Re: BUG: ncat does not work when file is used as input

[Michal Hlavinka <mhlavink () redhat com>]

On 08/04/2012 12:04 AM, Henri Doreau wrote:
> Hi,
>
> I had to make a tough choice: either introduce a cheesy hack into the
> code of ncat or bloat nsock.
>
> As explained in the link I posted earlier[1], epoll(7) can't deal with
> regular files the same way it does with sockets and pipes.
...
> To sum up what I did (maybe someone comes up with a smarter approach):
>    - hook epoll_ctl() when registering/unregistering events for STDIN_FILENO
>    - create an eventfd(), stored in the engine_info structure (hurk!)
>    - Schedule an aio_read() as a replacement for the actual read().
> This is where it started to become way too intrusive.
>
> The second approach I tried (patch attached) is hackish but simple,
> efficient and far less intrusive. If we're on linux (then epoll() is
> expected to be used, but not even necessarily) and stdin is a regular
> file, then we enforce the use of the select(2)-based nsock engine.

Thank you for the patch, I tested it and it did fix the issue.

I asked a few people about epoll & regular files and I was told, that 
epoll does not work with regular files not because some feature is 
missing, but because it won't make sense there. Correct approach when 
epoll returns EPERM should be to treat it as always ready to write and 
ready to read until EOF is reached. At least that's what I've been told.

Michal

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