Merged revisions 227944 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r227944 | jpeeler | 2009-11-04 17:47:08 -0600 (Wed, 04 Nov 2009) | 14 lines
  
  Fix incorrect filename comparsion after monitor file change
  
  The logic to detect if a requested file is indeed a different file from the
  current file was incorrect. The main issue being confusion of the use of
  filename_base which was previously set without pathing information and then
  compared to another full path. Robust file comparison logic has been added
  to properly check if two files are the same even if symlinks are used.
  
  (closes issue #15313)
  Reported by: caspy
  Patches: 
        20091103__issue15313__1.4.diff.txt uploaded by jpeeler (license 325)
        but mostly tilghman's work
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@227945 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_monitor.c

@@ -315,7 +315,8 @@ int AST_OPTIONAL_API_NAME(ast_monitor_start)(struct ast_channel *chan, const cha
 						directory ? "" : ast_config_AST_MONITOR_DIR, absolute, fname_base);
 			snprintf(monitor->write_filename, FILENAME_MAX, "%s%s%s-out",
 						directory ? "" : ast_config_AST_MONITOR_DIR, absolute, fname_base);
-			ast_copy_string(monitor->filename_base, fname_base, sizeof(monitor->filename_base));
+			snprintf(monitor->filename_base, FILENAME_MAX, "%s/%s",
+					 ast_config_AST_MONITOR_DIR, fname_base);
 		} else {
 			ast_mutex_lock(&monitorlock);
 			snprintf(monitor->read_filename, FILENAME_MAX, "%s/audio-in-%ld",
@@ -560,12 +561,44 @@ int AST_OPTIONAL_API_NAME(ast_monitor_change_fname)(struct ast_channel *chan, co
 		int directory = strchr(fname_base, '/') ? 1 : 0;
 		const char *absolute = *fname_base == '/' ? "" : "/";
 		char tmpstring[sizeof(chan->monitor->filename_base)] = "";
+		int i, fd[2] = { -1, -1 }, doexit = 0;
 
 		/* before continuing, see if we're trying to rename the file to itself... */
 		snprintf(tmpstring, sizeof(tmpstring), "%s%s%s", directory ? "" : ast_config_AST_MONITOR_DIR, absolute, fname_base);
-		if (!strcmp(tmpstring, chan->monitor->filename_base)) {
-			if (option_debug > 2)
-				ast_log(LOG_DEBUG, "No need to rename monitor filename to itself\n");
+
+		/*!\note We cannot just compare filenames, due to symlinks, relative
+		 * paths, and other possible filesystem issues.  We could use
+		 * realpath(3), but its use is discouraged.  However, if we try to
+		 * create the same file from two different paths, the second will
+		 * fail, and so we have our notification that the filenames point to
+		 * the same path.
+		 *
+		 * Remember, also, that we're using the basename of the file (i.e.
+		 * the file without the format suffix), so it does not already exist
+		 * and we aren't interfering with the recording itself.
+		 */
+		ast_debug(2, "comparing tmpstring %s to filename_base %s\n", tmpstring, chan->monitor->filename_base);
+		
+		if ((fd[0] = open(tmpstring, O_CREAT | O_WRONLY, 0644)) < 0 ||
+			(fd[1] = open(chan->monitor->filename_base, O_CREAT | O_EXCL | O_WRONLY, 0644)) < 0) {
+			if (fd[0] < 0) {
+				ast_log(LOG_ERROR, "Unable to compare filenames: %s\n", strerror(errno));
+			} else {
+				ast_debug(2, "No need to rename monitor filename to itself\n");
+			}
+			doexit = 1;
+		}
+
+		/* Cleanup temporary files */
+		for (i = 0; i < 2; i++) {
+			if (fd[i] >= 0) {
+				while (close(fd[i]) < 0 && errno == EINTR);
+			}
+		}
+		unlink(tmpstring);
+		unlink(chan->monitor->filename_base);
+
+		if (doexit) {
 			UNLOCK_IF_NEEDED(chan, need_lock);
 			return 0;
 		}