Date: Sat, 30 Nov 2002 11:46:49 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: freebsd-questions@FreeBSD.ORG Subject: Re: disable inet6? Message-ID: <20021130114649.GA11836@happy-idiot-talk.infracaninophi> In-Reply-To: <20021129212359.A357-100000@13507.net> References: <20021129212359.A357-100000@13507.net>
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On Fri, Nov 29, 2002 at 09:29:00PM -0500, alex wrote:
> I have freebsd 4.7 installed... and it was working just great... till it
> decided it (or me) decided to start inet6...
>
> here's my theory...
>
> got a bunch of daemons that hang on boot... and sometimes on use..
> including sendmail and my ftp server... when i send a message in pine.. it
> takes about a minute to actually send... and this started happening when i
> saw that inet6 showed up on the ifconfig...
That sounds like DNS breakage to me. It's certainly the case that the
sendmail MSP spends a lot of effort looking up the loopback address,
which is ::1 for IPv6. (That is probably what's causing the delays in
pine, too). There are other places where IPv6 stuff can cause the
system to wait for a DNS query to time out, several of which are down
to other people not running properly standards compliant software out
there on the 'net.
You can test how well your system can look up IPv6 addresses by:
dig -x ::1 IN PTR
Ideally this will return 'localhost' within a few milliseconds.
Second best is a negative response (ie. no answer to be found) which
will probably take a second or so to resolve. The worst case is that
you get no answer at all until the resolver gives up and times out.
Other than switching IPv6 off entirely, as has been suggested, you
could try a few other measures to fix up various problematic areas:
* Make sure that:
::1 localhost localhost.your.domain.com
appears in /etc/hosts
* Alternatively run named(8) locally as a caching name server ---
that's essentially what the default configuration in
/etc/namedb/named.conf gets you. Be sure to get the latest
version of that file (1.6.2.6 in the RELENG_4 branch) with the
RFC 3152 stuff in it. Remember to alter /etc/resolv.conf so that
your new nameservice cache becomes your first choice server.
* Modify the configuration in your sendmail configuration (both MSP
and MTA flavours) to tell it only to bind to IPv4 addresses. eg:
FEATURE(no_default_msa)dnl ## overridden with DAEMON_OPTIONS below
DAEMON_OPTIONS(`Port=587,Name=MSA,M=E')dnl
DAEMON_OPTIONS(`Name=IPv4,Family=inet')dnl
in /etc/mail/`hostname`.mc, and
FEATURE(`msp', `[127.0.0.1]')dnl
in /etc/mail/freebsd.submit.mc
* Make your ftp server bind to just the IPv4 address by commenting
out the:
ftp stream tcp6 nowait root /usr/libexec/ftpd ftpd -l
line in /etc/inetd.conf --- send inetd a HUP signal to reload
it's configuration:
killall -HUP inetd
You won't need *all* of these measures --- choose whatever is most
suitable...
Cheers,
Matthew
--
Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks
Savill Way
Marlow
Tel: +44 1628 476614 Bucks., SL7 1TH UK
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