utils: Add convenience function for setting fd flags

There are many places in the code base where we ignore the return value
of fcntl() when getting/setting file descriptior flags. This patch
introduces a convenience function that allows setting or clearing file
descriptor flags and will also log an error on failure for later
analysis.

Change-Id: I8b81901e1b1bd537ca632567cdb408931c6eded7

main/utils.c

@@ -2749,3 +2749,37 @@ int ast_compare_versions(const char *version1, const char *version2)
 	}
 	return extra[0] - extra[1];
 }
+
+int __ast_fd_set_flags(int fd, int flags, enum ast_fd_flag_operation op,
+	const char *file, int lineno, const char *function)
+{
+	int f;
+
+	f = fcntl(fd, F_GETFL);
+	if (f == -1) {
+		ast_log(__LOG_ERROR, file, lineno, function,
+			"Failed to get fcntl() flags for file descriptor: %s\n", strerror(errno));
+		return -1;
+	}
+
+	switch (op) {
+	case AST_FD_FLAG_SET:
+		f |= flags;
+		break;
+	case AST_FD_FLAG_CLEAR:
+		f &= ~flags;
+		break;
+	default:
+		ast_assert(0);
+		break;
+	}
+
+	f = fcntl(fd, F_SETFL, f);
+	if (f == -1) {
+		ast_log(__LOG_ERROR, file, lineno, function,
+			"Failed to set fcntl() flags for file descriptor: %s\n", strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}