Protocol Registration

For this callback, only the proto argument is filled in by the caller. Neither an event nor a hook name can be meaningfully supplied at this point. In this example function, only events that announce the registration of the IPv4 protocol are being looked for.

The next step in this function is to discover when events are added to the IPv4 protocol by using the net_protocol_notify_register() interface to register the mynewevent() function.

static int
mynewproto(hook_notify_cmd_t cmd, void *arg, const char *proto,
    const char *event, const char *hook)
{
    mytype_t *ctx = arg;

    if (strcmp(proto, NHF_INET) != 0)
        return (0);

    switch (cmd) {
        case HN_REGISTER :
            ctx->inet = net_protocol_lookup(s->id, proto);
            net_protocol_notify_register(s->inet, mynewevent, ctx);
            break;
        case HN_UNREGISTER :
        case HN_NONE :
            break;
    }
    return (0);
}

The table below lists all three protocols that could be expected to be seen with the mynewproto() callback. New protocols could be added in the future, so you must safely fail (return the value 0) any unknown protocols.