datapath: Make it possible to query vports by name regardless of datapath.
[sliver-openvswitch.git] / datapath / datapath.c
index 2eaead3..3f108c0 100644 (file)
@@ -41,6 +41,7 @@
 #include <linux/rculist.h>
 #include <linux/dmi.h>
 #include <net/inet_ecn.h>
+#include <net/genetlink.h>
 #include <linux/compat.h>
 
 #include "openvswitch/datapath-protocol.h"
@@ -491,7 +492,7 @@ void dp_process_received_packet(struct vport *p, struct sk_buff *skb)
        OVS_CB(skb)->vport = p;
 
        if (!OVS_CB(skb)->flow) {
-               struct odp_flow_key key;
+               struct sw_flow_key key;
                struct tbl_node *flow_node;
                bool is_frag;
 
@@ -512,8 +513,15 @@ void dp_process_received_packet(struct vport *p, struct sk_buff *skb)
                flow_node = tbl_lookup(rcu_dereference(dp->table), &key,
                                        flow_hash(&key), flow_cmp);
                if (unlikely(!flow_node)) {
-                       dp_output_control(dp, skb, _ODPL_MISS_NR,
-                                        (__force u64)OVS_CB(skb)->tun_id);
+                       struct dp_upcall_info upcall;
+
+                       upcall.type = _ODPL_MISS_NR;
+                       upcall.key = &key;
+                       upcall.userdata = 0;
+                       upcall.sample_pool = 0;
+                       upcall.actions = NULL;
+                       upcall.actions_len = 0;
+                       dp_upcall(dp, skb, &upcall);
                        stats_counter_off = offsetof(struct dp_stats_percpu, n_missed);
                        goto out;
                }
@@ -562,10 +570,26 @@ out:
        local_bh_enable();
 }
 
+static void copy_and_csum_skb(struct sk_buff *skb, void *to)
+{
+       u16 csum_start, csum_offset;
+       __wsum csum;
+
+       get_skb_csum_pointers(skb, &csum_start, &csum_offset);
+       csum_start -= skb_headroom(skb);
+       BUG_ON(csum_start >= skb_headlen(skb));
+
+       skb_copy_bits(skb, 0, to, csum_start);
+
+       csum = skb_copy_and_csum_bits(skb, csum_start, to + csum_start,
+                                     skb->len - csum_start, 0);
+       *(__sum16 *)(to + csum_start + csum_offset) = csum_fold(csum);
+}
+
 /* Append each packet in 'skb' list to 'queue'.  There will be only one packet
  * unless we broke up a GSO packet. */
-static int queue_control_packets(struct sk_buff *skb, struct sk_buff_head *queue,
-                                int queue_no, u64 arg)
+static int queue_control_packets(struct datapath *dp, struct sk_buff *skb,
+                                const struct dp_upcall_info *upcall_info)
 {
        struct sk_buff *nskb;
        int port_no;
@@ -577,22 +601,61 @@ static int queue_control_packets(struct sk_buff *skb, struct sk_buff_head *queue
                port_no = ODPP_LOCAL;
 
        do {
-               struct odp_msg *header;
+               struct odp_packet *upcall;
+               struct sk_buff *user_skb; /* to be queued to userspace */
+               struct nlattr *nla;
+               unsigned int len;
 
                nskb = skb->next;
                skb->next = NULL;
 
-               err = skb_cow(skb, sizeof(*header));
-               if (err)
+               len = sizeof(struct odp_packet);
+               len += nla_total_size(4); /* ODP_PACKET_ATTR_TYPE. */
+               len += nla_total_size(skb->len);
+               len += nla_total_size(FLOW_BUFSIZE);
+               if (upcall_info->userdata)
+                       len += nla_total_size(8);
+               if (upcall_info->sample_pool)
+                       len += nla_total_size(4);
+               if (upcall_info->actions_len)
+                       len += nla_total_size(upcall_info->actions_len);
+
+               user_skb = alloc_skb(len, GFP_ATOMIC);
+               if (!user_skb)
                        goto err_kfree_skbs;
 
-               header = (struct odp_msg*)__skb_push(skb, sizeof(*header));
-               header->type = queue_no;
-               header->length = skb->len;
-               header->port = port_no;
-               header->arg = arg;
-               skb_queue_tail(queue, skb);
+               upcall = (struct odp_packet *)__skb_put(user_skb, sizeof(*upcall));
+               upcall->dp_idx = dp->dp_idx;
+
+               nla_put_u32(user_skb, ODP_PACKET_ATTR_TYPE, upcall_info->type);
+
+               nla = nla_nest_start(user_skb, ODP_PACKET_ATTR_KEY);
+               flow_to_nlattrs(upcall_info->key, user_skb);
+               nla_nest_end(user_skb, nla);
 
