Put the whole unfurl, lookups included, under one deadline

The deadline in Opengraph::Fetch started after the lookup of the pasted
host, and an unfurl looks up more hosts outside any fetch: the canonical
URL's, and the image's, once to check its content type and again to
validate it. Each of those waits as long as the resolver takes to give
up. Move the deadline up to UnfurlLinksController, around everything the
link leads to; Opengraph::Fetch keeps its per-operation timeouts and
makes no retries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bj8KnxpTf9sj2Ysa8aLAVa

test/controllers/unfurl_links_controller_test.rb

@@ -75,7 +75,94 @@ class UnfurlLinksControllerTest < ActionDispatch::IntegrationTest
     assert_equal "Hey!", JSON.parse(response.body)["title"]
   end
 
+  test "create gives up on a host that accepts the connection and never answers" do
+    with_local_host do |url, connections|
+      stub_const(Opengraph::Fetch, :TIMEOUT, 0.2.seconds) do
+        assert_unfurls_nothing_within(1.second) { post unfurl_link_url, params: { url: url } }
+      end
+      assert_equal 1, connections.size, "the GET is not retried"
+    end
+  end
+
+  test "create gives up on headers that trickle in past the deadline" do
+    trickle_headers = ->(client) do
+      client.write "HTTP/1.1 200 OK\r\nX-Padding: "
+      100.times { client.write "x"; sleep 0.05 }
+      client.write "\r\nContent-Type: text/html\r\nContent-Length: 2\r\n\r\nok"
+    end
+
+    with_local_host(trickle_headers) do |url|
+      stub_const(UnfurlLinksController, :DEADLINE, 0.5.seconds) do
+        assert_unfurls_nothing_within(1.5.seconds) { post unfurl_link_url, params: { url: url } }
+      end
+    end
+  end
+
+  test "create gives up on a body that trickles in past the deadline" do
+    trickle_body = ->(client) do
+      client.write "HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nContent-Length: 100\r\n\r\n"
+      100.times { client.write "x"; sleep 0.05 }
+    end
+
+    with_local_host(trickle_body) do |url|
+      stub_const(UnfurlLinksController, :DEADLINE, 0.5.seconds) do
+        assert_unfurls_nothing_within(1.5.seconds) { post unfurl_link_url, params: { url: url } }
+      end
+    end
+  end
+
+  test "create gives up on redirects that keep coming past the deadline" do
+    stub_dns_resolution("1.2.3.4")
+    WebMock.stub_request(:get, "https://www.example.com/").to_return do
+      sleep 0.2
+      { status: 302, headers: { location: "https://www.example.com/" } }
+    end
+
+    stub_const(UnfurlLinksController, :DEADLINE, 0.5.seconds) do
+      assert_unfurls_nothing_within(1.second) { post unfurl_link_url, params: { url: "https://www.example.com" } }
+    end
+  end
+
+  test "create gives up on a host name that takes too long to look up" do
+    Resolv.stubs(:getaddresses).with { sleep 2 }.returns([ "1.2.3.4" ]) # each lookup takes 2 s
+    WebMock.stub_request(:get, "https://www.example.com/").to_return(status: 200, body: "<html></html>", headers: { content_type: "text/html" })
+
+    stub_const(UnfurlLinksController, :DEADLINE, 0.5.seconds) do
+      assert_unfurls_nothing_within(1.second) { post unfurl_link_url, params: { url: "https://www.example.com" } }
+    end
+  end
+
   private
+    # A real socket, because WebMock reads the whole response before the code under test sees any of it.
+    # The guard lets the local address through, as it would a public one.
+    def with_local_host(respond = ->(client) { })
+      server = TCPServer.new("127.0.0.1", 0)
+      connections = Queue.new
+      Thread.new do
+        loop do
+          client = server.accept
+          connections << client
+          client.readpartial(1024)
+          respond.call(client)
+        end
+      rescue IOError, SystemCallError
+      end
+
+      RestrictedHTTP::PrivateNetworkGuard.stubs(:resolve).returns("127.0.0.1")
+      WebMock.disable!
+      yield "http://www.example.com:#{server.addr[1]}/", connections
+    ensure
+      WebMock.enable!
+      server&.close
+    end
+
+    def assert_unfurls_nothing_within(limit)
+      started = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      yield
+      assert_response :no_content
+      assert_operator Process.clock_gettime(Process::CLOCK_MONOTONIC) - started, :<, limit
+    end
+
     def stub_successful_request(url: "https://www.example.com/", title: "Hey!", description: "desc..")
       WebMock.stub_request(:get, url).to_return(
         status: 200,