[ovs-dev] [PATCH] datapath:backport: openvswitch: Add packet len info to upcall.

[William Tu]

Upstream commit:
    commit b95e5928fcc76d156352570858abdea7b2628efd
    Author: William Tu <u9012063 at gmail.com>
    Date:   Mon Jun 20 07:26:17 2016 -0700

    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 <u9012063 at gmail.com>
    Cc: Pravin Shelar <pshelar at nicira.com>
    Acked-by: Pravin B Shelar <pshelar at ovn.org>
    Signed-off-by: David S. Miller <davem at davemloft.net>

Tested-at: https://travis-ci.org/williamtu/ovs-travis/builds/140135299
Signed-off-by: William Tu <u9012063 at gmail.com>
---
 datapath/datapath.c                               | 13 ++++++++++++-
 datapath/linux/compat/include/linux/openvswitch.h |  2 ++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 169bbbb..b02807e 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -395,7 +395,8 @@ static size_t upcall_msg_size(const struct dp_upcall_info *upcall_info,
 {
 	size_t size = NLMSG_ALIGN(sizeof(struct ovs_header))
 		+ nla_total_size(hdrlen) /* OVS_PACKET_ATTR_PACKET */
-		+ nla_total_size(ovs_key_attr_size()); /* OVS_PACKET_ATTR_KEY */
+		+ nla_total_size(ovs_key_attr_size()) /* OVS_PACKET_ATTR_KEY */
+		+ nla_total_size(sizeof(unsigned int)); /* OVS_PACKET_ATTR_LEN */
 
 	/* OVS_PACKET_ATTR_USERDATA */
 	if (upcall_info->userdata)
@@ -530,6 +531,16 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		pad_packet(dp, user_skb);
 	}
 
+	/* Add OVS_PACKET_ATTR_LEN when packet is truncated */
+	if (cutlen > 0) {
+		if (nla_put_u32(user_skb, OVS_PACKET_ATTR_LEN,
+				skb->len)) {
+			err = -ENOBUFS;
+			goto out;
+		}
+		pad_packet(dp, user_skb);
+	}
+
 	/* Only reserve room for attribute header, packet data is added
 	 * in skb_zerocopy()
 	 */
diff --git a/datapath/linux/compat/include/linux/openvswitch.h b/datapath/linux/compat/include/linux/openvswitch.h
index b92d9ed..f1e80db 100644
--- a/datapath/linux/compat/include/linux/openvswitch.h
+++ b/datapath/linux/compat/include/linux/openvswitch.h
@@ -188,6 +188,7 @@ 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_LEN: Packet size before truncation.
  * %OVS_PACKET_ATTR_USERSPACE action specify the Maximum received fragment
  * size.
  *
@@ -207,6 +208,7 @@ 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_LEN,		/* Packet size before truncation. */
 	__OVS_PACKET_ATTR_MAX
 };
 
-- 
2.5.0