Recipe: routing certain domains through a proxy

Domains (and their subdomains) listed in file domains.txt will be redirected into a proxy http://192.168.88.1:8001, all other connections go directly.

Run dumbproxy like this:

dumbproxy -js-proxy-router routeDomains.js

routeDomains.js:

function normalizeDomain(d) {
  return d.replace(/\.$/, "").toLowerCase();
}

const domains = new Set();
readFile("domains.txt")
  .split(/\r?\n|\r|\n/g)
  .forEach(line => {
    line = line.replace(/#.*$/, "").trim(); // strip comment part and whitespace
    line = normalizeDomain(line); // normalize domain name
    if (line !== "") {
      domains.add(line);
    }
  });
//print("loaded domains:");
//print(JSON.stringify(Array.from(domains)));

function getProxy(req, dst, username) {
  let host = normalizeDomain(dst.originalHost);
  do {
    if (domains.has(host)) return "http://192.168.88.1:8001"; // proxy
    host = host.replace(/^[^\.]*.|[^\.]*$/, "");
  } while (host);
  return ""; // bypass
}