On Jun 6, 2015 4:56 PM, "Anil Madhavapeddy" <anil@xxxxxxxxxx> wrote:
>
> I'm just testing out tuntap.1.3 for release on Linux, and am having some trouble getting it to work. Just wanted to check if others are using it ok. I've done:
>
> $ sudo tunctl
> $ sudo ifconfig tap0 10.0.0.1 netmask 255.255.255.0 up
> $ sudo ./_build/test/nonblock_read.native tap0
> read: 0
> read: 0
> ...
>
> This results in a stream of 0 byte reads.
>
> If I change the Lwt_unix.of_unix_file_descr in mirage-net-unix to be blocking:true instead of blocking:false, then it works as expected on Linux, and all the tap networking is ok. Tracing through the Lwt code shows that blocking:false should work, but for some reason the tap device on Linux is always readable and so EWOULDBLOCK never happens.
>
> Anyone else having this problem on Linux, or is it just me? I don't often use tap networking there, so I don't want to apply the above workaround without understanding it.
I had what sounds like the same problem with tap devices and rump kernel.
I haven't yet filed a bug but I think there is one... 0 length reads should not happen. I am not sure if it changed in recent versions but I think it may have. Planning to investigate. If you do the first open with nonblock it seems to work but fcntl does not
