1 files changed, 58 insertions, 0 deletions
diff --git a/tests/e2e/dns_helpers.go b/tests/e2e/dns_helpers.go
new file mode 100644
index 0000000..38c42a1
--- /dev/null
+++ b/tests/e2e/dns_helpers.go
@@ -0,0 +1,58 @@
+package e2e
+
+import (
+	"net"
+	"testing"
+	"time"
+)
+
+// MockDNSServer is a minimal UDP server that responds to any DNS query
+// with a hardcoded A record for example.com.
+type MockDNSServer struct {
+	conn *net.UDPConn
+}
+
+func StartMockDNSServer(t *testing.T) (*MockDNSServer, int) {
+	addr, err := net.ResolveUDPAddr("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to resolve UDP address: %v", err)
+	}
+
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		t.Fatalf("failed to start mock DNS server: %v", err)
+	}
+
+	return &MockDNSServer{conn: conn}, conn.LocalAddr().(*net.UDPAddr).Port
+}
+
+func (s *MockDNSServer) Close() {
+	_ = s.conn.Close()
+}
+
+// ListenAndRespond runs in a loop and responds to the first valid-looking DNS query.
+// It returns the response as a channel to allow the test to synchronize.
+func (s *MockDNSServer) ListenAndRespond(timeout time.Duration) (chan bool, error) {
+	respChan := make(chan bool, 1)
+
+	go func() {
+		buf := make([]byte, 1024)
+		_ = s.conn.SetReadDeadline(time.Now().Add(timeout))
+		n, remoteAddr, err := s.conn.ReadFromUDP(buf)
+		if err != nil {
+			respChan <- false
+			return
+		}
+
+		if n < 4 {
+			respChan <- false
+			return
+		}
+
+		// Echo the packet back to the client as a basic "I heard you" confirmation.
+		_, _ = s.conn.WriteToUDP(buf[:n], remoteAddr)
+		respChan <- true
+	}()
+
+	return respChan, nil
+}