fclose(fp);
 183
 184         return 0;
 185 }