Re: [Dorset] Wimborne Model Town Routing Problem
On Monday, 18 April 2022 20:26:36 BST Patrick Wigmore wrote: > I suppose one thing to check is whether, while connected to the VPN, > you have any other (conflicting) routes to 192.168.0.0/24. Or, indeed, > whether there is a route to 192.168.0.0/24 at all. E.g. run > > $ ip route show > > on your VPN client computer and see where it thinks it should send > traffic destined for 192.168.0.0/24. Here it is: terry@OptiPlex:~/Useful$ ip route show default via 192.168.1.1 dev eno1 proto dhcp metric 100 169.254.0.0/16 dev eno1 scope link metric 1000 192.168.1.0/24 dev eno1 proto kernel scope link src 192.168.1.21 metric 100 -- Terry Coles -- Next meeting: Online, Jitsi, Tuesday, 2022-05-03 20:00 Check to whom you are replying Meetings, mailing list, IRC, ... http://dorset.lug.org.uk New thread, don't hijack: mailto:dorset@mailman.lug.org.uk
Re: [Dorset] Wimborne Model Town Routing Problem
On 18/04/2022 20:26, Patrick Wigmore wrote: On Mon, 18 Apr 2022 10:23:19 +0100, Terry Coles wrote: When a VPN client connects to the Web Server, in theory the web server would see that connection coming in from a 10.1.10.0/24 address, not a 192.168.0.0/24 one. So, it is a given that the Webserver has to be configured to accept connections from 10.1.10.0/24 clients. So how would I do that? I always assumed that the VPN Server included a router that would sort all that out. The iptables output would indicate that it does. I suppose there is some nuance here; the connection would come from a 10.1.10.0/24 address, routed via the 192.168.0.0/24 address of the VPN server. So, the Webserver would see that 192.168.0. had forwarded it some traffic that originated from 10.1.10.x. If the VPN server were doing NAT routing/masquerading, as opposed to plain old routing, then the connection would appear to come directly from the VPN server's 192.168.0.0/24 address. I suppose the VPN server *could* be doing NAT routing, but that would be a little surprising to me, because I am not seeing how NAT routing would be beneficial in this set-up. But I only mentioned this in case you had configured the server to block connections that weren't from 192.168.0.0/24 addresses, so if you haven't done that then I can't see it being a concern. The only other thing that comes to mind on a brief reading of your response to me is that, if the web server isn't accessible by IP address, then it certainly isn't going to be accessible via hostname. So, as you say, the routing falls under suspicion. The finer points of iptables configuration are perhaps a bit lost on me, so while I can look at the broad-strokes of your config, and I think it seems OK, I could easily be missing some nuances that might send it off the rails. I suppose one thing to check is whether, while connected to the VPN, you have any other (conflicting) routes to 192.168.0.0/24. Or, indeed, whether there is a route to 192.168.0.0/24 at all. E.g. run $ ip route show on your VPN client computer and see where it thinks it should send traffic destined for 192.168.0.0/24. That raises the question of how the VPN client learns which networks it can route to via the VPN. Presumably it does learn something, since you can access the various non-Webserver devices in the 192.168.0.0/24 network. Unless that's happening by fluke. If there isn't a suitable route to 192.168.0.0/24 on the VPN client computer, then manually adding one temporarily might be a worthwhile experiment. It seems you've got me hooked on this puzzle, Terry. I was only going to write a few paragraphs here, to clarify my previous remarks! Patrick Note: The VPN Server does not do NAT, as is evidenced by the "Last login from 10.1.10.x" prompt that I get after SSHing into one of the pis periodically. Hamish -- Next meeting: Online, Jitsi, Tuesday, 2022-05-03 20:00 Check to whom you are replying Meetings, mailing list, IRC, ... http://dorset.lug.org.uk New thread, don't hijack: mailto:dorset@mailman.lug.org.uk
Re: [Dorset] Wimborne Model Town Routing Problem
On Mon, 18 Apr 2022 10:23:19 +0100, Terry Coles wrote: > > When a VPN client connects to the Web Server, in theory the web > > server would see that connection coming in from a 10.1.10.0/24 > > address, not a 192.168.0.0/24 one. So, it is a given that the > > Webserver has to be configured to accept connections from > > 10.1.10.0/24 clients. > So how would I do that? I always assumed that the VPN Server > included a router that would sort all that out. The iptables > output would indicate that it does. I suppose there is some nuance here; the connection would come from a 10.1.10.0/24 address, routed via the 192.168.0.0/24 address of the VPN server. So, the Webserver would see that 192.168.0. had forwarded it some traffic that originated from 10.1.10.x. If the VPN server were doing NAT routing/masquerading, as opposed to plain old routing, then the connection would appear to come directly from the VPN server's 192.168.0.0/24 address. I suppose the VPN server *could* be doing NAT routing, but that would be a little surprising to me, because I am not seeing how NAT routing would be beneficial in this set-up. But I only mentioned this in case you had configured the server to block connections that weren't from 192.168.0.0/24 addresses, so if you haven't done that then I can't see it being a concern. The only other thing that comes to mind on a brief reading of your response to me is that, if the web server isn't accessible by IP address, then it certainly isn't going to be accessible via hostname. So, as you say, the routing falls under suspicion. The finer points of iptables configuration are perhaps a bit lost on me, so while I can look at the broad-strokes of your config, and I think it seems OK, I could easily be missing some nuances that might send it off the rails. I suppose one thing to check is whether, while connected to the VPN, you have