Re: [net-next,v2] openvswitch: Add skb->len info to upcall.

The commit f2a4d086ed4c ("openvswitch: Add packet truncation support.")
introduces packet truncation before sending to userspace upcall receiver.
This patch passes up the skb->len before truncation so that the upcall
receiver knows the original packet size. Potentially this will be used
by sFlow, where OVS translates sFlow config header=N to a sample action,
truncating packet to N byte in kernel datapath. Thus, only N bytes instead
of full-packet size is copied from kernel to userspace, saving the
kernel-to-userspace bandwidth.

Signed-off-by: William Tu <redacted>
Cc: Pravin Shelar <redacted>

---
v1->v2:
- pass skb->len to userspace instead of cutlen
---
 include/uapi/linux/openvswitch.h |  2 ++
 net/openvswitch/actions.c        |  1 +
 net/openvswitch/datapath.c       | 15 +++++++++++++++
 net/openvswitch/datapath.h       |  2 ++
 4 files changed, 20 insertions(+)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 8274675..f9e204e 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h

@@ -166,6 +166,7 @@ enum ovs_packet_cmd {
  * output port is actually a tunnel port. Contains the output tunnel key
  * extracted from the packet as nested %OVS_TUNNEL_KEY_ATTR_* attributes.
  * @OVS_PACKET_ATTR_MRU: Present for an %OVS_PACKET_CMD_ACTION and
+ * @OVS_PACKET_ATTR_SKBLEN: Packet size before truncation.
  * %OVS_PACKET_ATTR_USERSPACE action specify the Maximum received fragment
  * size.
  *

@@ -185,6 +186,7 @@ enum ovs_packet_attr {
        OVS_PACKET_ATTR_PROBE,      /* Packet operation is a feature probe,
                                       error logging should be suppressed. */
        OVS_PACKET_ATTR_MRU,        /* Maximum received IP fragment size. */
+       OVS_PACKET_ATTR_SKBLEN,         /* Packet size before truncation. */
        __OVS_PACKET_ATTR_MAX
 };

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 1ecbd77..bb18ca1 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c

@@ -793,6 +793,7 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb,
        memset(&upcall, 0, sizeof(upcall));
        upcall.cmd = OVS_PACKET_CMD_ACTION;
        upcall.mru = OVS_CB(skb)->mru;
+       upcall.skblen = skb->len;

        for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
                 a = nla_next(a, &rem)) {

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 6739342..3866d87 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c

@@ -277,6 +277,7 @@ void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)
                upcall.cmd = OVS_PACKET_CMD_MISS;
                upcall.portid = ovs_vport_find_upcall_portid(p, skb);
                upcall.mru = OVS_CB(skb)->mru;
+               upcall.skblen = skb->len;

diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index ab85c1c..f87f526 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h

@@ -120,6 +120,7 @@ struct ovs_skb_cb {
  * counter.
  * @egress_tun_info: If nonnull, becomes %OVS_PACKET_ATTR_EGRESS_TUN_KEY.
  * @mru: If not zero, Maximum received IP fragment size.
+ * @skblen: The packet size before truncation.
  */
 struct dp_upcall_info {
        struct ip_tunnel_info *egress_tun_info;

@@ -129,6 +130,7 @@ struct dp_upcall_info {
        u32 portid;
        u8 cmd;
        u16 mru;
+       u32 skblen;
 };