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List:       linux-net
Subject:    TCP_CLOSE_WAIT: Whose bug is this?
From:       Jamal Hadi <hadi () cyberus ! ca>
Date:       1998-03-29 4:54:30
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This is definetly a bug and it appears to be the remote end.

Here is an infinite loop of packets (infinite because they are there
for hours if not days). 

mypc is a linux box (2.0.*) the remote end is running NEWS-OS6.1.*


---- begin loop ----
11:05:06.217066 inetfw.sonycsl.co.jp.ftp > mypc.1155: F 0:0(0)
ack 1 win 52560 (DF) [tos 0x10]
11:05:06.217066 mypc.1155 > inetfw.sonycsl.co.jp.ftp: . ack 1
win 31744
11:05:06.717066 inetfw.sonycsl.co.jp.ftp > mypc.1155: . ack 1
win 52560 (DF) [tos 0x10]
                                                                       
---- end loop----------

===================
[root@mypc /root]# netstat -t
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address  Foreign Address         State

tcp   57      0     mypc:1155      inetfw.sonycsl.co.j:ftp CLOSE_WAIT

===============

It looks like a bug from NEWS-OS because it keeps sending these
FINs; It looks like a bug from Linux because it keep ACKing 
the FINs in the CLOSE_WAIT state when it should be ignoring
them(according to RFC793 as well as from the quick perusal of the code).
It looks more like a bug from Linux because it never gets out of
the CLOSE_WAIT state; it should after the application closes
(ftp in this case). I wonder when the app is told to close.
It is even more interesting because the receive Q has 57 packets(?)

I think i have seen this behavior before not sure if i can reproduce 
it though. I ftp'ed something using Netscape4.0.* client; the remote
side runs Netscape1.12 server.

I would probably have tried to resolve this but iam extremely
busy at work (totaly non-Linux) so the best i could do is report it.

Any takers? Alan?

cheers
jamal

PS:- I have seen this behavior before, i thing in the CLOSING or
LAST_ACK state; also someone in my Linux user group had reported
it for the LAST_ACK state.
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