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RE: NT SP6 and WouldBlock in HTTCP.C - Seemingly broken

From: Jens Meggers <jens.meggers@firepad.com>
Date: Thu, 3 May 2001 18:09:15 -0700
Message-ID: <DDF913B74F07D411B22500B0D0206D9F4EF117@FIREPLUG>
To: "'Fred Covely'" <fcovely@covely.com>, www-lib@w3.org

during my latest experiments, I finally found a NT 4.0 service pack 4
installation that caused the problem you described. After calling connect()
two times, it returns with an error, but WSAGetLast() error returns 0
altough the connection is already set up.
There is a quite clean workaround for that. We can use the select() command
to check whether there is a connection or not before throwing back an error
code. This can be done right before the "if (socerrno == EISCONN) {"
statement in the TCP_NEED_CONNECT state of HTDoConnect(). I've inserted the
following code:

		// check if socket is connected. If yes, enter next stage
		fd_set writefds;
		struct timeval timeout;
		int select_ret;

		FD_SET(HTChannel_socket(host->channel), &writefds);
		timeout.tv_sec =  0;
		timeout.tv_usec = 0;
		select_ret = select ( 0,  NULL, &writefds,  NULL, &timeout
		if (select_ret == 1) {
		    host->tcpstate = TCP_CONNECTED;
		    HTTRACE(PROT_TRACE, "HTHost %p going to state
TCP_CONNECTED.\n" _ host);

I also attached my HTTCP.c to this mail. Please not that it also continas
the code for checking the event error code. 

What do you think?



-----Original Message-----
From: Fred Covely [mailto:fcovely@covely.com]
Sent: Dienstag, 24. April 2001 17:29
To: Jens Meggers; www-lib@w3.org
Subject: RE: NT SP6 and WouldBlock in HTTCP.C - Seemingly broken

Congratulations, thats the fastest bug fix I ever saw (8>).

I'm real curious as to your solution.

I'm not seeing any issues with this on win2k, only NT.  But the
user I have on NT SP6 fails hard everytime.  I think I'll go
ahead and set up an NT/SP6 box and see if I can reproduce
with and without your patch when it comes out.


Fred Covely

-----Original Message-----
From: Jens Meggers [mailto:jens.meggers@firepad.com]
Sent: Tuesday, April 24, 2001 5:08 PM
To: 'Fred Covely'; www-lib@w3.org
Subject: RE: NT SP6 and WouldBlock in HTTCP.C - Seemingly broken


I solved the problem within the last weeks. I had to pass the error message
that the asyn event messages of the socket call is carrying with the event
object to the HTDoConnect method. Actually, it works. Unfortunatly, a lot of
files are involved. I will send a patch description asap.


-----Original Message-----
From: Fred Covely [mailto:fcovely@covely.com]
Sent: Dienstag, 24. April 2001 17:09
To: www-lib@w3.org
Subject: NT SP6 and WouldBlock in HTTCP.C - Seemingly broken

I have run into an interesting problem on NT SP 6 on at
least one machine.  I've done a detailed trace on the box
that is failing and on several Win2K boxes that work.

Clearly based on the source comments there has been a lot
of work done in this area, so I would request your input
on this problem.

Here is the scenario:

We are doing a simple httpget on a public site (yahoo.com, or whatever).
On a win2K machine the sequence in HTTCP.C looks like this:

1224  15:50:44        Event....... Registering socket for HTEvent_CONNECT
1224  15:50:44        HTDoConnect. rcode `10035'
1224  15:50:44        HTDoConnect. status `-1'
1224  15:50:44        HTDoConnect. WOULD BLOCK `www.yahoo.com'
1224  15:50:44      Host Event.. WRITE passed to `http://www.yahoo.com'
1224  15:50:44      HTDoConnect. rcode `10056'
1224  15:50:44      HTDoConnect. status `-1'
1224  15:50:44      HTHost 01099988 going to state TCP_CONNECTED.
1224  15:50:44      Event....... Socket 456 unregistered for HTEvent_CONNECT
1224  15:50:44      DNS weight.. Home 5 has weight 0.00
1224  15:50:44      HTHost 01099988 connected.
1224  15:50:44      Host connect Unlocking Host 01099988
1224  15:50:44      StreamStack. Constructing stream stack for text/x-http
to */*

The Win2K request then proceeds normally.

On the NT SP 6 machine the same request looks like this:

286  14:40:54        Event....... Register socket 248, request 0082B640
286  14:40:54        HTDoConnect. rcode `10035'
286  14:40:54        HTDoConnect. status `-1'
286  14:40:54        HTDoConnect. WOULD BLOCK `www.yahoo.com'
286  14:41:39      Host Event.. WRITE passed to `http://www.yahoo.com'
286  14:41:39      HTDoConnect. rcode `10035'
286  14:41:39      HTDoConnect. status `-1'
286  14:41:39      HTDoConnect. WOULD BLOCK `www.yahoo.com'
286  14:42:24      Host Event.. WRITE passed to `http://www.yahoo.com'
286  14:42:24      HTDoConnect. rcode `10035'
286  14:42:24      HTDoConnect. status `-1'
286  14:42:24      HTDoConnect. WOULD BLOCK `www.yahoo.com'
286  14:43:09      Host Event.. WRITE passed to `http://www.yahoo.com'
286  14:43:09      HTDoConnect. rcode `10035'
286  14:43:09      HTDoConnect. status `-1'

In inspecting the Microsoft web site on the connect, they clearly
state that the preferred implementation is not to use multiple
connect calls.  I don't have enough familiarity with the libwww
code to venture a guess as to what is wrong.  Could it be related
to the multiple connect strategy?  If so has anyone looked at
the best way to do this?  I see a comment of about a year ago
from jens@meggers.com indicating there were known ms problems
in this area.  I have a hard time believing someone has not
figured out how to do an absolutely bullet proof connect in windows.

Any input greatly appreciated.

Fred Covely

Received on Thursday, 3 May 2001 21:21:06 UTC

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