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