``` /** 11c. validate pluggable transports configuration if we need to */ if (!has_validated_pt && (options->Bridges || options->ClientTransportPlugin)) { if (validate_pluggable_transports_config() == 0) { has_validated_pt = 1; } } ``` where `has_validated_pt` is a static variable. This means that after getting set to `1`, `validate_pluggable_transports_config()` will never be called again (even after a SIGHUP).