joyent/libuv — comment on commit 36903d39168ccec38b523ea40847890c9bbc7a9c
File: src/win/udp.c line 257
By igorzi:

Maybe these should be fields in uv_udp_t? so that we wouldn't have to do the handle->flags & UV_HANDLE_SYNC_BYPASS_IOCP check every time.