Interfaces revisited

tcng supports various abbreviated forms of interface sections. All these abbreviations have in common that they either cause some restrictions, or may lead to ambiguities. The following abbreviations are possible:

• the keyword dev can be omitted, in which case the interface name must be a bare word or in double quotes, i.e. it is not possible to use an arbitrary string expression without the dev keyword.
• if not only dev, but also the name is omitted, the default interface eth0 (defined in config.h) or the default set with the command-line option -i is used.
• if omitting the interface name, also the curly braces around an interface section can be omitted, but this can lead to confusing ambiguities in variable and field definition scoping.

Examples:

/* no interface name, no curly braces */
fifo;

/* no interface name */
{
    fifo;
}

/* no "dev" keyword, name is bare word */
eth0 {
    fifo;
}

/* name contains special characters and must
   be quoted */
"funny:name" {
    fifo;
}

Interface names can also be followed by a parameter list in parentheses. This is necessary when using tags or pragmas, see sections 3.10 and 3.11.