2.4.4 ICMPv6 Firewall Rules?

[beremonavabi]

Neighbor Advertisement
Neighbor Solicitation
Redirect
Router Advertisement
Router Solicitation

As far as I can see, all of those are solely of use on the local network (one, single segment -- which is all I have):

https://www.computernetworkingnotes.com/networking-tutorials/ipv6-neighbor-discovery-protocol-explained.html

AFAIK, they're used on the WAN link only if I have other subnets that communicate through that interface,
I don't. To me, the outside of the WAN interface is just the internet. And, nothing on the internet should legitimately be sending those to enter my WAN link (again, that I know of). And, as you've said, if something did, it should be discarded by pfSense as it entered. Nothing of mine is on anything but the LAN. AFAIK, the only adjacent devices I care about are internal to the LAN and will happily send those ICMP packets across the LAN without interference. Why would I want to add rules to my WAN's firewall so those packets can come in when I could more easily just leave them off and, with no effort on my part, ensure they never get in regardless of whether or not pfSense should drop them anyway because of the 255 hop limit?

Can you give me a concrete example of how my not allowing those ICMP subtypes into my WAN interface from the internet is breaking anything? That's a real question. I honestly can't think of anything on the internet that would need "a set of messages and processes defined in RFC 4861 that determine relationships between neighboring nodes" (from that link, above) on my local network. But, I'm not an expert.

[beremonavabi]

@jknott

Perhaps we're focusing on different elements. I'm focusing on what's allowed into the LAN. Are you worried about what's happening at the pfSense level? Here are my current rules:

WAN:

I can't see why any of those Neighbor Discover subtypes should be allowed into LAN net (the first rule). But, are you saying they need to be allowed into the WAN address (the second rule)? By blocking them there, am I preventing pfSense from finding external neighbors and routes?

[johnpoz]

You can put the rules there all you want - the hidden rules are hidden ;) And are going to happen before you..

How exactly is your firewall going to talk to the internet via IPv6 on the wan if you do not allow those - so its gateway can be found.. Um you do not need to allow anything other then echo through to your lan from the internet.. etc..

[JKnott]

@beremonavabi said in 2.4.4 ICMPv6 Firewall Rules?:

As far as I can see, all of those are solely of use on the local network (one, single segment -- which is all I have):

I just ran Packet Capture on my WAN interface and saw NS & NA messages. They are there because they are needed. As Johnpoz says, you can't block them anyway. So, what exactly is it you're trying to do? IPv6 relies much more on ICMP than IPv4 and quite frankly won't work without it. Perhaps you need to learn a bit more about IPv6. I can recommend O'Reilly's IPv6 Essentials.

[johnpoz]

Just at a loss to understanding what he is attempting to do..

The required icmpv6 stuff for ipv6 to work on wan - is there!!! Same goes for lan side for clients to find pfsense as their ipv6 gateway.. There is NOTHING you need to add..

All other to wan would be blocked out of the gate - if you want to allow actual ping response.. Then you can add that.. Same sort of thing goes if you want to allow into your lan from outside..

Example I allow echoreq into my my ntp server IPv6 address from internet.. And to ping pfsense IPv6 wan side IP, etc. There is little reason to add any other rules..

[beremonavabi]

According to:

https://www.netgate.com/docs/pfsense/book/network/ipv6-subnets.html?highlight=icmpv6#neighbor-discovery

"...pfSense automatically adds firewall rules on IPv6 enabled interfaces that permit NDP to function. "

Am I supposed to be able to see that rule in my Firewall rules (I don't)? Or is it just an implied rule like the default deny on incoming traffic? Does that statement imply we don't need to add any special ICMPv6 rule at all?

[sigi]

@beremonavabi Maybe you should go once to cli or "Diagnostics / Command Prompt" and execute
"pfctl -s rules" this will help you understand about hidden rules..

[johnpoz]

@beremonavabi said in 2.4.4 ICMPv6 Firewall Rules?:

"...pfSense automatically adds firewall rules on IPv6 enabled interfaces that permit NDP to function. "

You have ZERO add which is what have been telling you ;)

[beremonavabi]

@sigi said in 2.4.4 ICMPv6 Firewall Rules?:

@beremonavabi Maybe you should go once to cli or "Diagnostics / Command Prompt" and execute
"pfctl -s rules" this will help you understand about hidden rules..

Thanks. According to that:

Shell Output - pfctl -s rules
...
pass quick inet6 proto ipv6-icmp all icmp6-type unreach keep state
pass quick inet6 proto ipv6-icmp all icmp6-type toobig keep state
pass quick inet6 proto ipv6-icmp all icmp6-type neighbrsol keep state
pass quick inet6 proto ipv6-icmp all icmp6-type neighbradv keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type echorep keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type routersol keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type routeradv keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type neighbrsol keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type neighbradv keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type echorep keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type routersol keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type routeradv keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type neighbrsol keep state
pass out quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type neighbradv keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type echoreq keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type routersol keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type routeradv keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type neighbrsol keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type neighbradv keep state
pass in quick inet6 proto ipv6-icmp from ff02::/16 to fe80::/10 icmp6-type echoreq keep state
pass in quick inet6 proto ipv6-icmp from ff02::/16 to fe80::/10 icmp6-type routersol keep state
pass in quick inet6 proto ipv6-icmp from ff02::/16 to fe80::/10 icmp6-type routeradv keep state
pass in quick inet6 proto ipv6-icmp from ff02::/16 to fe80::/10 icmp6-type neighbrsol keep state
pass in quick inet6 proto ipv6-icmp from ff02::/16 to fe80::/10 icmp6-type neighbradv keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type echoreq keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type routersol keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type routeradv keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type neighbrsol keep state
pass in quick inet6 proto ipv6-icmp from fe80::/10 to ff02::/16 icmp6-type neighbradv keep state
pass in quick inet6 proto ipv6-icmp from :: to ff02::/16 icmp6-type echoreq keep state
pass in quick inet6 proto ipv6-icmp from :: to ff02::/16 icmp6-type routersol keep state
pass in quick inet6 proto ipv6-icmp from :: to ff02::/16 icmp6-type routeradv keep state
pass in quick inet6 proto ipv6-icmp from :: to ff02::/16 icmp6-type neighbrsol keep state
pass in quick inet6 proto ipv6-icmp from :: to ff02::/16 icmp6-type neighbradv keep state
...

