xattr.c

   1 #define _GNU_SOURCE
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <stdarg.h>
   5 #include <stdbool.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8 #include <errno.h>
   9 #include <dirent.h>
  10 #include <sys/types.h>
  11 #include <sys/xattr.h>
  12 #include <sys/socket.h>
  13 #include <signal.h>
  14
  15 #define ERR_USAGE       1
  16 #define ERR_SYSCALL     2
  17 #define ERR_CALL        3
  18 #define ERR_FATAL       4
  19
  20 #define ERROR(err, ...)                                                 \
  21         do {                                                            \
  22                 do_log(__FILE__, __LINE__, __FUNCTION__, __VA_ARGS__);  \
  23                 exit(err);                                              \
  24         } while (0)
  25
  26 #define LOG(...)                                                        \
  27         do {                                                            \
  28                 do_log(__FILE__, __LINE__, __FUNCTION__, __VA_ARGS__);  \
  29         } while (0)
  30
  31 #define FREE(p)                         \
  32         do {                            \
  33                 free(p);                \
  34                 p = 0;                  \
  35         } while (0)
  36
  37 static void do_log(const char *file, int line, const char *func, const char *fmt, ...)
  38 {
  39         char *message;
  40         va_list args;
  41         int len;
  42
  43         va_start(args, fmt);
  44         len = vasprintf(&message, fmt, args);
  45         va_end(args);
  46         if (len == -1) {
  47                 exit(ERR_FATAL);
  48         }
  49
  50         printf("%s:%d(%s): %s\n", file, line, func, message);
  51         free(message);
  52 }
  53
  54 static int run_child(const char *path, int fd)
  55 {
  56         ssize_t nwritten;
  57         char c;
  58         int ret;
  59
  60         c = (getpid() % 10) + 48;
  61
  62         ret = setxattr(path, "user.test", &c, 1, 0);
  63         if (ret != 0) {
  64                 ERROR(ERR_SYSCALL,
  65                       "setxattr failed: %s\n",
  66                       strerror(errno));
  67         }
  68
  69         /* Tell parent what we wrote */
  70         nwritten = write(fd, &c, 1);
  71         if (nwritten != 1) {
  72                 ERROR(ERR_SYSCALL,
  73                       "write failed: %s\n",
  74                       strerror(errno));
  75         }
  76
  77         return 0;
  78 }
  79
  80 static int run_parent(const char *path)
  81 {
  82         pid_t child;
  83         int fds[2];
  84         int child_fd;
  85         ssize_t nwritten;
  86         ssize_t nread;
  87         int ret;
  88
  89         while (true) {
  90                 char expected;
  91                 char got;
  92
  93                 ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
  94                 if (ret != 0) {
  95                         ERROR(ERR_SYSCALL, "socketpair failed: %s\n", strerror(errno));
  96                 }
  97
  98                 child = fork();
  99                 if (child == -1) {
 100                         ERROR(ERR_SYSCALL, "fork failed: %s\n", strerror(errno));
 101                 }
 102                 if (child == 0) {
 103                         close(fds[0]);
 104                         return run_child(path, fds[1]);
 105                 }
 106
 107                 close(fds[1]);
 108                 child_fd = fds[0];
 109
 110                 /* Read expected value from child */
 111                 nread = read(child_fd, &expected, 1);
 112                 if (nread != 1) {
 113                         return 0;
 114                 }
 115
 116                 /* Wait for the child to go away*/
 117                 nread = read(child_fd, &expected, 1);
 118                 if (nread != 0) {
 119                         ERROR(ERR_CALL, "Non-0 read\n");
 120                         return 0;
 121                 }
 122
 123                 usleep(10000);
 124
 125                 nread = getxattr(path, "user.test", &got, 1);
 126                 if (nread == -1) {
 127                         ERROR(ERR_SYSCALL,
 128                               "getxattr failed: %s\n",
 129                               strerror(errno));
 130                 }
 131
 132                 printf("expected: %c, got: %c\n", expected, got);
 133                 if (expected != got) {
 134                         ERROR(ERR_FATAL,
 135                               "Expected: %c, got: %c\n",
 136                               expected, got);
 137                 }
 138
 139                 close(child_fd);
 140         }
 141
 142         return 0;
 143 }
 144
 145 int main(int argc, char **argv)
 146 {
 147         char *path = NULL;
 148         struct sigaction sa;
 149         int ret;
 150
 151         if (argc != 2) {
 152                 ERROR(ERR_USAGE, "Usage: %s <PATH>\n", argv[0]);
 153         }
 154         path = argv[1];
 155
 156         sa = (struct sigaction) {
 157                 .sa_handler = SIG_IGN,
 158                 .sa_flags = SA_NOCLDWAIT,
 159         };
 160
 161         ret = sigaction(SIGCHLD, &sa, NULL);
 162         if (ret != 0) {
 163                 ERROR(ERR_SYSCALL, "sigaction failed: %s\n", strerror(errno));
 164         }
 165
 166
 167         return run_parent(path);
 168 }