Merge branch 'bug1376'

changes/bug1376

@@ -0,0 +1,4 @@
+  o Minor bugfixes:
+
+    - Added additional argument to write_chunks_to_file to optionally skip
+      using a temp file to do non-atomic writes. Implements ticket #1376.

src/common/util.c

@@ -2191,12 +2191,20 @@ write_chunks_to_file_impl(const char *fname, const smartlist_t *chunks,
   return -1;
 }
 
-/** Given a smartlist of sized_chunk_t, write them atomically to a file
+/** Given a smartlist of sized_chunk_t, write them to a file
- * <b>fname</b>, overwriting or creating the file as necessary. */
+ * <b>fname</b>, overwriting or creating the file as necessary.
+ * If <b>no_tempfile</b> is 0 then the file will be written
+ * atomically. */
 int
-write_chunks_to_file(const char *fname, const smartlist_t *chunks, int bin)
+write_chunks_to_file(const char *fname, const smartlist_t *chunks, int bin,
+                     int no_tempfile)
 {
   int flags = OPEN_FLAGS_REPLACE|(bin?O_BINARY:O_TEXT);
+
+  if (no_tempfile) {
+    /* O_APPEND stops write_chunks_to_file from using tempfiles */
+    flags |= O_APPEND;
+  }
   return write_chunks_to_file_impl(fname, chunks, flags);
 }
 

src/common/util.h

@@ -365,7 +365,7 @@ typedef struct sized_chunk_t {
   size_t len;
 } sized_chunk_t;
 int write_chunks_to_file(const char *fname, const struct smartlist_t *chunks,
-                         int bin);
+                         int bin, int no_tempfile);
 int append_bytes_to_file(const char *fname, const char *str, size_t len,
                          int bin);
 int write_bytes_to_new_file(const char *fname, const char *str, size_t len,

src/or/dirvote.c

@@ -3143,7 +3143,7 @@ dirvote_compute_consensuses(void)
     });
 
   votefile = get_datadir_fname("v3-status-votes");
-  write_chunks_to_file(votefile, votestrings, 0);
+  write_chunks_to_file(votefile, votestrings, 0, 0);
   tor_free(votefile);
   SMARTLIST_FOREACH(votestrings, sized_chunk_t *, c, tor_free(c));
   smartlist_free(votestrings);

src/or/routerlist.c

@@ -449,7 +449,7 @@ trusted_dirs_flush_certs_to_disk(void)
   } DIGESTMAP_FOREACH_END;
 
   filename = get_datadir_fname("cached-certs");
-  if (write_chunks_to_file(filename, chunks, 0)) {
+  if (write_chunks_to_file(filename, chunks, 0, 0)) {
     log_warn(LD_FS, "Error writing certificates to disk.");
   }
   tor_free(filename);
@@ -1069,7 +1069,7 @@ router_rebuild_store(int flags, desc_store_t *store)
       smartlist_add(chunk_list, c);
   } SMARTLIST_FOREACH_END(sd);
 
-  if (write_chunks_to_file(fname_tmp, chunk_list, 1)<0) {
+  if (write_chunks_to_file(fname_tmp, chunk_list, 1, 1)<0) {
     log_warn(LD_FS, "Error writing router store to disk.");
     goto done;
   }

src/test/test_util.c

@@ -102,6 +102,112 @@ test_util_read_file_eof_zero_bytes(void *arg)
   test_util_read_until_eof_impl("tor_test_fifo_empty", 0, 10000);
 }
 
