On Fri, 2007-09-21 at 13:43 +0800, Peter Memishian wrote:
> To do this in a manner that doesn't massively interfere
> with forwarding performance (e.g., since the packet isn't for us, we
> need to decide whether to forward it or rewrite to be for us), it
> seems like we'd need an SIOCSLIFDHCPINIT ioctl that the client would
> use to enable this behavior when necessary on an interface[2] (which
> would e.g. set ill->ill_dhcp_init), and then we'd have to add one
> additional check to the fastpath stanza in ip_input() -- e.g.:
>
> if (!is_system_labeled() &&
> !ipst->ips_ip_cgtp_filter && ipp_action_count == 0 &&
> opt_len == 0 && ipha->ipha_protocol != IPPROTO_RSVP &&
> !ll_multicast && !CLASSD(dst) && !ill->ill_dhcp_init) {
> ^^^^^^^^^^^^^^^^^^^
>
> Unfortunately, even this single check will impact general networking
> performance especially for small packets,
actually, it looks like two of the tests (is_system_labeled() and
ipp_action_count) are global variables while ipst is the zone-global
ipstack structure. Any way we could precompute the AND of a few of
those and your SIOCLIFDHCPINIT bit into a single per-ill "stay off the
fast-path" bit (and re-compute it whenever one of them changes?)
- Bill
