89941354_GnuTLS_3_4_3__Priority_Strings__Description
[Keyword] %DUMBFW [Description] 
will add a private extension with bogus data that make the client hello exceed 512 bytes. This avoids a black hole behavior in some firewalls. This is a non-standard TLS extension, use with care.
GnuTLS 3.4.3: Priority Strings
Description