The tcng language allows implementation-specific extensions via the pragma construct or parameter.
Pragmas can be added with the pragma parameter to devices, queuing disciplines, classes, filters, tunnels, filter elements, and policers. The pragma parameter is followed by a space-separated list of strings, each containing one or more non-blank printable characters.
Examples:
fifo (pragma "head-drop");
eth0 (pragma "rate=2Mbps" "mode=duplex")
Furthermore, a global pragma can be specified before the first device or queuing discipline with the pragma construct:
Example:
pragma ("debug=all");
The tcng language does not define the semantics of pragmas. An implementation may choose to ignore or refuse unrecognized pragmas, or pragmas in general, or it may fail in obscure ways in the presence of pragmas.