On 13/10/2026 11:01, Eelco Chaudron wrote:
+/* Build a set of alternative actions to exercise the alt_actions support in
+ * the netdev_hw_post_process() API. The dummy implementation returns
+ * alternative actions only when the action list consists solely of
+ * OVS_ACTION_ATTR_OUTPUT actions, and at least one egress port is not of
+ * type dummy-pmd. In that case, the dummy-pmd outputs are handled in
+ * 'hardware', while the non-dummy-pmd outputs are returned as alternative
+ * actions to be executed by the PMD thread. */
+static struct offload_actions *
+dummy_build_alt_actions(const struct dpif_offload *offload_,
+ odp_port_t in_odp,
+ const struct nlattr *actions,
+ size_t actions_len)
+{
+ struct offload_actions *alt_actions = NULL;
+ const struct nlattr *nla;
+ struct ofpbuf buf;
+ size_t left;
+
+ ofpbuf_init(&buf, 0);
+
+ NL_ATTR_FOR_EACH (nla, left, actions, actions_len) {
+ enum ovs_action_attr action = nl_attr_type(nla);
+ struct dummy_offload_port *out_port;
+ odp_port_t out_odp;
+
+ if (action != OVS_ACTION_ATTR_OUTPUT) {
+ goto out;
+ }
+
+ out_odp = nl_attr_get_odp_port(nla);
+ out_port = dummy_offload_get_port_by_odp_port(offload_, out_odp);
+ if (out_odp != in_odp
+ && (!out_port
+ || strcmp("dummy-pmd",
+ netdev_get_type(out_port->pm_port.netdev)))) {
+ ofpbuf_put(&buf, nla, NLA_ALIGN(nla->nla_len));
I still think it can be simplified. Here you build a struct ofpbuf, that you
copy from the actions to. Later, you copy this to alt_actions. All we need is
to detect this case, then copy actions (minus the first one) to alt_actions.
Your suggestion assumes the non-dummy-pmd ports are always at the
start of the list. We support mixed port lists like:
p1(non-pmd), p2(pmd), p3(non-pmd), p4(pmd)
In this case we can not simply copy everything after the first
action, as the pmd ports (p2, p4) must still be handled in hardware
and should not be part of the alt_actions. However I reworked the
code to avoid the copy, by using xrealloc() instead of an ofpbuf.
Will send this in a v3 later.
In practice, since we don't change the order (at least try) of the
actions, we can have a "actions=port_ol1,port_non_ol1,port_ol2". In HW
the offload will do only "port_ol1" and the rest will be done in SW
since port_non_ol1 is not offloadable.
BTW, this is a feature we abandoned at the time (because we didn't have
alt_actions, :)), but also it was not very important.
The real use case is for CT, but we don't have this part yet.
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