Re: accept() and setsockopt() and port scans
Re: accept() and setsockopt() and port scans
- Subject: Re: accept() and setsockopt() and port scans
- From: Quinn <email@hidden>
- Date: Thu, 31 Jan 2008 11:05:54 +0000
At 10:53 +1300 31/1/08, Glenn Anderson wrote:
Sometimes when this happens, accept() returns an address_len of 0. I
see this on both Mac OS X 10.4 and 10.5. On Mac OS X 10.5
setsockopt(x, SOL_SOCKET, SO_NOSIGPIPE, ...) also fails with EINVAL
in this case. Depending on the timing of the RST, I have also seen a
correct address_len from accept() but the subsequent setsockopt()
fails.
Is accept() returning an address_len of 0 and setsockopt() failing
with EINVAL intended behavior? If it is intended, is it documented
anywhere? The man pages for these calls definitely don't mention
this behavior.
There are two cases here.
A. accept returns a valid address and setsockopt fails afterwards --
This seems like reasonable behaviour on behalf of the kernel. It
gave you back a valid socket but the socket shut down before you
called setsockopt. The standard specifically states that EINVAL can
be caused by:
The specified option is invalid at the specified socket level
or the socket has been shut down.
<http://www.opengroup.org/onlinepubs/009695399/functions/setsockopt.html>
I suspect that the UNIX '03 conformance changes are the reason why
you're seeing different behaviour on 10.4 vs 10.5.
B. accept returns a null address -- This smells like a bug to me.
Definitely Radar-worthy IMHO.
<http://developer.apple.com/bugreporter/>
Please send me the bug number. Also, if you can include code that
reproduces the problem, that will definitely improve the chances of
it getting fixed (-:
While debugging this, I couldn't help wondering if there any way to
check the state of a socket to see if the connection has shut down,
like OTGetEndpointState under OS 9?
I expect that your best bet is <x-man-page://2/getpeername>. This is
traditionally used by sockets code to test whether a connection is in
place. For example, when doing non-blocking connects, you typically
use getpeername to determine whether the connect succeeded or failed.
S+E
--
Quinn "The Eskimo!" <http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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