net-tc: extract skip classify bit from tc_verd

Packets sent by the IFB device skip subsequent tc classification.
A single bit governs this state. Move it out of tc_verd in
anticipation of removing that __u16 completely.

The new bitfield tc_skip_classify temporarily uses one bit of a
hole, until tc_verd is removed completely in a follow-up patch.

Remove the bit hole comment. It could be 2, 3, 4 or 5 bits long.
With that many options, little value in documenting it.

Introduce a helper function to deduplicate the logic in the two
sites that check this bit.

The field tc_skip_classify is set only in IFB on skbs cloned in
act_mirred, so original packet sources do not have to clear the
bit when reusing packets (notably, pktgen and octeon).

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 23 insertions, 22 deletions

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 082534e187fc..442c4c4a9606 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -81,7 +81,7 @@ static void ifb_ri_tasklet(unsigned long _txp)
                 u32 from = G_TC_FROM(skb->tc_verd);
 
                 skb->tc_verd = 0;
-                skb->tc_verd = SET_TC_NCLS(skb->tc_verd);
+                skb->tc_skip_classify = 1;
 
                 u64_stats_update_begin(&txp->tsync);
                 txp->tx_packets++;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b53c0cfd417e..570f60ec6cb4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -589,6 +589,7 @@ static inline bool skb_mstamp_after(const struct skb_mstamp *t1,
  *      @pkt_type: Packet class
  *      @fclone: skbuff clone status
  *      @ipvs_property: skbuff is owned by ipvs
+ *      @tc_skip_classify: do not classify packet. set by IFB device
  *      @peeked: this packet has been seen already, so stats have been
  *              done for it, don't do them again
  *      @nf_trace: netfilter packet trace flag
@@ -749,7 +750,9 @@ struct sk_buff {
 #ifdef CONFIG_NET_SWITCHDEV
         __u8                    offload_fwd_mark:1;
 #endif
-        /* 2, 4 or 5 bit hole */
+#ifdef CONFIG_NET_CLS_ACT
+        __u8                    tc_skip_classify:1;
+#endif
 
 #ifdef CONFIG_NET_SCHED
         __u16                   tc_index;       /* traffic control index */
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 498f81b229a4..857356f2d74b 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -418,6 +418,17 @@ static inline bool skb_at_tc_ingress(const struct sk_buff *skb)
 #endif
 }
 
+static inline bool skb_skip_tc_classify(struct sk_buff *skb)
+{
+#ifdef CONFIG_NET_CLS_ACT
+        if (skb->tc_skip_classify) {
+                skb->tc_skip_classify = 0;
+                return true;
+        }
+#endif
+        return false;
+}
+
 /* Reset all TX qdiscs greater then index of a device.  */
 static inline void qdisc_reset_all_tx_gt(struct net_device *dev, unsigned int i)
 {
diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index bba23dbb3ab6..1eed5d7509bc 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -22,8 +22,6 @@ bit 6,7: Where this packet was last seen
 1: on the Ingress
 2: on the Egress
 
-bit 8: when set --> Request not to classify on ingress. 
-
  *
  * */
 
@@ -36,10 +34,6 @@ bit 8: when set --> Request not to classify on ingress.
 #define AT_INGRESS      0x1
 #define AT_EGRESS       0x2
 
-#define TC_NCLS          _TC_MAKEMASK1(8)
-#define SET_TC_NCLS(v)   ( TC_NCLS | (v & ~TC_NCLS))
-#define CLR_TC_NCLS(v)   ( v & ~TC_NCLS)
-
 #define S_TC_AT          _TC_MAKE32(12)
 #define M_TC_AT          _TC_MAKEMASK(2,S_TC_AT)
 #define G_TC_AT(x)       _TC_GETVALUE(x,S_TC_AT,M_TC_AT)
diff --git a/net/core/dev.c b/net/core/dev.c
index 56818f7eab2b..e39e35d2e082 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4093,12 +4093,8 @@ another_round:
                         goto out;
         }
 
-#ifdef CONFIG_NET_CLS_ACT
-        if (skb->tc_verd & TC_NCLS) {
-                skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);
-                goto ncls;
-        }
-#endif
+        if (skb_skip_tc_classify(skb))
+                goto skip_classify;
 
         if (pfmemalloc)
                 goto skip_taps;
@@ -4128,8 +4124,8 @@ skip_taps:
 #endif
 #ifdef CONFIG_NET_CLS_ACT
         skb->tc_verd = 0;
-ncls:
 #endif
+skip_classify:
         if (pfmemalloc && !skb_pfmemalloc_protocol(skb))
                 goto drop;
 
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 2095c83ce773..f04715a57300 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -426,11 +426,9 @@ int tcf_action_exec(struct sk_buff *skb, struct tc_action **actions,
 {
         int ret = -1, i;
 
-        if (skb->tc_verd & TC_NCLS) {
-                skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);
-                ret = TC_ACT_OK;
-                goto exec_done;
-        }
+        if (skb_skip_tc_classify(skb))
+                return TC_ACT_OK;
+
         for (i = 0; i < nr_actions; i++) {
                 const struct tc_action *a = actions[i];
 
@@ -439,9 +437,8 @@ repeat:
                 if (ret == TC_ACT_REPEAT)
                         goto repeat;    /* we need a ttl - JHS */
                 if (ret != TC_ACT_PIPE)
-                        goto exec_done;
+                        break;
         }
-exec_done:
         return ret;
 }
 EXPORT_SYMBOL(tcf_action_exec);