--- a/src/core/ngx_connection.h
+++ b/src/core/ngx_connection.h
@@ -79,4 +79,19 @@ EV_VNODE        should notify by some si
                 or stat if aged >= N seconds (big enough)
 #endif
 
+
+extern ngx_chain_t *(*ngx_write_chain_proc)
+                                        (ngx_connection_t *c, ngx_chain_t *in);
+
+
+ngx_chain_t *ngx_write_chain(ngx_connection_t *c, ngx_chain_t *in, off_t flush);
+
+
+/* TODO: move it to OS specific file */
+#if (__FreeBSD__)
+ngx_chain_t *ngx_freebsd_write_chain(ngx_connection_t *c, ngx_chain_t *in);
+ngx_chain_t *ngx_aio_write_chain(ngx_connection_t *c, ngx_chain_t *in);
+#endif
+
+
 #endif /* _NGX_CONNECTION_H_INCLUDED_ */