Re: [PATCH] openvswitch: Add packet truncation support.

On Thu, Jun 9, 2016 at 1:02 PM, William Tu [off-list ref] wrote:

quoted

quoted

        /* The only known usage of sample action is having a single
user-space
+        * action, or having a truncate action followed by a single
user-space
         * action. Treat this usage as a special case.
         * The output_userspace() should clone the skb to be sent to the
         * user space. This skb will be consumed by its caller.
         */
+       if (unlikely(nla_type(a) == OVS_ACTION_ATTR_TRUNC)) {
+               struct ovs_action_trunc *trunc = nla_data(a);
+
+               OVS_CB(skb)->cutlen = skb->len > trunc->max_len ?
+                                               skb->len -
trunc->max_len : 0;

There is no need to initialize the cutlen to zero if max-len is
greater then skb len. it should be already zero.

quoted

+               a = nla_next(a, &rem);
+       }
+

There cutlen is set in skb cb, but next action could be other than
userspace, in that case cutlen is leaked to remain action list.

Thanks! I will fix it.

Thinking about cutlen to the remaining action list, should we consider the
truncate and output in sample action? ex:  "sample(truncate(64), output:2)"

The patch already covers it. sample calls add_deferred_actions() which
would execute nested set of actions later on.