add uv udp try send

Please review the commits and give me comments on them.
2014-07-02 14:33 GMT+02:00 Iñaki Baz Castillo <ibc@aliax.net>:
>> > +  do {
>> > +    size = sendmsg(handle->io_watcher.fd, &h, 0);
>> > +  } while (size == -1 && errno == EINTR);
>> > +
>> > +  if (size == -1) {
>> > +    if (errno == EAGAIN || errno == EWOULDBLOCK)
>> > +      return 0;
>> > +    else
>> > +      return -errno;
>>
>> This has to return -EAGAIN.
>
>
> Why should it return -EAGAIN? If sendmsg() fails due to EMSGSIZE it must
> return -EMSGSIZE (which becomes UV_MSGSIZE). Do I miss something?

Sorry, I wrongly understood that you meant the return value after the else.