tests/ln/tests_for_do_link.c

#include "../../unity/unity.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdbool.h>
#include <dirent.h>

/* The following globals and function are defined in the ln source prior to this include:
   - static bool do_link(...)
   - static enum backup_type backup_type;
   - static bool symbolic_link, relative, logical, interactive, remove_existing_files,
     verbose, hard_dir_link, beware_hard_dir_link, dereference_dest_dir_symlinks;
   - static Hash_table *dest_set;
   They are accessible here since this file is included into the same translation unit.
*/

static char *path_join2(const char *a, const char *b) {
  size_t la = strlen(a);
  size_t lb = strlen(b);
  int need_slash = (la > 0 && a[la-1] != '/');
  size_t len = la + (need_slash ? 1 : 0) + lb + 1;
  char *out = (char*)malloc(len);
  if (!out) return NULL;
  memcpy(out, a, la);
  if (need_slash) out[la++] = '/';
  memcpy(out + la, b, lb);
  out[la + lb] = '\0';
  return out;
}

static char *mkdtemp_wrap(void) {
  char tmpl[PATH_MAX];
  const char *tmpdir = getenv("TMPDIR");
  if (!tmpdir || !*tmpdir) tmpdir = "/tmp";
  snprintf(tmpl, sizeof(tmpl), "%s/ln_do_link_test_%ld_XXXXXX", tmpdir, (long)getpid());
  char *buf = strdup(tmpl);
  if (!buf) return NULL;
  if (!mkdtemp(buf)) {
    free(buf);
    return NULL;
  }
  return buf;
}

static int write_file(const char *path, const char *data) {
  int fd = open(path, O_CREAT | O_WRONLY | O_TRUNC, 0644);
  if (fd < 0) return -1;
  size_t len = strlen(data);
  ssize_t wr = write(fd, data, len);
  int e = 0;
  if (wr < 0 || (size_t)wr != len) e = -1;
  if (close(fd) != 0) e = -1;
  return e;
}

static int open_dirfd(const char *dir) {
  int fd = open(dir, O_RDONLY
#ifdef O_DIRECTORY
                | O_DIRECTORY
#endif
#ifdef O_CLOEXEC
                | O_CLOEXEC
#endif
                );
  return fd;
}

static char *realpath_dup(const char *p) {
  char buf[PATH_MAX];
  if (!realpath(p, buf)) return NULL;
  return strdup(buf);
}

/* Resolve the symlink text as it would be interpreted from dest_dir. */
static char *resolve_link_from_dir(const char *dest_dir, const char *link_text) {
  char *abs = NULL;
  if (link_text[0] == '/') {
    abs = realpath_dup(link_text);
  } else {
    char *joined = path_join2(dest_dir, link_text);
    if (!joined) return NULL;
    abs = realpath_dup(joined);
    free(joined);
  }
  return abs;
}

/* Reset all relevant ln flags and state to a known baseline. */
static void reset_ln_flags(void) {
  symbolic_link = false;
  relative = false;
  logical = !!LINK_FOLLOWS_SYMLINKS; /* use default as baseline; individual tests can set explicitly */
  interactive = false;
  remove_existing_files = false;
  verbose = false;
  hard_dir_link = false;
  beware_hard_dir_link = false;
  dereference_dest_dir_symlinks = true;
  backup_type = no_backups;
  dest_set = NULL;
}

void setUp(void) {
  /* Nothing global to set here; tests call reset_ln_flags explicitly. */
}
void tearDown(void) {
  /* Each test cleans up its own files/directories. */
}

/* Test: simple hard link creation when destination does not exist. */
void test_do_link_hardlink_simple(void) {
  reset_ln_flags();
  logical = 0; /* physical by default */

