Date: Mon, 3 May 2021 09:43:21 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: Doug Hardie <bc979@lafn.org> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: PF with IPv6 Message-ID: <1440325D-2743-4B04-8C20-D86FBC51A322@gromit.dlib.vt.edu> In-Reply-To: <DB4F0B73-57B0-4189-836A-318966FA03A7@sermon-archive.info> References: <mailman.73.1619870406.98508.freebsd-questions@freebsd.org> <90DCF979-C3AE-4775-BE39-DB3F455F7D4E@gromit.dlib.vt.edu> <DB4F0B73-57B0-4189-836A-318966FA03A7@sermon-archive.info>
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On May 2, 2021, at 8:40 PM, Doug Hardie <bc979@lafn.org> wrote: > On 1 May 2021, at 07:37, Paul Mather <paul@gromit.dlib.vt.edu = <mailto: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. >=20 > 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. The "ipv6" protocol in /etc/protocols (protocol 41) is an IPv6 = transition protocol more commonly known as "6in4". It is used by sites = that have only IPv4 connectivity to tunnel IPv6 traffic using IPv4 = packets. The Hurricane Electric TunnelBroker uses 6in4 via protocol 41, = and is a well-known way of getting IPv6 connectivity when your ISP = doesn't provide native IPv6. As you observe, the "ipv6" tunnelling protocol is not the same as the = IPv6 address family (AF_INET6). Glad you got it sorted out and working, though. Cheers, Paul.
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