On Thu, Jun 9, 2016 at 4:57 PM, William Tu <u9012...@gmail.com> wrote:
> The patch adds a new OVS action, OVS_ACTION_ATTR_TRUNC, in order to
> truncate packets. A 'max_len' is added for setting up the maximum
> packet size, and a 'cutlen' field is to record the number of bytes
> to trim the packet when the packet is outputting to a port, or when
> the packet is sent to userspace.
>
> Signed-off-by: William Tu <u9012...@gmail.com>
> ---
> v1 -> v2:
> - Use 32 bits cutlen and fix unnecessary cutlen initilization.
> - Fix cutlen leaks to remaining actions under sample action.
> - In queue_userspace_packet, don't extract hlen when using skb_zerocopy.
> ---
> include/uapi/linux/openvswitch.h | 7 +++++++
> net/openvswitch/actions.c | 34 ++++++++++++++++++++++++++++++----
> net/openvswitch/datapath.c | 27 ++++++++++++++++-----------
> net/openvswitch/datapath.h | 5 ++++-
> net/openvswitch/flow_netlink.c | 9 +++++++++
> net/openvswitch/vport.c | 1 +
> 6 files changed, 67 insertions(+), 16 deletions(-)
...
...
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 9a3eb7a..64dbc80 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -750,6 +750,10 @@ static void do_output(struct datapath *dp, struct
> sk_buff *skb, int out_port,
>
> if (likely(vport)) {
> u16 mru = OVS_CB(skb)->mru;
> + u32 cutlen = OVS_CB(skb)->cutlen;
> +
> + if (cutlen > 0)
> + pskb_trim(skb, skb->len - cutlen);
>
Lets add check min packet length. also add unlikely annotation to the
condition.
> if (likely(!mru || (skb->len <= mru + ETH_HLEN))) {
> ovs_vport_send(vport, skb);
...
...
> @@ -1059,8 +1077,16 @@ static int do_execute_actions(struct datapath *dp,
> struct sk_buff *skb,
> prev_port = nla_get_u32(a);
> break;
>
> + case OVS_ACTION_ATTR_TRUNC: {
> + struct ovs_action_trunc *trunc = nla_data(a);
> +
> + if (skb->len > trunc->max_len)
> + OVS_CB(skb)->cutlen = skb->len -
> trunc->max_len;
> + break;
> + }
> +
> case OVS_ACTION_ATTR_USERSPACE:
> - output_userspace(dp, skb, key, a, attr, len);
> + output_userspace(dp, skb, key, a, attr, len, 0);
Need to pass cutlen here to truncate packet for userspace action. Also
reset cutlen to zero for the skb after this action is executed.
> break;
>
> case OVS_ACTION_ATTR_HASH:
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 856bd8d..26f947e 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
...
...
>
> static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
> const struct sw_flow_key *key,
> - const struct dp_upcall_info *upcall_info)
> + const struct dp_upcall_info *upcall_info,
> + uint32_t cutlen)
> {
> struct ovs_header *upcall;
> struct sk_buff *nskb = NULL;
> @@ -515,9 +520,9 @@ static int queue_userspace_packet(struct datapath *dp,
> struct sk_buff *skb,
> err = -ENOBUFS;
> goto out;
> }
> - nla->nla_len = nla_attr_size(skb->len);
> + nla->nla_len = nla_attr_size(skb->len - cutlen);
>
> - err = skb_zerocopy(user_skb, skb, skb->len, hlen);
> + err = skb_zerocopy(user_skb, skb, skb->len - cutlen, hlen);
> if (err)
> goto out;
If packet is truncated there is no need to allocate buffer according
to full packet packet length.
