Hi all home network administrators :) Haven't posted anything here since June, when I told you about Gatekeeper 1.1.0. Back then it was a pretty bare-bones (and maybe slightly buggy) DNS + DHCP server with a web UI with a list of LAN clients. Back at 1.1.0 Gatekeeper didn't even configure your LAN interface or set up NAT rules. It used to be something like dnsmasq - but with a web UI.
I've been improving it for the past couple of months - simplified it a lot, fixed bugs, optimized internals, improved the looks & added a bunch of quality-of-life features. Now it's a program that turns any linux machine into a home internet gateway. It's closer to OpenWRT in single executable file.
One big thing that happend was that I've attempted to replace the ubiquitous nft-based NAT (where the kernel processes the packets according to a rule-based script) with nfqueue (where the kernel sends the packet to userspace so that it can be altered arbitrarily). I've expected this to be buggy & slow. Well, it was hell to implement but it turns out that it's not slow at all. On the debug build my router can push 60GiB+ / second over TCP (over virtualized ethernet of course). And I'm not even using any io_uring magic yet. Quite honestly I don't even know how to explain it since it's slightly above the peak DDR4 transfer rate (I'm running dual channel DDR4-3200). Maybe the pages are not flushed to RAM & are only exchanged through CPU caches? Anyway I'm pretty excited because userspace access to all traffic opens a lot of new possibilities...
The first thing is NAT. By default Linux only supports symmetric NAT, which is pretty secure but is also fairly hard for the peer-to-peer protocols to pierce. There are some patches that make Linux full-cone but they're not, and are not expected to become a part of the mainline kernel (at least according to OpenWRT forums). Now, since we have access to every packet we can take care of this ourselves. We can create a couple hash tables to track connections, alter the source & destination IP, recomputing the checksums if necessary. Suddenly we can have full-cone NAT, on any linux machine, without patching the kernel! At runtime it's not as configurable as netfilter + conntrack but it's a whole lot simpler - since now we can use a general purpose programming language rather than netfilter rules.
Another cool feature that we can now have are truly realtime traffic graphs. Summary of each packet traversing the network boundary is immediately streamed to the connected web UIs over WebSocket. This is way faster than the alternatives based on reading some /proc/ or /sys/ files every couple of seconds. Gatekeeper also aggregates the traffic from the last 24 hours between each pair of hosts into a histogram with 100ms resolution and allow clients to view it, scroll through it, compute stats, download as JSON or CSV. You can retroactively check which device talked with what IP, at what time with unprecedented resolution.
My next step is going to be capturing the traffic that goes through into a 5MB circular buffer (separate buffer for each LAN client) & downloading it as Wireshark-compatible pcap files. Computationally it's almost free. IoT devices usually don't transmit a lot of data. 5MB may actually cover months of traffic for the simpler ones. If any device is did anything weird, it will finally be possible to investigate it - even after it already happened.
Long-term Gatekeeper could do even more. For example offer assistance in setting up TLS MITM, perform some online grouping / analysis on the live traffic.
I still have some ground work to do - like automatically setting up Wireless LAN, bridgidng multiple interfaces into a single one and I think there may be a bug that causes crashes when checking GitHub for updates. But I wanted to share it sooner rather than later. I hope that despite its imperfections some of you will find it useful!
(I've had some issues with cross-instance posting. This is attempt #6)
I don't think I fully understand how this is supposed to work. Am I correct in that this service acts as the gateway on the network? So clients would be configured to see this as the gateway, and this then subsequently pushes things through the real gateway (router)? Thus essentially everything (most things?) that the router does would be done by this instead?
It sounds like it's just an actual router, but I can't find any information if it actually can route any traffic.
Either way it seems like just setting up a real router with something like opnsense would be easier and more feature complete.
More features, yes. Easier? No. This project is aiming to be simpler than an OPNsense setup at the cost of advanced features.
According to the GitHub it can act as a router, OR you can leave your ISP router in place and have this act as a DNS and DHCP gateway. Please read the documentation before saying negative things in the comments.
OPNsense is ready to route pretty much after the default install, like any other off-the-shelf router. It’s only really complicated if you have complicated needs.
My questions exactly. Furthermore ISP router typically also have wifi, so wifi clients on that won't be even visible to this... please clarify is this is supposed to be yet another openwrt / router solution or what you're doing here... BUT I fucking love the UI :)
Right there with you on the UI. This would overlap in functionality with a lot of other items in my network, but I'm trying to find a reason to use it just so I can play with the UI.
Read the documentation.
"Generally speaking Gatekeeper needs to sit between your LAN network and the internet. It can either completely replace the router provided by ISP, or sit between the ISP router and your LAN network."