That makes much of this discussion moot. It looks like fSense defaults to allowing (with various restrictions):

Packet Too Big
Destination Unreachable
Echo Reply
Echo Request
Neighbor Advertisement
Neighbor Solicitation
Router Advertisement
Router Solicitation

Oddly, of the Neighbor Discovery subset, it doesn't default to allowing Redirect. I wonder why? Of course, if it defaults to allowing those ICMPv6 subtypes into the system, why not those other "must pass" subtypes:

Parameter Problem (invalid IP header)
Time Exceeded?

[lohphat]

@johnpoz Sorry for bumping this but is there a way to see "hidden" rules? The ICMPv6 "hidden" doesn't seem to allow echo reply so when it's said that pfSense has automatic rules for things to work, but things like echo doesn't work. This ambiguity is a source of some frustration.

[johnpoz]

@lohphat said in 2.4.4 ICMPv6 Firewall Rules?:

there a way to see "hidden" rules?

https://docs.netgate.com/pfsense/en/latest/firewall/viewing-the-full-pf-ruleset.html

[2.4.5-RELEASE][admin@sg4860.local.lan]/root: pfctl -sr | grep ipv6
pass quick inet6 proto ipv6-icmp all icmp6-type unreach keep state
pass quick inet6 proto ipv6-icmp all icmp6-type toobig keep state
pass quick inet6 proto ipv6-icmp all icmp6-type neighbrsol keep state
pass quick inet6 proto ipv6-icmp all icmp6-type neighbradv keep state

Echo reply is not a requirement for ipv6 to function. Other than at the link-local layer its not allowed automatic

pass out quick inet6 proto ipv6-icmp from fe80::/10 to fe80::/10 icmp6-type echorep keep state

There are many more, just touching on the highlights..

Out of the box it doesn't allow ping to wan on ipv4 either, etc.

[lohphat]

@johnpoz Thank you! Just what I was looking for.

When it comes to troubleshooting, knowing the actual rules vs implied is important.

There are gray areas when it comes to implied functionality which could be handled better. e.g. if IPv6 is enabled then due to the inherent need to support multicast groups (e.g. in lieu of ARP) it's not obvious how much of multicast functionality is implied. Is all FE80::/10 traffic allowed? Is IGMPv6 automatically implied (or needed), etc.

It would be nice to have an intro section covering just what is actually in play when VPN, IPv6, et al are enabled for each.

[lohphat]

@johnpoz Here's an interesting find implying that pfSense still isn't multicast complete for either IPv4 or IPv6, in this case not supporting multicast membership management protocols.

https://redmine.pfsense.org/issues/6228

[johnpoz]

The way I read that since set to OS, is that freebsd doesn't support it as of yet. So not really a "pfsense" thing that could be fixed.

[lohphat]

@johnpoz Agreed. I'm a bit surprised as FreeBSD is the basis for router code.

But it does expose the lack of clarity of what functionality is or is not available. If a product claims to support IPv6 but is missing part of the protocol suite that needs to be documented somewhere instead of needing to hunt it down across several domains of dependency (OS, pfSense, OEM, etc.). Having a section listing known limitations, e.g. incomplete protocol suite/RFC implementation would REALLY help.

[johnpoz]

I think your confused about multicast.. Routers don't need to do shit with that.. multicast is suppose to be on the L2...

Membership management for multicast is not really something a router has to do or support.. Do that on your switch! ;) Ie your L2 device..

[lohphat]

@johnpoz Not with IPTV. The multicast streams must pass the firewall. Also, if you have multicast inside the firewall they need to traverse VLANS. Where are the VLANS terminated? pfSense.

Routers, and thus the reason IGMP proxy exists as a package, must be coordinated by all devices, especially routers, not just switches, when different segments must be traversed.

[johnpoz]

That is why IPTV providers gives you their own shit ;)

[lohphat]

@johnpoz Well even without IPTV, I've led multicast video deployments on internal enterprise networks, and as stated, traffic must traverse vlans and routers too. pfSense is a critical router if VLANS are terminated there.

IPv4 made us complacent about multicast, it was easy to ignore, but with IPv6 it's an integral part of the protocol stack and piecemeal protocol stack implementations are not helping. We need to up our game.

All I'm asking is for a call-out in the docs of where the known holes are instead of having to find them on our own.

/end rant ;-)

[JKnott]

@johnpoz said in 2.4.4 ICMPv6 Firewall Rules?:

multicast is suppose to be on the L2...

Multicast can pass through routers, but that must be arranged for. That is normally done with IGMP on IPv4 or MLD on IPv6.