+               if (upcall_info->userdata)
+                       nla_put_u64(user_skb, ODP_PACKET_ATTR_USERDATA, upcall_info->userdata);
+               if (upcall_info->sample_pool)
+                       nla_put_u32(user_skb, ODP_PACKET_ATTR_SAMPLE_POOL, upcall_info->sample_pool);
+               if (upcall_info->actions_len) {
+                       const struct nlattr *actions = upcall_info->actions;
+                       u32 actions_len = upcall_info->actions_len;
+
+                       nla = nla_nest_start(user_skb, ODP_PACKET_ATTR_ACTIONS);
+                       memcpy(__skb_put(user_skb, actions_len), actions, actions_len);
+                       nla_nest_end(user_skb, nla);
+               }
+
+               nla = __nla_reserve(user_skb, ODP_PACKET_ATTR_PACKET, skb->len);
+               if (skb->ip_summed == CHECKSUM_PARTIAL)
+                       copy_and_csum_skb(skb, nla_data(nla));
+               else
+                       skb_copy_bits(skb, 0, nla_data(nla), skb->len);
+
+               upcall->len = user_skb->len;
+               skb_queue_tail(&dp->queues[upcall_info->type], user_skb);
+
+               kfree_skb(skb);
                skb = nskb;
        } while (skb);
        return 0;
@@ -606,16 +669,16 @@ err_kfree_skbs:
        return err;
 }
 
-int dp_output_control(struct datapath *dp, struct sk_buff *skb, int queue_no,
-                     u64 arg)
+int dp_upcall(struct datapath *dp, struct sk_buff *skb, const struct dp_upcall_info *upcall_info)
 {
        struct dp_stats_percpu *stats;
        struct sk_buff_head *queue;
        int err;
 
        WARN_ON_ONCE(skb_shared(skb));
-       BUG_ON(queue_no != _ODPL_MISS_NR && queue_no != _ODPL_ACTION_NR && queue_no != _ODPL_SFLOW_NR);
-       queue = &dp->queues[queue_no];
+       BUG_ON(upcall_info->type >= DP_N_QUEUES);
+
+       queue = &dp->queues[upcall_info->type];
        err = -ENOBUFS;
        if (skb_queue_len(queue) >= DP_MAX_QUEUE_LEN)
                goto err_kfree_skb;
@@ -639,7 +702,7 @@ int dp_output_control(struct datapath *dp, struct sk_buff *skb, int queue_no,
                }
        }
 
-       err = queue_control_packets(skb, queue, queue_no, arg);
+       err = queue_control_packets(dp, skb, upcall_info);
        wake_up_interruptible(&dp->waitqueue);
        return err;
 
@@ -825,15 +888,21 @@ static int do_put_flow(struct datapath *dp, struct odp_flow_put *uf,
                       struct odp_flow_stats *stats)
 {
        struct tbl_node *flow_node;
+       struct sw_flow_key key;
        struct sw_flow *flow;
        struct tbl *table;
        struct sw_flow_actions *acts = NULL;
        int error;
        u32 hash;
 
-       hash = flow_hash(&uf->flow.key);
+       error = flow_copy_from_user(&key, (const struct nlattr __force __user *)uf->flow.key,
+                                   uf->flow.key_len);
+       if (error)
+               return error;
+
+       hash = flow_hash(&key);
        table = get_table_protected(dp);
-       flow_node = tbl_lookup(table, &uf->flow.key, hash, flow_cmp);
+       flow_node = tbl_lookup(table, &key, hash, flow_cmp);
        if (!flow_node) {
                /* No such flow. */
                error = -ENOENT;
@@ -854,7 +923,7 @@ static int do_put_flow(struct datapath *dp, struct odp_flow_put *uf,
                        error = PTR_ERR(flow);
                        goto error;
                }
-               flow->key = uf->flow.key;
+               flow->key = key;
                clear_stats(flow);
 
                /* Obtain actions. */
@@ -983,13 +1052,18 @@ static int answer_query(struct datapath *dp, struct sw_flow *flow,
                               &ufp->stats, actions, &ufp->actions_len);
 }
 
