This is the mail archive of the cygwin-patches mailing list for the Cygwin project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

RE: Open sockets non-overlapped?

On 19 May 2006 16:20, Lev Bishop wrote:

> Here's a trivial little patch for your consideration (while I wait for
> my copyright assignment to go through).
> It makes it so that cygwin sockets can be passed usefully to windows
> processes. Eg:
> $ cmd /c dir > /dev/tcp/localhost/5001
> However, it's not perfect -- if the windows process just exits, then
> the connection is reset, not shut down gracefully.  

  Well, if the windows process just exits, that is exactly what it has done.
A socket should be shut down gracefully if the app calls shutdown(), and if it
just calls close() the socket should be reset.  That's what "gracefully"

> Playing with
> SO_LINGER doesn't seem to help here. Only way I can think of to make
> it work would be to have the cygwin stub that waits for windows
> processes to exit, to keep a handle on the socket, poll for when the
> windows process closes the socket (using NtQuerySystemInformation
> SystemHandleInformation?) and when it does, close down the socket
> gracefully.

  It probably shouldn't be made to "work" because that would be altering the
semantics of sockets. 
> Anyway, this adds new functionality and doesn't seem to break anything
> that worked before.

  What, you've tested /everything/ that worked before?  ;)
"If you create a socket using the Winsock 2 WSASocket API and you need to
apply a timeout in receive or send operations on the socket, you must
specify the WSA_FLAG_OVERLAPPED flag in the WSASocket call."

>From the MSDN website article;en-us;181610.

  Are we /sure/ cygwin doesn't *depend* on overlapped sockets?  In particular,
can a non-overlapped read be interrupted by a signal?  Have you tested this
vs. both blocking and non-blocking sockets?  This seems to me to be a highly
risky change; I'd like to know what testing you've done.

Can't think of a witty .sigline today....

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]