On Jun 25, 2007, at 10:46 AM, John-Mark Gurney wrote:
It's not the correct behaviour if the only packet coming back is
an Ack of
the FIN (and a FIN) because in the real world, making IE7 throw an
error
screen is not an acceptable option. This is the sort of thing
that gets FreeBSD thrown out on favour of "anything else".
Believe me, our customers are "NOT HAPPY" about this.
Instead of getting an "authorization required" page along with
the opportunity to log in, they get an error, and no opportunity
to log in, which makes the system unusable.
Yes, Blame Microsoft, but we are breaking the TCP spec, not them.
We need to fix this some how.
As bde mention, the bug is in the application... Even SUSv2 says:
When all file descriptors associated with a pipe or FIFO special
file are closed, any data remaining in the pipe or FIFO will be
discarded.
A TCP socket isn't the same thing as a named pape or FIFO. SUSv2
isn't the most relevant standard; RFC-793 is...
Our own close(2) says:
on the last
close of a socket(2) associated naming information and queued
data are
discarded
So, failure of the application to ensure that all data is sent is the
application's fault... bde alluded to a simple work around of
clearing
the non-blocking flag which will return close to the "expected" (but
apprently broken) behavior of keeping the tcp socket around till all
remaining data has been sent...
I must note that the code you quoted has been in FreeBSD since 2.0.
...and the relevant part is section 3.5 (circa pg 37) and the TCP
state diagram on pg 23. Using non-blocking I/O does not mean one can
suddenly shortcut the FINWAIT-1 and FINWAIT-2 states before going
into TIME_WAIT, nor the 2 * MSL timeout before the TCP control block
is allowed to go away.
Otherwise, you might end up sending a RST to a dup'ed packet like a
stray ACK, which seems to be almost exactly the problem at hand.
--
-Chuck
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