Date: Sat, 18 Nov 1995 21:59:16 +0300 From: Andrew Timonin <tim@Relcom.EU.net> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it>, Ollivier Robert <roberto@keltia.freenix.fr> Cc: davidg@Root.COM, hackers@freebsd.org Subject: Re: TIME_WAIT and linear chain of TCPCBs (was: ...beat a WEB server to death) Message-ID: <WB4qYhmKRz@sssun.spb.su> In-Reply-To: <199511132341.AAA04886@keltia.freenix.fr>; from Ollivier Robert at Tue, 14 Nov 1995 00:41:57 %2B0100 (MET) References: <199511132341.AAA04886@keltia.freenix.fr>
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In message <199511132341.AAA04886@keltia.freenix.fr> Ollivier Robert
writes:
>It seems that Luigi Rizzo said:
>>
>> especially because they do not derive from a bug but from a feature :)
>
>There was talk about something somewhat related in bugtraq about half
>opened connections (SYN_RECV then nothing else) and the possible denial of
>service...
I still have no time to look in 2.1 sources, but in 2.0.5 there was
a bug in ip_icmp.c in ICMP_UNREACH type processing.
It look like a misprint, you may see it from a diff:
*** ip_icmp.c.orig Tue May 30 12:09:42 1995
--- ip_icmp.c Sat Oct 21 13:01:50 1995
***************
*** 240,246 ****
case ICMP_UNREACH_PROTOCOL:
case ICMP_UNREACH_PORT:
case ICMP_UNREACH_SRCFAIL:
! code += PRC_UNREACH_NET;
break;
case ICMP_UNREACH_NEEDFRAG:
--- 240,246 ----
case ICMP_UNREACH_PROTOCOL:
case ICMP_UNREACH_PORT:
case ICMP_UNREACH_SRCFAIL:
! code = PRC_UNREACH_NET;
break;
case ICMP_UNREACH_NEEDFRAG:
----------------
This may lead to a large number of TCP connections in SYN RECEIVED state,
for ex. on large mail relays when some site without a back route to it is
trying to semd mail to this relay. It sends SYN, which reach relay via
for ex. default route. Relay sends SYN back, but get ICMP_UNREACH as
a reply :-(. But because of this misprint tcp socket will not be closed
as it should be, but will hang waiting for timeout expire.
> --
>Ollivier ROBERT -=- The daemon is FREE! -=- roberto@keltia.frmug.fr.net
> FreeBSD keltia.freenix.fr 2.2-CURRENT #1: Sun Nov 12 16:47:05 MET 1995
--
Andrew A. Timonin E-mail tim@sssun.spb.su,
St.Petersburg phone: office: +7 (812) 1106762
Russia private: +7 (812) 2540779
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