dnsdist: Fix build on ancient GnuTLS versions (< 3.5.0)

diff --git a/pdns/tcpiohandler.cc b/pdns/tcpiohandler.cc
index 0bc0d7376f82308aa9e69c3c3ec17ea9b50ea0ee..0cac651ce2e049f19867eb1b7315ee13fe937d9b 100644 (file)
--- a/pdns/tcpiohandler.cc
+++ b/pdns/tcpiohandler.cc
@@ -1394,7 +1394,13 @@ public:
       value.size = proto.size();
       values.push_back(value);
     }
-    return gnutls_alpn_set_protocols(d_conn.get(), values.data(), values.size(), GNUTLS_ALPN_MANDATORY);
+    unsigned int flags = 0;
+#if GNUTLS_VERSION_NUMBER >= 0x030500
+    flags |= GNUTLS_ALPN_MANDATORY;
+#elif defined(GNUTLS_ALPN_MAND)
+    flags |= GNUTLS_ALPN_MAND;
+#endif
+    return gnutls_alpn_set_protocols(d_conn.get(), values.data(), values.size(), flags);
   }
 
 private: