Index: frontend/node_modules/default-gateway/linux.js
===================================================================
--- frontend/node_modules/default-gateway/linux.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/default-gateway/linux.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,57 @@
+"use strict";
+
+const {isIP} = require("net");
+const {networkInterfaces} = require("os");
+const execa = require("execa");
+
+const args = {
+  v4: ["-4", "r"],
+  v6: ["-6", "r"],
+};
+
+const parse = (stdout, family) => {
+  let result;
+
+  (stdout || "").trim().split("\n").some(line => {
+    const results = /default( via .+?)?( dev .+?)( |$)/.exec(line) || [];
+    const gateway = (results[1] || "").substring(5);
+    const iface = (results[2] || "").substring(5);
+    if (gateway && isIP(gateway)) { // default via 1.2.3.4 dev en0
+      result = {gateway, interface: (iface ? iface : null)};
+      return true;
+    } else if (iface && !gateway) { // default via dev en0
+      const interfaces = networkInterfaces();
+      const addresses = interfaces[iface];
+      if (!addresses || !addresses.length) return;
+
+      addresses.some(addr => {
+        if (addr.family.substring(2) === family && isIP(addr.address)) {
+          result = {gateway: addr.address, interface: (iface ? iface : null)};
+          return true;
+        }
+      });
+    }
+  });
+
+  if (!result) {
+    throw new Error("Unable to determine default gateway");
+  }
+
+  return result;
+};
+
+const promise = async family => {
+  const {stdout} = await execa("ip", args[family]);
+  return parse(stdout, family);
+};
+
+const sync = family => {
+  const {stdout} = execa.sync("ip", args[family]);
+  return parse(stdout, family);
+};
+
+module.exports.v4 = () => promise("v4");
+module.exports.v6 = () => promise("v6");
+
+module.exports.v4.sync = () => sync("v4");
+module.exports.v6.sync = () => sync("v6");