openvswitch: Add packet truncation support.

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

5 files changed, 67 insertions, 17 deletions

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 9a3eb7a0ebf4..1ecbd7715f6d 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -750,6 +750,14 @@ 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 (unlikely(cutlen > 0)) {
+                        if (skb->len - cutlen > ETH_HLEN)
+                                pskb_trim(skb, skb->len - cutlen);
+                        else
+                                pskb_trim(skb, ETH_HLEN);
+                }
 
                 if (likely(!mru || (skb->len <= mru + ETH_HLEN))) {
                         ovs_vport_send(vport, skb);
@@ -775,7 +783,8 @@ static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port,
 
 static int output_userspace(struct datapath *dp, struct sk_buff *skb,
                             struct sw_flow_key *key, const struct nlattr *attr,
-                            const struct nlattr *actions, int actions_len)
+                            const struct nlattr *actions, int actions_len,
+                            uint32_t cutlen)
 {
         struct dp_upcall_info upcall;
         const struct nlattr *a;
@@ -822,7 +831,7 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb,
                 } /* End of switch. */
         }
 
-        return ovs_dp_upcall(dp, skb, key, &upcall);
+        return ovs_dp_upcall(dp, skb, key, &upcall, cutlen);
 }
 
 static int sample(struct datapath *dp, struct sk_buff *skb,
@@ -832,6 +841,7 @@ static int sample(struct datapath *dp, struct sk_buff *skb,
         const struct nlattr *acts_list = NULL;
         const struct nlattr *a;
         int rem;
+        u32 cutlen = 0;
 
         for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
                  a = nla_next(a, &rem)) {
@@ -858,13 +868,24 @@ static int sample(struct datapath *dp, struct sk_buff *skb,
                 return 0;
 
         /* The only known usage of sample action is having a single user-space
+         * action, or having a truncate action followed by a single user-space
          * action. Treat this usage as a special case.
          * The output_userspace() should clone the skb to be sent to the
          * user space. This skb will be consumed by its caller.
          */
+        if (unlikely(nla_type(a) == OVS_ACTION_ATTR_TRUNC)) {
+                struct ovs_action_trunc *trunc = nla_data(a);
+
+                if (skb->len > trunc->max_len)
+                        cutlen = skb->len - trunc->max_len;
+
+                a = nla_next(a, &rem);
+        }
+
         if (likely(nla_type(a) == OVS_ACTION_ATTR_USERSPACE &&
                    nla_is_last(a, rem)))
-                return output_userspace(dp, skb, key, a, actions, actions_len);
+                return output_userspace(dp, skb, key, a, actions,
+                                        actions_len, cutlen);
 
         skb = skb_clone(skb, GFP_ATOMIC);
         if (!skb)
@@ -1051,6 +1072,7 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
                         if (out_skb)
                                 do_output(dp, out_skb, prev_port, key);
 
+                        OVS_CB(skb)->cutlen = 0;
                         prev_port = -1;
                 }
 
@@ -1059,8 +1081,18 @@ 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, OVS_CB(skb)->cutlen);
+                        OVS_CB(skb)->cutlen = 0;
                         break;
 
                 case OVS_ACTION_ATTR_HASH:
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 856bd8dba676..673934295333 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -137,10 +137,12 @@ EXPORT_SYMBOL_GPL(lockdep_ovsl_is_held);
 static struct vport *new_vport(const struct vport_parms *);
 static int queue_gso_packets(struct datapath *dp, struct sk_buff *,
                              const struct sw_flow_key *,
-                             const struct dp_upcall_info *);
+                             const struct dp_upcall_info *,
+                             uint32_t cutlen);
 static int queue_userspace_packet(struct datapath *dp, struct sk_buff *,
                                   const struct sw_flow_key *,
-                                  const struct dp_upcall_info *);
+                                  const struct dp_upcall_info *,
+                                  uint32_t cutlen);
 
