标签：#wireguard

The tunnel comes up. wg show prints a recent handshake. The client has its address inside the tunnel. And not a single byte reaches the internet. Almost every guide answers this with "open UDP 51820 in the firewall". You already did that — it is why the handshake works at all. The problem is somewhere else, and UFW makes the distinction easy to miss: Entering a machine and traversing it are two different permissions. ufw allow 51820/udp lets packets arrive at the server. Your clients' traffic does not stop there — it goes through the box and out the public interface. That path lives in the FORWARD chain, which UFW denies by default and which no allow rule touches. The four things to check, in order 1. IP forwarding — and the file that overwrites the other file This is the one that costs hours, because the setting looks done. UFW loads its own sysctl file at startup, and it takes precedence over the system one. A value you carefully set in /etc/sysctl.conf can be silently overwritten on the next ufw enable . The right place is /etc/ufw/sysctl.conf : net / ipv4 / ip_forward = 1 net / ipv6 / conf / default / forwarding = 1 net / ipv6 / conf / all / forwarding = 1 Then check the effective value, not the file you just edited: sysctl net.ipv4.ip_forward 2. Forwarding, which is not the same as ingress Targeted, and the one to prefer: sudo ufw route allow in on wg0 out on eth0 Or globally, in /etc/default/ufw : DEFAULT_FORWARD_POLICY = "ACCEPT" The second opens forwarding for every interface. It is a good ten-second diagnostic and a poor permanent configuration. 3. NAT, which UFW never adds on its own Without it, packets leave carrying their tunnel address, which nothing on the internet knows how to answer. In /etc/ufw/before.rules , at the very top , before the *filter line: *nat :POSTROUTING ACCEPT [0:0] -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE COMMIT Two classic mistakes here: putting this block after *filter (it is then ignored), and copying eth0 without chec

This is the story of how a mundane complaint — "the VPN is slow" — turned into a US patent application. Not a granted patent. An application . I want to be precise about that from the start, because the distance between the two is the whole point of this post. It started with a slow VPN The company I work for had an internal VPN that everyone routed through. It lived in the Tokyo office, it was old, and it was not something I built. Then the complaints started arriving — from a lot of people, all saying the same thing: it's slow. I work from Thailand most of the time. That detail matters. If that aging box in Tokyo had fallen over, I would have been the person furthest from the power button, in the worst position to fix it. A slow VPN is annoying. An unreachable VPN, when you're a few thousand kilometers away, is a real problem. So I started moving it to the cloud. I stood up a WireGuard VPN — modern, fast, and something I could actually reason about and operate remotely instead of inheriting a black box. Down the WireGuard rabbit hole Around that time I was deep into building my own iPhone apps. So the cloud migration turned into a personal project on the side: I built my own server and wired WireGuard into an iPhone app of my own. And to do that properly, I started studying how WireGuard actually works under the hood — the Noise protocol, the handshake, the key exchange. That study is where everything else came from. I wasn't trying to invent anything. I was just trying to understand the thing I was now responsible for. The SYN flood that primed my brain Not long before, the same company had been hit with a SYN flood attack. If you've dealt with one, you know it lodges the mechanics of connection handshakes firmly in your head — the back-and-forth, the round trips, the cost of every "hello" before any real data moves. So I had handshakes on the brain. And then, reading through how WireGuard establishes a session, a thought stopped me: Wait — does it really handsha