net-tc: convert tc_verd to integer bitfields

Extract the remaining two fields from tc_verd and remove the __u16
completely. TC_AT and TC_FROM are converted to equivalent two-bit
integer fields tc_at and tc_from. Where possible, use existing
helper skb_at_tc_ingress when reading tc_at. Introduce helper
skb_reset_tc to clear fields.

Not documenting tc_from and tc_at, because they will be replaced
with single bit fields in follow-on patches.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index e39e35d..8b5d6d0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3153,7 +3153,7 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
 	if (!cl)
 		return skb;
 
-	/* skb->tc_verd and qdisc_skb_cb(skb)->pkt_len were already set
+	/* skb->tc_at and qdisc_skb_cb(skb)->pkt_len were already set
 	 * earlier by the caller.
 	 */
 	qdisc_bstats_cpu_update(cl->q, skb);
@@ -3320,7 +3320,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
 
 	qdisc_pkt_len_init(skb);
 #ifdef CONFIG_NET_CLS_ACT
-	skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_EGRESS);
+	skb->tc_at = AT_EGRESS;
 # ifdef CONFIG_NET_EGRESS
 	if (static_key_false(&egress_needed)) {
 		skb = sch_handle_egress(skb, &rc, dev);
@@ -3920,7 +3920,7 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
 	}
 
 	qdisc_skb_cb(skb)->pkt_len = skb->len;
-	skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_INGRESS);
+	skb->tc_at = AT_INGRESS;
 	qdisc_bstats_cpu_update(cl->q, skb);
 
 	switch (tc_classify(skb, cl, &cl_res, false)) {
@@ -4122,9 +4122,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
 			goto out;
 	}
 #endif
-#ifdef CONFIG_NET_CLS_ACT
-	skb->tc_verd = 0;
-#endif
+	skb_reset_tc(skb);
 skip_classify:
 	if (pfmemalloc && !skb_pfmemalloc_protocol(skb))
 		goto drop;