 /* Must be called with rcu_read_lock. */
 static struct datapath *get_dp_rcu(struct net *net, int dp_ifindex)
@@ -275,7 +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;
-                error = ovs_dp_upcall(dp, skb, key, &upcall);
+                error = ovs_dp_upcall(dp, skb, key, &upcall, 0);
                 if (unlikely(error))
                         kfree_skb(skb);
                 else
@@ -300,7 +302,8 @@ out:
 
 int ovs_dp_upcall(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 dp_stats_percpu *stats;
         int err;
@@ -311,9 +314,9 @@ int ovs_dp_upcall(struct datapath *dp, struct sk_buff *skb,
         }
 
         if (!skb_is_gso(skb))
-                err = queue_userspace_packet(dp, skb, key, upcall_info);
+                err = queue_userspace_packet(dp, skb, key, upcall_info, cutlen);
         else
-                err = queue_gso_packets(dp, skb, key, upcall_info);
+                err = queue_gso_packets(dp, skb, key, upcall_info, cutlen);
         if (err)
                 goto err;
 
@@ -331,7 +334,8 @@ err:
 
 static int queue_gso_packets(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)
 {
         unsigned short gso_type = skb_shinfo(skb)->gso_type;
         struct sw_flow_key later_key;
@@ -360,7 +364,7 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
                 if (gso_type & SKB_GSO_UDP && skb != segs)
                         key = &later_key;
 
-                err = queue_userspace_packet(dp, skb, key, upcall_info);
+                err = queue_userspace_packet(dp, skb, key, upcall_info, cutlen);
                 if (err)
                         break;
 
@@ -416,7 +420,8 @@ static void pad_packet(struct datapath *dp, struct sk_buff *skb)
 
 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;
@@ -461,7 +466,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
         else
                 hlen = skb->len;
 
-        len = upcall_msg_size(upcall_info, hlen);
+        len = upcall_msg_size(upcall_info, hlen - cutlen);
         user_skb = genlmsg_new(len, GFP_ATOMIC);
         if (!user_skb) {
                 err = -ENOMEM;
@@ -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;
 
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index 427e39a045cf..ab85c1cae255 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -100,11 +100,13 @@ struct datapath {
  * @input_vport: The original vport packet came in on. This value is cached
  * when a packet is received by OVS.
  * @mru: The maximum received fragement size; 0 if the packet is not
+ * @cutlen: The number of bytes from the packet end to be removed.
  * fragmented.
  */
 struct ovs_skb_cb {
         struct vport            *input_vport;
         u16                     mru;
+        u32                     cutlen;
 };
 #define OVS_CB(skb) ((struct ovs_skb_cb *)(skb)->cb)
 
@@ -194,7 +196,8 @@ extern struct genl_family dp_vport_genl_family;
 void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key);
 void ovs_dp_detach_port(struct vport *);
 int ovs_dp_upcall(struct datapath *, struct sk_buff *,
-                  const struct sw_flow_key *, const struct dp_upcall_info *);
+                  const struct sw_flow_key *, const struct dp_upcall_info *,
+                  uint32_t cutlen);
 
 const char *ovs_dp_name(const struct datapath *dp);
 struct sk_buff *ovs_vport_cmd_build_info(struct vport *, u32 pid, u32 seq,
diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 0bb650f4f219..c78a6a1476fb 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -2229,6 +2229,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
                         [OVS_ACTION_ATTR_SAMPLE] = (u32)-1,
                         [OVS_ACTION_ATTR_HASH] = sizeof(struct ovs_action_hash),
                         [OVS_ACTION_ATTR_CT] = (u32)-1,
+                        [OVS_ACTION_ATTR_TRUNC] = sizeof(struct ovs_action_trunc),
                 };
                 const struct ovs_action_push_vlan *vlan;
                 int type = nla_type(a);
@@ -2255,6 +2256,14 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
                                 return -EINVAL;
                         break;
 
+                case OVS_ACTION_ATTR_TRUNC: {
+                        const struct ovs_action_trunc *trunc = nla_data(a);
+
+                        if (trunc->max_len < ETH_HLEN)
+                                return -EINVAL;
+                        break;
+                }
+
                 case OVS_ACTION_ATTR_HASH: {
                         const struct ovs_action_hash *act_hash = nla_data(a);
 
diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 31cbc8c5c7db..6b21fd068d87 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -444,6 +444,7 @@ int ovs_vport_receive(struct vport *vport, struct sk_buff *skb,
 
         OVS_CB(skb)->input_vport = vport;
         OVS_CB(skb)->mru = 0;
+        OVS_CB(skb)->cutlen = 0;
         if (unlikely(dev_net(skb->dev) != ovs_dp_get_net(vport->dp))) {
                 u32 mark;