Re: [Nmap, Ncat] Odd Nsock bug related to ENETUNREACH

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

2014-06-05 13:38 GMT+02:00 Jacek Wielemborek <d33tah () gmail com>:
> List,
>
> While working on my prototype, I noticed that when you try to
> make a connection that results in ENETUNREACH (tested by issuing
> ncat 127.0.0.0 -w 1), Nsock blocks forever even if a timeout was
> specified. This is probably because it performs a non-blocking
> connect() and ignores any error codes other than EINPROGRESS or
> EAGAIN, yet it schedules an event. Then, the main loop calls
> engine's file descriptor watching function (epoll, select etc) on
> an empty FD set, effectively waiting forever.
>
> This affects NSE scripts as well. Create test.nse file with the
> folowing code and run nmap --script test.nse -d 127.0.0.0 -sn:
>
> local stdnse = require "stdnse"
> local nmap = require "nmap"
>
> hostrule = function()
>   return true
> end
>
> action = function(host)
>         stdnse.print_debug("test.nse started!")
>         local sock = nmap.new_socket()
>         local constatus, conerr = sock:connect("127.0.0.0", 80)
> end
>
> --END OF FILE
>
> I believe that Nsock should run the connect handler immediately
> when it detects the error, behaving in a way similar to other
> error messages.
>
> The box I tested it on is Fedora 20, kernel
> 3.14.2-200.fc20.x86_64. I can provide any further details if
> needed.
>
> Yours,
> Jacek Wielemborek

Interesting... I need to investigate this. I have added a new nsock
regression test. What I could observe is that the error is delivered,
but it breaks afterwards due to bad refcounts or something like this
(according to the engine you use). There's definitely something wrong
there.

I'll have a closer look as soon as time permits.

Regards

-- 
Henri
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