Date: Tue, 21 Jun 2005 08:21:53 GMT From: Pieter de Boer <pieter@os3.nl> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/82470: FreeBSD advertises wrong window scale in some situations Message-ID: <200506210821.j5L8Lrdx014982@www.freebsd.org> Resent-Message-ID: <200506210830.j5L8UIVE015996@freefall.freebsd.org>
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>Number: 82470
>Category: kern
>Synopsis: FreeBSD advertises wrong window scale in some situations
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Jun 21 08:30:18 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator: Pieter de Boer
>Release: 5.4-RELEASE
>Organization:
SNB@UvA
>Environment:
FreeBSD client.wind.surfnet.nl 5.4-RELEASE FreeBSD 5.4-RELEASE #0: Thu Jun 16 17:09:33 CEST 2005 root@:/usr/obj/usr/src/sys/SMP i386
>Description:
Setting a recv buffer of (65535*2)+1 lets FreeBSD advertise a window of 65535<<2 (window scale 2, 256KB) in stead of 65535<<1 (window scale 1, 128KB). So FreeBSD is advertising a window bigger than the actual available receive space. When setting the buffer to 65535*2 exactly, the window scale option is set correctly.
>How-To-Repeat:
sysctl net.inet.tcp.recvspace=131071
Then set up a connection from the FreeBSD system to something else. FreeBSD will advertise a windowsize of 256KB, although there's only 1 byte more than 128KB available.
>Fix:
Haven't had time to look into it yet, sorry.
>Release-Note:
>Audit-Trail:
>Unformatted:
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