Put the caller, site and route on every request's span and log line

src/http/request-fields.test.ts

@@ -0,0 +1,55 @@
+import assert from "node:assert/strict";
+import type { IncomingMessage } from "node:http";
+import { test } from "node:test";
+import { clientAddress, parseTrustedProxies, requestFields } from "./request-fields.ts";
+
+const proxies = parseTrustedProxies(["10.0.0.0/8", "192.168.1.5", "fd00::/8"]);
+const none = parseTrustedProxies([]);
+
+test("clientAddress: the socket peer, unless the peer is a listed proxy", () => {
+  assert.equal(clientAddress("203.0.113.9", "198.51.100.1", proxies), "203.0.113.9"); // header ignored from a stranger
+  assert.equal(clientAddress("10.1.2.3", "198.51.100.1", proxies), "198.51.100.1");
+  assert.equal(clientAddress("10.1.2.3", "198.51.100.1", none), "10.1.2.3"); // nothing trusted by default
+  assert.equal(clientAddress("192.168.1.5", undefined, proxies), "192.168.1.5"); // trusted peer, no header
+  assert.equal(clientAddress(undefined, "198.51.100.1", proxies), undefined);
+});
+
+test("clientAddress: walks the chain from the right, so a forged leftmost entry is not believed", () => {
+  assert.equal(clientAddress("10.0.0.1", "6.6.6.6, 198.51.100.1, 10.0.0.2", proxies), "198.51.100.1");
+  assert.equal(clientAddress("10.0.0.1", "10.0.0.7, 10.0.0.2", proxies), "10.0.0.7"); // every hop trusted → the origin
+});
+
+test("clientAddress: a malformed hop or a mapped IPv4 peer never yields garbage", () => {
+  assert.equal(clientAddress("10.0.0.1", "not-an-ip", proxies), "10.0.0.1");
+  assert.equal(clientAddress("::ffff:10.0.0.1", "198.51.100.1", proxies), "198.51.100.1");
+  assert.equal(clientAddress("::ffff:203.0.113.9", undefined, none), "203.0.113.9");
+  assert.equal(clientAddress("fd00::1", "2001:db8::7", proxies), "2001:db8::7");
+});
+
+test("parseTrustedProxies: refuses an entry that is not an IP or a CIDR range", () => {
+  for (const bad of ["proxy.internal", "10.0.0.0/33", "10.0.0.0/x", "::1/129", ""]) {
+    assert.throws(() => parseTrustedProxies([bad]), /TRUSTED_PROXIES/, bad);
+  }
+});
+
+const request = (headers: Record<string, string>, remoteAddress = "203.0.113.9", url = "/a/b?token=secret", method = "POST") =>
+  ({ headers, method, socket: { remoteAddress }, url }) as unknown as IncomingMessage;
+
+test("requestFields: OpenTelemetry names for the caller, the site and the request, without the query", () => {
+  const fields = requestFields(request({ host: "Example.com:8080", "user-agent": "TV/1.0" }), none);
+  assert.deepEqual(fields, {
+    "client.address": "203.0.113.9",
+    "http.request.method": "POST",
+    "server.address": "example.com",
+    "url.path": "/a/b",
+    "user_agent.original": "TV/1.0",
+  });
+});
+
+test("requestFields: drops what the request lacks or sent malformed, and reads X-Forwarded-For only via a trusted peer", () => {
+  assert.deepEqual(requestFields(request({ host: "bad host" }, "10.0.0.1", "/"), proxies), {
+    "client.address": "10.0.0.1", "http.request.method": "POST", "url.path": "/",
+  });
+  const fields = requestFields(request({ "x-forwarded-for": "198.51.100.1" }, "10.0.0.1"), proxies);
+  assert.equal(fields["client.address"], "198.51.100.1");
+});