Re: TCP simultaneous (SYN) open with XP Prof SP2

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No, and I haven't done the tests myself. Your post only means
we'll have to redo them soon again as it was interns doing the
testing both times...

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Nat Cracker" <NatCracker@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:51B01BB2-13E3-467E-89A5-68F14E725EDC@xxxxxxxxxxxxxxxx
Hi Alexander,

I installed all the updates (patches) that I could find in Windows Update
this morning. But it did not change the behavior - still sending RST after
SYN-ACK is received.

Do you know which WinXP patch is related to the problem?

Thanks,


"Alexander Nickolov" wrote:

I remember seeing the same behavior two years ago. This year
we redid the tests and the behavior was normal, e.g. working
in this scenario. Note we are using both a connecting and listening
sockets bound to the same local IP address and port. My only
conclusion is that Mictrosoft has quietly fixed this in the last two
years, and perhaps slipped it in a security update. I suggest you
install all WinXP patches and retest.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Nat Cracker" <NatCracker@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:42208141-B010-4D93-8933-06F157327E6B@xxxxxxxxxxxxxxxx
I tested 'TCP Simultaneous (SYN) open' with Windows XP Professional
Version 2002 Service Pack 2. After receiving SYN-ACK packet from remote
host, connection process was aborted and by sending RST to the remote
host.

RFC 793 allows both end hosts to simultaneously send SYN packet to each
other. (Causes SYN_SENT to SYN_RECVD transition) I would like to know
if
Windows XP SP2 supports the simultaneous open as RFC 793 suggests.


Here is what's happening: (Wireshark is used to capture packets on the
wire)

There are two hosts, Host-A and Host-B, tries to connect to each other.
Both
create a TCP socket bound to a specific local IP address and port. Each
host
knows the other's IP address and port to which the host will connect.

1. Host-A and Host-B start connecting to each other at the same time by
calling connect(). (SYNs from the both hosts cross over the network.)

2. Host-A and Host B receives SYN from the remote.

3. Host-A and Host-B sends SYN-ACK to the remote. (SYN-ACKs from the
both
hosts also cross over the network.)

4. Host-A receives the SYN-ACK from Host-B, then it sends RST to Host-B
!!!

5. Host-B receives the SYN-ACK followed by RST from Host-A, then sends
RST
to Host-A.

I have tested with Linux with the same (well of course not exactly)
code
which successfully established the connection.

I am using Visual Studio .NET 2003, and the TCP test client is written
in
C++
using winsock2.

Thanks,






.

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