Date: Wed, 19 Mar 1997 11:37:32 +0100 From: Luigi Rizzo <luigi@iet.unipi.it> To: FreeBSD-gnats-submit@freebsd.org Subject: kern/3036: No initial slow start Message-ID: <199703191037.LAA05550@prova.iet.unipi.it> Resent-Message-ID: <199703191050.CAA16035@freefall.freebsd.org>
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>Number: 3036
>Category: kern
>Synopsis: No initial slow start
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Mar 19 02:50:01 PST 1997
>Last-Modified:
>Originator: Luigi Rizzo
>Organization:
DEIT
>Release: FreeBSD 2.1.7 and 2.2, possibly 3.0 as well
>Environment:
FreeBSD 2.1.X, 2.2.X
>Description:
our implementation of TCP does not do "slow start" at
connection opening on "local" networks. Too bad, because of
the way "SUBNETSARELOCAL" is defined in in.c all addresses on
the same CLASS_A, CLASS_B or CLASS_C network are considered
local irrespective of netmasks.
This bug came in around rev. 1.11 of tcp_input.c when TTCP
support was enabled. Since then TTCP has become non optional
in 1.14
I reported it around september when I first noticed it across
my ppp link, and there was some agreement (from Garret I
believe) that at least workaround #2 below was to become the
default. Unfortunately the patch has probably been forgotten.
>How-To-Repeat:
use TCP between hosts sharing the same upper 16-bit of a
CLASS_B address.
>Fix:
[workaround #1] define SUBNETSARELOCAL=0 in the kernel config file.
[workaround #2] change the default definition of SUBNETSARELOCAL to 0 in
file in.c
[fix] i am not sure at all if the "optimization" indicated above is
acceptable, especially for non-TTCP stuff. At the very least it
should be used only after TTCP has been negotiated.
Luigi
====================================================================
Luigi Rizzo Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it Universita' di Pisa
tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 http://www.iet.unipi.it/~luigi/
====================================================================
>Audit-Trail:
>Unformatted:
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