-static struct sw_flow *do_del_flow(struct datapath *dp, struct odp_flow_key *key)
+static struct sw_flow *do_del_flow(struct datapath *dp, const struct nlattr __user *key, u32 key_len)
 {
        struct tbl *table = get_table_protected(dp);
        struct tbl_node *flow_node;
+       struct sw_flow_key swkey;
        int error;
 
-       flow_node = tbl_lookup(table, key, flow_hash(key), flow_cmp);
+       error = flow_copy_from_user(&swkey, key, key_len);
+       if (error)
+               return ERR_PTR(error);
+
+       flow_node = tbl_lookup(table, &swkey, flow_hash(&swkey), flow_cmp);
        if (!flow_node)
                return ERR_PTR(-ENOENT);
 
@@ -1013,7 +1087,7 @@ static int del_flow(struct datapath *dp, struct odp_flow __user *ufp)
        if (copy_from_user(&uf, ufp, sizeof(uf)))
                return -EFAULT;
 
-       flow = do_del_flow(dp, &uf.key);
+       flow = do_del_flow(dp, (const struct nlattr __force __user *)uf.key, uf.key_len);
        if (IS_ERR(flow))
                return PTR_ERR(flow);
 
@@ -1029,6 +1103,7 @@ static int do_query_flows(struct datapath *dp, const struct odp_flowvec *flowvec
 
        for (i = 0; i < flowvec->n_flows; i++) {
                struct odp_flow __user *ufp = (struct odp_flow __user __force *)&flowvec->flows[i];
+               struct sw_flow_key key;
                struct odp_flow uf;
                struct tbl_node *flow_node;
                int error;
@@ -1036,7 +1111,11 @@ static int do_query_flows(struct datapath *dp, const struct odp_flowvec *flowvec
                if (copy_from_user(&uf, ufp, sizeof(uf)))
                        return -EFAULT;
 
-               flow_node = tbl_lookup(table, &uf.key, flow_hash(&uf.key), flow_cmp);
+               error = flow_copy_from_user(&key, (const struct nlattr __force __user *)uf.key, uf.key_len);
+               if (error)
+                       return error;
+
+               flow_node = tbl_lookup(table, &uf.key, flow_hash(&key), flow_cmp);
                if (!flow_node)
                        error = put_user(ENOENT, &ufp->stats.error);
                else
@@ -1088,7 +1167,9 @@ static struct sw_flow *do_dump_flow(struct datapath *dp, u32 __user *state)
 static int dump_flow(struct datapath *dp, struct odp_flow_dump __user *udumpp)
 {
        struct odp_flow __user *uflowp;
+       struct nlattr __user *ukey;
        struct sw_flow *flow;
+       u32 key_len;
 
        flow = do_dump_flow(dp, udumpp->state);
        if (IS_ERR(flow))
@@ -1100,15 +1181,23 @@ static int dump_flow(struct datapath *dp, struct odp_flow_dump __user *udumpp)
        if (!flow)
                return put_user(ODPFF_EOF, &uflowp->flags);
 
-       if (copy_to_user(&uflowp->key, &flow->key, sizeof(struct odp_flow_key)) ||
-           put_user(0, &uflowp->flags))
+       if (put_user(0, &uflowp->flags) ||
+           get_user(ukey, (struct nlattr __user * __user*)&uflowp->key) ||
+           get_user(key_len, &uflowp->key_len))
+               return -EFAULT;
+
+       key_len = flow_copy_to_user(ukey, &flow->key, key_len);
+       if (key_len < 0)
+               return key_len;
+       if (put_user(key_len, &uflowp->key_len))
                return -EFAULT;
+
        return answer_query(dp, flow, 0, uflowp);
 }
 
 static int do_execute(struct datapath *dp, const struct odp_execute *execute)
 {
-       struct odp_flow_key key;
+       struct sw_flow_key key;
        struct sk_buff *skb;
        struct sw_flow_actions *actions;
        struct ethhdr *eth;
@@ -1260,85 +1349,85 @@ void set_internal_devs_mtu(const struct datapath *dp)
        }
 }
 
-static int put_port(const struct vport *p, struct odp_port __user *uop)
+static void compose_odp_port(const struct vport *vport, struct odp_port *odp_port)
 {
-       struct odp_port op;
-
-       memset(&op, 0, sizeof(op));
-
        rcu_read_lock();
-       strncpy(op.devname, vport_get_name(p), sizeof(op.devname));
-       strncpy(op.type, vport_get_type(p), sizeof(op.type));
-       vport_get_config(p, op.config);
+       strncpy(odp_port->devname, vport_get_name(vport), sizeof(odp_port->devname));
+       strncpy(odp_port->type, vport_get_type(vport), sizeof(odp_port->type));
+       vport_get_config(vport, odp_port->config);
+       odp_port->port = vport->port_no;
+       odp_port->dp_idx = vport->dp->dp_idx;
        rcu_read_unlock();
-
-       op.port = p->port_no;
-
-       return copy_to_user(uop, &op, sizeof(op)) ? -EFAULT : 0;
 }
 
