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Re: IPV6 router works, but clients fail

On Thursday 02 July 2009 22:23:20 Miles Nordin wrote:
> >>>>> "rm" == Roy Marples <> writes:
>     rm> I needed to clamp max-mss in pppoe0 to 1432. It used to be
>     rm> 1452, which I recall was needed for my wireless
>     rm> clients. Probably the extra overhead of IPv6.
> The PPPoE MTU problem should not exist on IPv6, and at my site where I
> have <1500 links to the internet I didn't have to change mss-scrubbing
> smaller for IPv6.  It's possible you are creating the PPPoE problem
> yourself somewhere by blocking ICMPv6 'too-big' packages.

I've attached my current pf.conf
As Brian pointed out in this thread, PF does not handle IPv6 fragments which 
could be the issue as well. However, the router does need a firewall as it's 
also my server.

> You should never find you need the mss scrubbing to reach the Internet
> period---if you do, you must be blocking too much ICMP on your end.
> The symptom of needing smaller mss scrubbing is that a few of other
> people's misconfigured sites on the Internet don't work, just a few
> not all.  I wish you would have a look to your ICMP rules to avoid
> publishing bad examples which will infect other sites and spread the
> PPPoE problem.
> The way it's documented/supposed to work, you must either pass too-big
> / frag-needed ICMP, *or* use 'keep state' TCP rules which pass that
> ICMP implicitly.  The way it actually works, I'm not so sure.

Well the router and clients passes all ICMP packets - the clients didn't even 
have firewalls installed. Anyway, here's the lines from the attached pf.conf
pass in proto icmp all
pass in proto ipv6-icmp all

It doesn't help that I'm using a PPPoA->PPPoE modem, which apparently affects 
things as well.

Interestingly enough, if I drop the MTU on my clients to 1492 then I don't 
need the scrub mss line. Anyone have an opinion on which would be better?


#       $NetBSD: pf.conf,v 1.4 2008/06/18 09:06:25 yamt Exp $
#       $OpenBSD: pf.conf,v 1.34 2007/02/24 19:30:59 millert Exp $
# See pf.conf(5) and /usr/share/examples/pf for syntax and examples.
# Remember to set net.inet.ip.forwarding=1 and/or net.inet6.ip6.forwarding=1
# in /etc/sysctl.conf if packets are to be forwarded between interfaces.

mynets="{ $int_net, $int_inet6 }"

# asterisk needs 5060 (tcp, udp) and 4569 (udp)
# We special case ssh and domain
tcp_services="{ ident, smtp, www, imap, git, svn, \
                ftp, ftp-data, 50000:50100, svn, rsync }"

# options
set block-policy return
set loginterface $ext_if
set skip on lo

# scrub
scrub in
# We need to clamp max-mss so that IPv6 wireless clients work
scrub out on pppoe0 max-mss 1432

# Schedulers
altq on  $ext_if priq bandwidth 500Kb \
        queue { std_out, ssh_out, dns_out, tcp_ack_out  }
queue std_out           priq(default)
queue ssh_out           priority 4 priq(red)
queue dns_out           priority 5
queue tcp_ack_out       priority 6

altq on $int_if cbq bandwidth 3.5Mb \
        queue { std_in, ssh_in, dns_in }
queue std_in            cbq(default)
queue ssh_in            priority 4
queue dns_in            priority 5

# nat/rdr
nat on $ext_if inet from !($ext_if) -> ($ext_if:0)
nat-anchor "ftp-proxy/*"
rdr-anchor "ftp-proxy/*"
rdr pass on $int_if inet proto tcp from any to any port ftp -> port 

rdr-anchor miniupnpd
anchor miniupnpd

# filter rules
block in log all
anchor "ftp-proxy/*"
antispoof quick for lo 
# antispoof fails for inet6?
antispoof quick for { $int_if } inet

pass out
pass from { $int_net, $int_net6 } to any

pass in proto icmp all
pass in proto ipv6-icmp all

pass in proto tcp from any to self port ssh queue ssh_out
pass in proto tcp from any to self port domain queue dns_out
pass in proto tcp from any to self port $tcp_services \
    queue(std_out, tcp_ack_out)

# To allow IPv6 traffic to move unmolested to our LAN
block quick from any to $int_addr6
pass in from any to $int_net6

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