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List:       squid-dev
Subject:    Re: concurrent requests?
From:       Henrik Nordstrom <hno () hem ! passagen ! se>
Date:       2000-05-31 21:32:07
Message-ID: 393584D7.12749BE0 () hem ! passagen ! se
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Adrian Chadd wrote:

> I drew some of this out on paper after I sent my last mail. To detect
> half-closed connections you read the FD and if EOF under certain
> conditions you want. You can't poll the fd since the FD will always
> return read ready. .. so yu need to do a read() and handle the
> return. What I was thinking about is to 'inject' data into a comm_read().
> That would be a neat solution. Got any other suggestions ?

You only need to detect this once. Then it is a known fact. You cannot
receive any more from that socket.

My suggesting is to simply have comm_read return EOF and then be done
with it. After that no further comm_read should be issued on that
filedescriptor, and should return EOF if attempted. comm_read should
never mark a EOF state filedescriptor for select.

For a binady data stream EOF is usually indicated by zero bytes of data
returned.

write will tell you if there are any error sending data out on the
socket, and getsockopt(..SO_ERROR) can be used to periodically poll the
socket for errors when there is no activity. Polling for an error only
useful if keep-alives are enabled or the client properly sends RESET
when aborting the connection (ABORT TCP operation, defined in Internet
Standard 6 but not covered in the "standard" sockets API).

/Henrik

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Subject: Re: concurrent requests?
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To: Adrian Chadd <adrian@creative.net.au>
From: Henrik Nordstrom <hno@hem.passagen.se>
Sender: hno@hem.passagen.se
Cc: squid-dev@squid-cche.org

Adrian Chadd wrote:

> I drew some of this out on paper after I sent my last mail. To detect
> half-closed connections you read the FD and if EOF under certain
> conditions you want. You can't poll the fd since the FD will always
> return read ready. .. so yu need to do a read() and handle the
> return. What I was thinking about is to 'inject' data into a comm_read().
> That would be a neat solution. Got any other suggestions ?

You only need to detect this once. Then it is a known fact. You cannot
receive any more from that socket.

My suggesting is to simply have comm_read return EOF and then be done
with it. After that no further comm_read should be issued on that
filedescriptor, and should return EOF if attempted. comm_read should
never mark a EOF state filedescriptor for select.

For a binady data stream EOF is usually indicated by zero bytes of data
returned.

write will tell you if there are any error sending data out on the
socket, and getsockopt(..SO_ERROR) can be used to periodically poll the
socket for errors when there is no activity. Polling for an error only
useful if keep-alives are enabled or the client properly sends RESET
when aborting the connection (ABORT TCP operation, defined in Internet
Standard 6 but not covered in the "standard" sockets API).

/Henrik



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