-static int query_port(struct datapath *dp, struct odp_port __user *uport)
+static int query_port(int dp_idx, struct odp_port __user *uport)
 {
        struct odp_port port;
-       struct vport *vport;
 
        if (copy_from_user(&port, uport, sizeof(port)))
                return -EFAULT;
 
        if (port.devname[0]) {
+               struct vport *vport;
+
                port.devname[IFNAMSIZ - 1] = '\0';
 
                vport_lock();
                vport = vport_locate(port.devname);
+               if (vport)
+                       compose_odp_port(vport, &port);
                vport_unlock();
 
                if (!vport)
                        return -ENODEV;
-               if (vport->dp != dp)
-                       return -ENOENT;
        } else {
+               struct vport *vport;
+               struct datapath *dp;
+
                if (port.port >= DP_MAX_PORTS)
                        return -EINVAL;
 
+               dp = get_dp_locked(dp_idx);
+               if (!dp)
+                       return -ENODEV;
+
                vport = get_vport_protected(dp, port.port);
+               if (vport)
+                       compose_odp_port(vport, &port);
+               mutex_unlock(&dp->mutex);
+
                if (!vport)
                        return -ENOENT;
        }
 
-       return put_port(vport, uport);
+       return copy_to_user(uport, &port, sizeof(struct odp_port));
 }
 
-static int do_list_ports(struct datapath *dp, struct odp_port __user *uports,
-                        int n_ports)
+static int do_dump_port(struct datapath *dp, struct odp_vport_dump *dump)
 {
-       int idx = 0;
-       if (n_ports) {
-               struct vport *p;
-
-               list_for_each_entry_rcu (p, &dp->port_list, node) {
-                       if (put_port(p, &uports[idx]))
-                               return -EFAULT;
-                       if (idx++ >= n_ports)
-                               break;
+       u32 port_no;
+
+       for (port_no = dump->port_no; port_no < DP_MAX_PORTS; port_no++) {
+               struct vport *vport = get_vport_protected(dp, port_no);
+               if (vport) {
+                       struct odp_port odp_port;
+
+                       compose_odp_port(vport, &odp_port);
+                       return copy_to_user((struct odp_port __force __user*)dump->port, &odp_port, sizeof(struct odp_port));
                }
        }
-       return idx;
+
+       return put_user('\0', (char __force __user*)&dump->port->devname[0]);
 }
 
-static int list_ports(struct datapath *dp, struct odp_portvec __user *upv)
+static int dump_port(struct datapath *dp, struct odp_vport_dump __user *udump)
 {
-       struct odp_portvec pv;
-       int retval;
+       struct odp_vport_dump dump;
 
-       if (copy_from_user(&pv, upv, sizeof(pv)))
+       if (copy_from_user(&dump, udump, sizeof(dump)))
                return -EFAULT;
 
-       retval = do_list_ports(dp, (struct odp_port __user __force *)pv.ports,
-                              pv.n_ports);
-       if (retval < 0)
-               return retval;
-
-       return put_user(retval, &upv->n_ports);
+       return do_dump_port(dp, &dump);
 }
 
 static int get_listen_mask(const struct file *f)
@@ -1380,6 +1469,10 @@ static long openvswitch_ioctl(struct file *f, unsigned int cmd,
                        err = detach_port(dp_idx, port_no);
                goto exit;
 
+       case ODP_VPORT_QUERY:
+               err = query_port(dp_idx, (struct odp_port __user *)argp);
+               goto exit;
+
        case ODP_VPORT_MOD:
                err = vport_user_mod((struct odp_port __user *)argp);
                goto exit;
@@ -1459,12 +1552,8 @@ static long openvswitch_ioctl(struct file *f, unsigned int cmd,
                        dp->sflow_probability = sflow_probability;
                break;
 