any other (conflicting) routes to 192.168.0.0/24. Or, indeed, whether there is a route to 192.168.0.0/24 at all. E.g. run $ ip route show on your VPN client computer and see where it thinks it should send traffic destined for 192.168.0.0/24. That raises the question of how the VPN client learns which networks it can route to via the VPN. Presumably it does learn something, since you can access the various non-Webserver devices in the 192.168.0.0/24 network. Unless that's happening by fluke. If there isn't a suitable route to 192.168.0.0/24 on the VPN client computer, then manually adding one temporarily might be a worthwhile experiment. It seems you've got me hooked on this puzzle, Terry. I was only going to write a few paragraphs here, to clarify my previous remarks! Patrick -- Next meeting: Online, Jitsi, Tuesday, 2022-05-03 20:00 Check to whom you are replying Meetings, mailing list, IRC, ... http://dorset.lug.org.uk New thread, don't hijack: mailto:dorset@mailman.lug.org.uk
Re: [Dorset] Wimborne Model Town Routing Problem
Patrick, Thanks for your extremely detailed response; it's taken me a while to get through it and I hope that I've understood what you are saying properly. BTW. I've learned quite a bit :-) See my responses below. On Sunday, 17 April 2022 15:17:04 BST Patrick Wigmore wrote: > If I understand you correctly, I think you are saying that each device > on the WMT Network is allocated an address in the 10.1.10.0/24 range. > This does not make sense. Why would the WMT Network devices need > 10.1.10.0/24 addresses, in addition to their 192.168.0.0/24 ones? I'm not sure where the information came from regarding the 10.1.10.0/24 address range; probably in one of my many conversations with the author of pistrong. It looks like I misunderstood him. > This also means that the VPN clients will not be getting told about > the 192.168.0.1 DNS server via DHCP, so they won't automatically use > it. This means their traffic won't get forwarded to the web server > automatically. If you wanted them to know about that DNS server, you > would need to configure the VPN server to tell them about it. They > won't discover it automatically via DHCP like an on-site network > client would. According to the author of pistrong they are. Here is a part of the Query/ Response session that pistrong generates during installation and configuration of the server: DNS Server for connected VPN clients: 192.168.0.1,8.8.8.8 The bit before the : is the Query and the rest is my response. You can see that the system has the information and should provide it to the client during negotiation. However, there appears to be no path to 192.168.0.1 from the client in use and so (I assume) the client drops it and only 8.8.8.8 remains. (However see below.) Early in the development process the author of pistrong suggested that I add the 8.8.8.8 to that response so that the client could still access the Internet while connected to the WMT Network via the VPN Server. > Be aware that VPN clients will sometimes use a VPN-provided DNS server > for EVERYTHING, which could have the effect of intercepting DNS > queries for traffic that has nothing to do with the VPN, which might > break networking for things that are running on the same machine as > the VPN client, and could cause a privacy issue. If possible, it may > be better to configure the VPN clients so that the WMT DNS server is > only used to query domain names that are part of the WMT network. The WMT DNS Server does only provide IP Addresses for the hosts on the WMT Network. Putting together your comment about privacy and my old IT Manager's reaction when someone at work 'bridged' the network, I see that this wasn't a particularly good idea. > So, when you said: > > The VPN Server doesn't know the IP Address of the > > Webserver, but it doesn't need to because all traffic should be > > forwarded to it. > > The second part of the statement was untrue. The VPN server DOES need > to know the IP address of the Webserver (assuming you want it to tell > its clients), because the automatic forwarding to the Webserver only > works for DHCP clients in the local network. I think there may be a misconception here. When I said forwarding, I meant that any queries in the 192.168.0.0/21 subnet should be forwarded to all the devices in that subnet. That would include the Webserver on 192.168.0.1. However for that to happen the VPN Client clearly needs to know that that IP Address provides a DNS Server and for some reason it either doesn't or it does and it can't get there (see below) > Do you mean that it does not work automatically, or do you mean that > clients logged in via the VPN cannot query this server at all. What > happens if you say explicitly which server to query, by doing: > > $ dig @192.168.0.1 [webserver domain name] > > or > > $ nslookup [webserver domain name] 192.168.0.1 > > on a device that is connected via the VPN? This is where I took one or two steps forward. Below is the console output during a VPN session. I've interspersed a few comments: terry@OptiPlex:~/Useful$ systemd-resolve --status Global Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported resolv.conf mode: foreign Link 2 (eno1) Current Scopes: DNS Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/ unsupported Current DNS Server: 192.168.1.1 DNS Servers: 192.168.1.1 This is the response immediately after I've connected from the client (my desktop machine). The client only knows about my local router which provides the DNS Service for machines logging on to my home network. I then logged on to VPN Server (I've obfuscated the username for security purposes because this is a public forum): terry@OptiPlex:~/Useful$ ssh @192.168.0.30 @192.168.0.30's password: Linux VPN-Server 5.15.32-v7l+ #1538 SMP Thu Mar 31 19:39:41 BST 2022 armv7l I then tried to run 'systemd-resolve --status' but this isn't supported so I did:
