Merge branch 'tc-skb-diet'

Willem de Bruijn says:

====================
convert tc_verd to integer bitfields

The skb tc_verd field takes up two bytes but uses far fewer bits.
Convert the remaining use cases to bitfields that fit in existing
holes (depending on config options) and potentially save the two
bytes in struct sk_buff.

This patchset is based on an earlier set by Florian Westphal and its
discussion (http://www.spinics.net/lists/netdev/msg329181.html).

Patches 1 and 2 are low hanging fruit: removing the last traces of
  data that are no longer stored in tc_verd.

Patches 3 and 4 convert tc_verd to individual bitfields (5 bits).

Patch 5 reduces TC_AT to a single bitfield,
  as AT_STACK is not valid here (unlike in the case of TC_FROM).

Patch 6 changes TC_FROM to two bitfields with clearly defined purpose.

It may be possible to reduce storage further after this initial round.
If tc_skip_classify is set only by IFB, testing skb_iif may suffice.
The L2 header pushing/popping logic can perhaps be shared with
AF_PACKET, which currently not pkt_type for the same purpose.

Changes:
  RFC -> v1
    - (patch 3): remove no longer needed label in tfc_action_exec
    - (patch 5): set tc_at_ingress at the same points as existing
                 SET_TC_AT calls

Tested ingress mirred + netem + ifb:

  ip link set dev ifb0 up
  tc qdisc add dev eth0 ingress
  tc filter add dev eth0 parent ffff: \
    u32 match ip dport 8000 0xffff \
    action mirred egress redirect dev ifb0
  tc qdisc add dev ifb0 root netem delay 1000ms
  nc -u -l 8000 &
  ssh $otherhost nc -u $host 8000

Tested egress mirred:

  ip link add veth1 type veth peer name veth2
  ip link set dev veth1 up
  ip link set dev veth2 up
  tcpdump -n -i veth2 udp and dst port 8000 &

  tc qdisc add dev eth0 root handle 1: prio
  tc filter add dev eth0 parent 1:0 \
    u32 match ip dport 8000 0xffff \
    action mirred egress redirect dev veth1
  tc qdisc add dev veth1 root netem delay 1000ms
  nc -u $otherhost 8000

Tested ingress mirred:

  ip link add veth1 type veth peer name veth2
  ip link add veth3 type veth peer name veth4

  ip netns add ns0
  ip netns add ns1

  for i in 1 2 3 4; do \
    NS=ns$((${i}%2)); \
    ip link set dev veth${i} netns ${NS}; \
    ip netns exec ${NS} \
      ip addr add dev veth${i} 192.168.1.${i}/24; \
    ip netns exec ${NS} \
      ip link set dev veth${i} up; \
  done

  ip netns exec ns0 tc qdisc add dev veth2 ingress
  ip netns exec ns0 \
    tc filter add dev veth2 parent ffff: \
      u32 match ip dport 8000 0xffff \
      action mirred ingress redirect dev veth4

  ip netns exec ns0 \
    tcpdump -n -i veth4 udp and dst port 8000 &
  ip netns exec ns1 \
    nc -u 192.168.1.2 8000
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 5 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b53c0cfd417e..3149a88de548 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -589,6 +589,10 @@ 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
+ *	@tc_at_ingress: used within tc_classify to distinguish in/egress
+ *	@tc_redirected: packet was redirected by a tc action
+ *	@tc_from_ingress: if tc_redirected, tc_at_ingress at time of redirect
  *	@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
@@ -598,7 +602,6 @@ static inline bool skb_mstamp_after(const struct skb_mstamp *t1,
  *	@nf_bridge: Saved data about a bridged frame - see br_netfilter.c
  *	@skb_iif: ifindex of device we arrived on
  *	@tc_index: Traffic control index
- *	@tc_verd: traffic control verdict
  *	@hash: the packet hash
  *	@queue_mapping: Queue mapping for multiqueue devices
  *	@xmit_more: More SKBs are pending for this queue
@@ -749,13 +752,15 @@ 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;
+	__u8			tc_at_ingress:1;
+	__u8			tc_redirected:1;
+	__u8			tc_from_ingress:1;
+#endif
 
 #ifdef CONFIG_NET_SCHED
 	__u16			tc_index;	/* traffic control index */
-#ifdef CONFIG_NET_CLS_ACT
-	__u16			tc_verd;	/* traffic control verdict */
-#endif
 #endif
 
 	union {