On Thu, Jun 16, 2016 at 11:17 AM, William Tu <[email protected]> wrote:
> 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 <[email protected]>
> Cc: Pravin Shelar <[email protected]>
>
> ---
> 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
> };
>
skb is linux specific name. I do not think it should be used in OVS
datapath interface which is not platform specific.
> 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;
>
In case of GSO packet up call breaks the packet and sends multiple
upcall, therefore this packet length is not correct.
> 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;
same as output_userspace(), this could be gso packet.
...
...
> 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;
> };
>
There is no need to pass this as parameter, queue_userspace_packet()
has access to the packet length.