+/* Test the basic expected behaviour for write_chunks_to_file.
+ * NOTE: This will need to be updated if we ever change the tempfile location
+ * or extension */
+static void
+test_util_write_chunks_to_file(void *arg)
+{
+  char *fname = NULL;
+  char *tempname = NULL;
+  char *str = NULL;
+  int r;
+  int fd = -1;
+  struct stat st;
+
+  /* These should be two different sizes to ensure the data is different
+   * between the data file and the temp file's 'known string' */
+  int temp_str_len = 1024;
+  int data_str_len = 512;
+  char *data_str = tor_malloc(data_str_len);
+  char *temp_str = tor_malloc(temp_str_len);
+
+  smartlist_t *chunks = smartlist_new();
+  sized_chunk_t c = {data_str, data_str_len/2};
+  sized_chunk_t c2 = {data_str + data_str_len/2, data_str_len/2};
+  (void)arg;
+
+  crypto_rand(temp_str, temp_str_len);
+  crypto_rand(data_str, data_str_len);
+
+  // Ensure it can write multiple chunks
+
+  smartlist_add(chunks, &c);
+  smartlist_add(chunks, &c2);
+
+  /*
+  * Check if it writes using a tempfile
+  */
+  fname = tor_strdup(get_fname("write_chunks_with_tempfile"));
+  tor_asprintf(&tempname, "%s.tmp", fname);
+
+  // write a known string to a file where the tempfile will be
+  r = write_bytes_to_file(tempname, temp_str, temp_str_len, 1);
+  tt_int_op(r, ==, 0);
+
+  // call write_chunks_to_file
+  r = write_chunks_to_file(fname, chunks, 1, 0);
+  tt_int_op(r, ==, 0);
+
+  // assert the file has been written (expected size)
+  str = read_file_to_str(fname, RFTS_BIN, &st);
+  tt_assert(str != NULL);
+  tt_int_op(st.st_size, ==, data_str_len);
+  test_mem_op(data_str, ==, str, data_str_len);
+  tor_free(str);
+  close(fd);
+
+  // assert that the tempfile is removed (should not leave artifacts)
+  str = read_file_to_str(tempname, RFTS_BIN|RFTS_IGNORE_MISSING, &st);
+  tt_assert(str == NULL);
+
+  // Remove old testfile for second test
+  r = unlink(fname);
+  tt_int_op(r, ==, 0);
+  tor_free(fname);
+  tor_free(tempname);
+
+  /*
+  *  Check if it skips using a tempfile with flags
+  */
+  fname = tor_strdup(get_fname("write_chunks_with_no_tempfile"));
+  tor_asprintf(&tempname, "%s.tmp", fname);
+
+  // write a known string to a file where the tempfile will be
+  r = write_bytes_to_file(tempname, temp_str, temp_str_len, 1);
+  tt_int_op(r, ==, 0);
+
+  // call write_chunks_to_file with no_tempfile = true
+  r = write_chunks_to_file(fname, chunks, 1, 1);
+  tt_int_op(r, ==, 0);
+
+  // assert the file has been written (expected size)
+  str = read_file_to_str(fname, RFTS_BIN, &st);
+  tt_assert(str != NULL);
+  tt_int_op(st.st_size, ==, data_str_len);
+  test_mem_op(data_str, ==, str, data_str_len);
+  tor_free(str);
+  close(fd);
+
+  // assert the tempfile still contains the known string
+  str = read_file_to_str(tempname, RFTS_BIN, &st);
+  tt_assert(str != NULL);
+  tt_int_op(st.st_size, ==, temp_str_len);
+  test_mem_op(temp_str, ==, str, temp_str_len);
+
+ done:
+  unlink(fname);
+  unlink(tempname);
+  smartlist_free(chunks);
+  tor_free(fname);
+  tor_free(tempname);
+  tor_free(str);
+  tor_free(data_str);
+  tor_free(temp_str);
+  if (fd >= 0)
+    close(fd);
+}
+
 static void
 test_util_time(void)
 {
@@ -3503,6 +3609,7 @@ struct testcase_t util_tests[] = {
   UTIL_TEST(read_file_eof_tiny_limit, 0),
   UTIL_TEST(read_file_eof_two_loops, 0),
   UTIL_TEST(read_file_eof_zero_bytes, 0),
+  UTIL_TEST(write_chunks_to_file, 0),
   UTIL_TEST(mathlog, 0),
   UTIL_TEST(weak_random, 0),
   UTIL_TEST(socket, TT_FORK),