[NET_SCHED]: act_api: qdisc internal reclassify support

The behaviour of NET_CLS_POLICE for TC_POLICE_RECLASSIFY was to return
it to the qdisc, which could handle it internally or ignore it. With
NET_CLS_ACT however, tc_classify starts over at the first classifier
and never returns it to the qdisc. This makes it impossible to support
qdisc-internal reclassification, which in turn makes it impossible to
remove the old NET_CLS_POLICE code without breaking compatibility since
we have two qdiscs (CBQ and ATM) that support this.

This patch adds a tc_classify_compat function that handles
reclassification the old way and changes CBQ and ATM to use it.

This again is of course not fully backwards compatible with the previous
NET_CLS_ACT behaviour. Unfortunately there is no way to fully maintain
compatibility *and* support qdisc internal reclassification with
NET_CLS_ACT, but this seems like the better choice over keeping the two
incompatible options around forever.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index ccee10d..37ae6d1 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -396,8 +396,9 @@
 	    !(flow = (struct atm_flow_data *)atm_tc_get(sch, skb->priority)))
 		for (flow = p->flows; flow; flow = flow->next)
 			if (flow->filter_list) {
-				result = tc_classify(skb, flow->filter_list,
-						     &res);
+				result = tc_classify_compat(skb,
+							    flow->filter_list,
+							    &res);
 				if (result < 0)
 					continue;
 				flow = (struct atm_flow_data *)res.class;
@@ -420,6 +421,12 @@
 		case TC_ACT_SHOT:
 			kfree_skb(skb);
 			goto drop;
+		case TC_POLICE_RECLASSIFY:
+			if (flow->excess)
+				flow = flow->excess;
+			else
+				ATM_SKB(skb)->atm_options |= ATM_ATMOPT_CLP;
+			break;
 		}
 #elif defined(CONFIG_NET_CLS_POLICE)
 		switch (result) {