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  char *src = path_join2(td, "src.txt");
  TEST_ASSERT_NOT_NULL(src);
  TEST_ASSERT_EQUAL_INT(0, write_file(src, "hello"));

  char *dest_dir = td; /* place link in same directory */
  char *dest_full = path_join2(dest_dir, "dest.hard");
  TEST_ASSERT_NOT_NULL(dest_full);
  char *slash = strrchr(dest_full, '/');
  TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(dest_dir);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(src, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_TRUE(ok);

  struct stat ss, ds;
  TEST_ASSERT_EQUAL_INT(0, stat(src, &ss));
  TEST_ASSERT_EQUAL_INT(0, stat(dest_full, &ds));
  TEST_ASSERT_EQUAL_UINT64(ss.st_ino, ds.st_ino);
  TEST_ASSERT_EQUAL_INT(ss.st_dev, ds.st_dev);

  close(dfd);
  unlink(dest_full);
  unlink(src);
  rmdir(td);
  free(dest_full);
  free(src);
  free(td);
}

/* Test: simple symlink creation with absolute target (non-relative). */
void test_do_link_symlink_absolute(void) {
  reset_ln_flags();
  symbolic_link = true;
  relative = false;

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  char *src = path_join2(td, "src.txt");
  TEST_ASSERT_NOT_NULL(src);
  TEST_ASSERT_EQUAL_INT(0, write_file(src, "world"));

  char *dest_full = path_join2(td, "dest.sym");
  TEST_ASSERT_NOT_NULL(dest_full);
  char *slash = strrchr(dest_full, '/');
  TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(td);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(src, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_TRUE(ok);

  char buf[PATH_MAX];
  ssize_t n = readlink(dest_full, buf, sizeof(buf)-1);
  TEST_ASSERT_TRUE(n >= 0);
  buf[n] = '\0';
  TEST_ASSERT_EQUAL_STRING(src, buf);

  close(dfd);
  unlink(dest_full);
  unlink(src);
  rmdir(td);
  free(dest_full);
  free(src);
  free(td);
}

/* Test: relative symlink creation (-r) and that it resolves to the correct absolute path. */
void test_do_link_symlink_relative_resolves(void) {
  reset_ln_flags();
  symbolic_link = true;
  relative = true;

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  /* Create source in td/a/srcdir/s.txt and dest in td/b/destdir/l.lnk */
  char *a = path_join2(td, "a");
  char *b = path_join2(td, "b");
  char *srcdir = path_join2(a, "srcdir");
  char *destdir = path_join2(b, "destdir");
  TEST_ASSERT_EQUAL_INT(0, mkdir(a, 0700));
  TEST_ASSERT_EQUAL_INT(0, mkdir(b, 0700));
  TEST_ASSERT_EQUAL_INT(0, mkdir(srcdir, 0700));
  TEST_ASSERT_EQUAL_INT(0, mkdir(destdir, 0700));

  char *src = path_join2(srcdir, "s.txt");
  TEST_ASSERT_NOT_NULL(src);
  TEST_ASSERT_EQUAL_INT(0, write_file(src, "data"));

  char *dest_full = path_join2(destdir, "l.lnk");
  TEST_ASSERT_NOT_NULL(dest_full);
  char *slash = strrchr(dest_full, '/'); TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(destdir);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(src, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_TRUE(ok);

  /* Read link text and ensure it resolves to the same abs path as src */
  char linkbuf[PATH_MAX];
  ssize_t n = readlink(dest_full, linkbuf, sizeof(linkbuf)-1);
  TEST_ASSERT_TRUE(n >= 0);
  linkbuf[n] = '\0';

  char *src_abs = realpath_dup(src);
  TEST_ASSERT_NOT_NULL(src_abs);
  char *resolved = resolve_link_from_dir(destdir, linkbuf);
  TEST_ASSERT_NOT_NULL(resolved);
  TEST_ASSERT_EQUAL_STRING(src_abs, resolved);

  close(dfd);

  /* Cleanup */
  unlink(dest_full);
  unlink(src);
  rmdir(destdir);
  rmdir(srcdir);
  rmdir(b);
  rmdir(a);
  rmdir(td);

  free(resolved);
  free(src_abs);
  free(dest_full);
  free(src);
  free(destdir);
  free(srcdir);
  free(b);
  free(a);
  free(td);
}

