Re: [RFC] ematch API, u32 ematch, nbyte ematch, basic classifier

[Thomas Graf <tgraf@xxxxxxx>]

* jamal <1104844753.1085.99.camel@xxxxxxxxxxxxxxxx> 2005-01-04 08:19
> On Tue, 2005-01-04 at 07:03, Thomas Graf wrote:
> >  change() (Optional)
> 
> My thinking is:
> It doesnt have to be simple 32 bit data.
> If i pass you a struct and tell you what length it is, then you as the
> classifier dont know need to know anything about it. You just store
> mystruct as data and datalen from the TLV. you then pass the datastruct
> to match() -  Of course the match() will have to know what that struct
> means.

That's exactly how it is, basically the logic is:

        if (ops->change) {
                err = ops->change(tp, data, datalen, m);
                if (err < 0)
                        goto errout;
        } else if (datalen > 0) {
                if (mh->flags & TCF_EM_SIMPLE) {
                        if (datalen != sizeof(u32))
                                goto errout;
                        m->data = *(u32 *) data;
                } else {
                        void *v = kmalloc(datalen, GFP_KERNEL);
                        if (v == NULL) {
                                err = -ENOBUFS;
                                goto errout;
                        }
                        memcpy(v, data, datalen);
                        m->data = (unsigned long) v;
                }
        }
        m->datalen = datalen;

> >  destroy() (Optional)
> >    Called if provided, otheriwse m->data is freed in ematch api unless
> >    TCF_EM_SIMPLE is set.
> 
> Again using the above logic, destroy becomes just kfree(mystruct)

Right, that's exactly how it is

        if (m->ops->destroy)
                m->ops->destroy(tp, m);
        else if (!(m->hdr.flags & TCF_EM_SIMPLE) && m->data)
                kfree((void *) m->data);


> >  dump() (Optional)
> >    Called if provided, otherwise m->data is dumped onto the skb with
> >    m->datalen as L. Special handling again for TCF_EM_SIMPLE.
> 
> and dump becomes a matter of looking at datalen and encapsulating
> mystruct in a TLV without thinking about what the content is.

Absolutely true, you know about the code before you read it ;->

        if (m->ops->dump) {
                if (m->ops->dump(skb, m) < 0)
                        goto rtattr_failure;
        } else if (m->hdr.flags & TCF_EM_SIMPLE) {
                u32 u = m->data;
                RTA_PUT_NOHDR(skb, sizeof(u32), &u);
        } else if (m->datalen > 0)
                RTA_PUT_NOHDR(skb, m->datalen, (void *) m->data);