datapath: Get packet metadata from userspace in odp_packet_cmd_execute().

Until now, the tun_id and in_port have been lost when a packet is sent from
the kernel to userspace and then back to the kernel.  I didn't think that
this was a problem, but recent behavior made me look closer and see that
it makes a difference if sFlow is turned on or if an
ODP_ATTR_ACTION_CONTROLLER action is present.  We could possibly kluge
around those, but for future-proofing it seems better to pass the packet
metadata from userspace to the kernel.  That is what this commit does.

This commit introduces a user-kernel protocol break.  We could avoid that,
if it is desirable, by making ODP_PACKET_ATTR_KEY optional for
ODP_PACKET_CMD_EXECUTE commands.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>

lib/dpif-netdev.c

@@ -944,6 +944,7 @@ dpif_netdev_flow_dump_done(const struct dpif *dpif OVS_UNUSED, void *state_)
 
 static int
 dpif_netdev_execute(struct dpif *dpif,
+                    const struct nlattr *key_attrs, size_t key_len,
                     const struct nlattr *actions, size_t actions_len,
                     const struct ofpbuf *packet)
 {
@@ -975,7 +976,10 @@ dpif_netdev_execute(struct dpif *dpif,
          * if we don't. */
         copy = *packet;
     }
+
     flow_extract(&copy, 0, -1, &key);
+    dpif_netdev_flow_from_nlattrs(key_attrs, key_len, &key);
+
     error = dp_netdev_execute_actions(dp, &copy, &key, actions, actions_len);
     if (mutates) {
         ofpbuf_uninit(&copy);