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

[Henri Doreau <henri.doreau () gmail com>]

(forgot to CC the list, resending).

2012/8/2 Michal Hlavinka <mhlavink () redhat com>:
> Hi,
>
> we found a bug in ncat (tested with both 6.00 and svn snapshot).
> When file is redirected as input for ncat, it fails with:
>
> > Unable to register IOD #2: Operation not permitted
>
> This error comes from nsock:engine_epoll.c:epoll_iod_register( ):
>
> if (epoll_ctl(einfo->epfd, EPOLL_CTL_ADD, sd, &epev) < 0)
>   fatal("Unable to register IOD #%lu: %s", iod->id, strerror(errno));
>
> The reason is epoll_ctl returns error - EPERM, strace:
> ...
> epoll_ctl(3, EPOLL_CTL_MOD, 4, {...})   = 0
> epoll_ctl(3, EPOLL_CTL_MOD, 4, {...})   = 0
> epoll_ctl(3, EPOLL_CTL_ADD, 0, {...})   = -1 EPERM (Operation not permitted)
> write(2, "Unable to register IOD #2: Opera"..., 50) = 50
> write(2, "\n", 1)                       = 1
> exit_group(1)                           = ?
>
> The reason for this is that fd 0 is regular file and epoll
> is not supported on regular files. man epoll_ctl(2):
>
> ERRORS
> ...
>    EPERM  The target file fd does not support epoll.
>
> Reproducer:
> $ ncat -l 1234 &
> $ touch /tmp/foo
> $ ncat localhost 1234 < /tmp/foo
> Unable to register IOD #2: Operation not permitted
>
> Let me know if you need more information.
>
> Cheers,
> Michal

Hello,

thanks for the detailed bug report. According to [1] there's no
trivial solution to address this issue but I'll work on a fix. The
--nsock-engine=select option can be used as a workaround meanwhile.

Regards.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=15272

-- 
Henri
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