Date: Sun, 2 May 2021 17:40:26 -0700 From: Doug Hardie <bc979@lafn.org> To: Paul Mather <paul@gromit.dlib.vt.edu> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: PF with IPv6 Message-ID: <DB4F0B73-57B0-4189-836A-318966FA03A7@sermon-archive.info> In-Reply-To: <90DCF979-C3AE-4775-BE39-DB3F455F7D4E@gromit.dlib.vt.edu> References: <mailman.73.1619870406.98508.freebsd-questions@freebsd.org> <90DCF979-C3AE-4775-BE39-DB3F455F7D4E@gromit.dlib.vt.edu>
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> On 1 May 2021, at 07:37, Paul Mather <paul@gromit.dlib.vt.edu> wrote: >=20 > On Fri, 30 Apr 2021 21:20:48 -0700, Doug Hardie <bc979@lafn.org = <mailto:bc979@lafn.org>> wrote: >=20 >> Message: 3 >> Date: Fri, 30 Apr 2021 21:20:48 -0700 >> From: Doug Hardie <bc979@lafn.org <mailto:bc979@lafn.org>> >> To: FreeBSD Questions <freebsd-questions@freebsd.org = <mailto:freebsd-questions@freebsd.org>> >> Subject: PF with IPv6 >> Message-ID: <2CD4806C-F1A4-4DDE-8C2F-2B0A08EA2A18@sermon-archive.info = <mailto:2CD4806C-F1A4-4DDE-8C2F-2B0A08EA2A18@sermon-archive.info>> >> Content-Type: text/plain; charset=3Dus-ascii >>=20 >> FreeBSD 13-RELEASE. I have a small test network setup and tried to = block all IPv6 except those addressed to a specific address. = /etc/pf.conf contained: >>=20 >> ext_if =3D "bge0" >> LAN3 =3D "2001:1000:0:3000::/64" >> pass in quick log on $ext_if proto ipv6 from $LAN3 to $LAN3 >> block in log on $ext_if proto ipv6 from any to any >>=20 >> Nothing got blocked. pftop showed all zeros for both rules. I then = added at the end: >>=20 >> pass in quick log on $ext_if proto icmp6 from $LAN3 to $LAN3 >> block in log on $ext_if proto icmp6 from any to any >>=20 >> A lot of stuff got blocked. The log shows many entries like: >>=20 >> 15:59:41.597632 rule 3/0(match): block in on bge0: (hlim 1, = next-header Options (0) payload length: 32) fe80::120c:6bff:fe5d:4404 > = ff02::1: HBH (rtalert: 0x0000) (pad1)(pad1) ICMP6, multicast listener = query >> 0x0000: 6000 0000 0020 0001 fe80 0000 0000 0000 = `............... >> 0x0010: 120c 6bff fe5d 4404 ff02 0000 0000 0000 = ..k..]D......... >> 0x0020: 0000 0000 0000 0001 3a00 0502 0000 0000 = ........:....... >> 0x0030: 8200 98aa .... >>=20 >> Rule 3 is the block for ICMP6, but those are clearly IP6 packets that = should have been blocked by rule 1. Is there a problem with IPv6 and pf? >=20 >=20 > It's not clear to me precisely what you are trying to achieve. The = "proto" keyword in PF rules refers to protocols in /etc/protocols. Your = rules appear to be targeting the specific case of filtering IPv6 = encapsulated in IPv4. I don't believe that is what you intend. >=20 > The more standard way in PF to block IPv6 vs IPv4 traffic is to use = "inet" (IPv4) or "inet6" (IPv6) to target IPv4 or IPv6 packets. >=20 > Note, the last rule you added that you say did start blocking things = is more typical of rules to block ICMP6. Because you omit "inet" or = "inet6" on the rule it will be applied to both IPv4 and IPv6 packets. = But, the "proto icmp6" part is specifically targeting ICMP6. >=20 > So, to summarise, use "inet" and "inet6" to select IPv4 and IPv6 and = "proto" to select the protocol you want to target (e.g., "tcp", "udp", = "icmp", "icmp6", etc.). E.g., "pass in log quick on $ext_if inet6 from = ..." to allow all IPv6 for the rule, or ""pass in log quick on $ext_if = inet6 proto tcp from ..." to allow only IPv6 TCP traffic, etc. First, it appeared to me that since ipv6 is listed in /etc/protocols, = that it could be used as a protocol. However, after reading the man = page again, I see where it wants family, not protocol. With that change = it does work. What I was trying to do was to simulate a multi LAN configuration using = only one physical LAN. This is quite easy to do with IPv4, but even = with a bunch of pf rules, there are issues with the multicast packets. = Hosts should only listen to packets addressed to their virtual LAN but = multicast packets are not identifiable by which virtual LAN they were = sent to. So I ended up adding a bunch of switches and building the = complete multi LAN configuration. Thanks, --Doug
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