On Sun, 2006-08-01 at 18:46 +0100, Patrick McHardy wrote:
[..]
> >>int tcf_action_exec(struct sk_buff *skb, struct tc_action *act,
> >> struct tcf_result *res)
> >>{
> >>...
> >> ret = a->ops->act(&skb, a, res);
> >>
> >>The caller later continues to use the skb passed to tcf_action_exec
> >>and will crash if it was replaced.
> >>
> I think we discussed it at netconf.
Ok.
> Anyway, why do you want to keep this obvious broken behaviour?
I dont wanna keep it if it is broken Patrick;-> It seems to be a big
change at glance and normally i would like to run some serious tests
on something like this (this one you can actually test with a series of
mirred, pedit and gact while tcpdump is running - doesnt matter if
ingress or egress and then watch the hex dump of modified packets)
Ok, so lets go over the steps you described to see if i will make sense
of it.
Someone calls:
-> tcf_action_exec(skb ...)
---> ret = a->ops->act(&skb, a, res)
------> one or more actions
You are saying the user (I assume either caller of tcf_action_exec() or
an action) will crash if the skb was replaced. So lets start with
actions:
The "enviromental" rules are:
1) if you steal any packet thou shalt clone it (as in queueing it etc).
2) If you munge any packet thou shalt call skb_expand in the case
someone else is referencing the skb. Then you "own" it. You must also
tell us if it is ok to munge the packet (TC_OK2MUNGE)
3) dropping packets you dont own is a nono. You simply return
TC_ACT_SHOT
The "enviromental" rules for callers of actions (qdiscs etc) are:
thou art responsible for freeing anything returned as being
TC_ACT_SHOT/STOLEN/QUEUED otherwise all is great.
cheers,
jamal
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