/* Test: force overwrite existing destination (-f). */
void test_do_link_force_overwrite(void) {
  reset_ln_flags();
  symbolic_link = false;
  remove_existing_files = true;
  logical = 0;

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  char *src = path_join2(td, "src.txt");
  char *dest_full = path_join2(td, "dest.txt");
  TEST_ASSERT_NOT_NULL(src && dest_full);

  TEST_ASSERT_EQUAL_INT(0, write_file(src, "new"));
  TEST_ASSERT_EQUAL_INT(0, write_file(dest_full, "old"));

  char *slash = strrchr(dest_full, '/'); TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(td);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(src, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_TRUE(ok);

  struct stat ss, ds;
  TEST_ASSERT_EQUAL_INT(0, stat(src, &ss));
  TEST_ASSERT_EQUAL_INT(0, stat(dest_full, &ds));
  TEST_ASSERT_EQUAL_UINT64(ss.st_ino, ds.st_ino);
  TEST_ASSERT_EQUAL_INT(ss.st_dev, ds.st_dev);

  close(dfd);
  unlink(dest_full);
  unlink(src);
  rmdir(td);
  free(dest_full);
  free(src);
  free(td);
}

/* Test: hard link to a directory is disallowed unless hard_dir_link is true. */
void test_do_link_hardlink_directory_disallowed(void) {
  reset_ln_flags();
  symbolic_link = false;
  hard_dir_link = false;

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  char *srcdir = path_join2(td, "adir");
  char *dest_full = path_join2(td, "dest_dir_hard");
  TEST_ASSERT_NOT_NULL(srcdir && dest_full);
  TEST_ASSERT_EQUAL_INT(0, mkdir(srcdir, 0700));

  char *slash = strrchr(dest_full, '/'); TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(td);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(srcdir, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_FALSE(ok);

  /* Ensure destination was not created (should not exist) */
  struct stat st;
  TEST_ASSERT_EQUAL_INT(-1, lstat(dest_full, &st));
  TEST_ASSERT_EQUAL_INT(ENOENT, errno);

  close(dfd);
  rmdir(srcdir);
  rmdir(td);
  free(dest_full);
  free(srcdir);
  free(td);
}

/* Test: prevent self-overwrite when source and dest are the same entry with -f. */
void test_do_link_same_file_protection(void) {
  reset_ln_flags();
  symbolic_link = false;
  remove_existing_files = true; /* required to trigger the self-same check */

  char *td = mkdtemp_wrap();
  TEST_ASSERT_NOT_NULL(td);

  char *path = path_join2(td, "same.txt");
  TEST_ASSERT_NOT_NULL(path);
  TEST_ASSERT_EQUAL_INT(0, write_file(path, "x"));

  /* dest is the same as source */
  char *dest_full = strdup(path);
  TEST_ASSERT_NOT_NULL(dest_full);
  char *slash = strrchr(dest_full, '/'); TEST_ASSERT_NOT_NULL(slash);
  char *dest_base = slash + 1;

  int dfd = open_dirfd(td);
  TEST_ASSERT_TRUE(dfd >= 0);

  bool ok = do_link(path, dfd, dest_base, dest_full, -1);
  TEST_ASSERT_FALSE(ok);

  close(dfd);
  unlink(path);
  rmdir(td);
  free(dest_full);
  free(path);
  free(td);
}

int main(void) {
  UNITY_BEGIN();

  RUN_TEST(test_do_link_hardlink_simple);
  RUN_TEST(test_do_link_symlink_absolute);
  RUN_TEST(test_do_link_symlink_relative_resolves);
  RUN_TEST(test_do_link_force_overwrite);
  RUN_TEST(test_do_link_hardlink_directory_disallowed);
  RUN_TEST(test_do_link_same_file_protection);

  return UNITY_END();
}