-       case ODP_VPORT_QUERY:
-               err = query_port(dp, (struct odp_port __user *)argp);
-               break;
-
-       case ODP_VPORT_LIST:
-               err = list_ports(dp, (struct odp_portvec __user *)argp);
+       case ODP_VPORT_DUMP:
+               err = dump_port(dp, (struct odp_vport_dump __user *)argp);
                break;
 
        case ODP_FLOW_FLUSH:
@@ -1511,33 +1600,34 @@ static int dp_has_packet_of_interest(struct datapath *dp, int listeners)
 }
 
 #ifdef CONFIG_COMPAT
-static int compat_list_ports(struct datapath *dp, struct compat_odp_portvec __user *upv)
+static int compat_dump_port(struct datapath *dp, struct compat_odp_vport_dump __user *compat)
 {
-       struct compat_odp_portvec pv;
-       int retval;
+       struct odp_vport_dump dump;
+       compat_uptr_t port;
 
-       if (copy_from_user(&pv, upv, sizeof(pv)))
+       if (!access_ok(VERIFY_READ, compat, sizeof(struct compat_odp_vport_dump)) ||
+           __get_user(port, &compat->port) ||
+           __get_user(dump.port_no, &compat->port_no))
                return -EFAULT;
 
-       retval = do_list_ports(dp, compat_ptr(pv.ports), pv.n_ports);
-       if (retval < 0)
-               return retval;
-
-       return put_user(retval, &upv->n_ports);
+       dump.port = (struct odp_port __force *)compat_ptr(port);
+       return do_dump_port(dp, &dump);
 }
 
 static int compat_get_flow(struct odp_flow *flow, const struct compat_odp_flow __user *compat)
 {
-       compat_uptr_t actions;
+       compat_uptr_t key, actions;
 
        if (!access_ok(VERIFY_READ, compat, sizeof(struct compat_odp_flow)) ||
            __copy_from_user(&flow->stats, &compat->stats, sizeof(struct odp_flow_stats)) ||
-           __copy_from_user(&flow->key, &compat->key, sizeof(struct odp_flow_key)) ||
+           __get_user(key, &compat->key) ||
+           __get_user(flow->key_len, &compat->key_len) ||
            __get_user(actions, &compat->actions) ||
            __get_user(flow->actions_len, &compat->actions_len) ||
            __get_user(flow->flags, &compat->flags))
                return -EFAULT;
 
+       flow->key = (struct nlattr __force *)compat_ptr(key);
        flow->actions = (struct nlattr __force *)compat_ptr(actions);
        return 0;
 }
@@ -1585,7 +1675,7 @@ static int compat_del_flow(struct datapath *dp, struct compat_odp_flow __user *u
        if (compat_get_flow(&uf, ufp))
                return -EFAULT;
 
-       flow = do_del_flow(dp, &uf.key);
+       flow = do_del_flow(dp, (const struct nlattr __force __user *)uf.key, uf.key_len);
        if (IS_ERR(flow))
                return PTR_ERR(flow);
 
@@ -1605,12 +1695,17 @@ static int compat_query_flows(struct datapath *dp,
                struct compat_odp_flow __user *ufp = &flows[i];
                struct odp_flow uf;
                struct tbl_node *flow_node;
+               struct sw_flow_key key;
                int error;
 
                if (compat_get_flow(&uf, ufp))
                        return -EFAULT;
 
-               flow_node = tbl_lookup(table, &uf.key, flow_hash(&uf.key), flow_cmp);
+               error = flow_copy_from_user(&key, (const struct nlattr __force __user *) uf.key, uf.key_len);
+               if (error)
+                       return error;
+
+               flow_node = tbl_lookup(table, &key, flow_hash(&key), flow_cmp);
                if (!flow_node)
                        error = put_user(ENOENT, &ufp->stats.error);
                else
@@ -1627,6 +1722,8 @@ static int compat_dump_flow(struct datapath *dp, struct compat_odp_flow_dump __u
        struct compat_odp_flow __user *uflowp;
        compat_uptr_t compat_ufp;
        struct sw_flow *flow;
+       compat_uptr_t ukey;
+       u32 key_len;
 
        flow = do_dump_flow(dp, udumpp->state);
        if (IS_ERR(flow))
@@ -1639,9 +1736,17 @@ static int compat_dump_flow(struct datapath *dp, struct compat_odp_flow_dump __u
        if (!flow)
                return put_user(ODPFF_EOF, &uflowp->flags);
 
-       if (copy_to_user(&uflowp->key, &flow->key, sizeof(struct odp_flow_key)) ||
-           put_user(0, &uflowp->flags))
+       if (put_user(0, &uflowp->flags) ||
+           get_user(ukey, &uflowp->key) ||
+           get_user(key_len, &uflowp->key_len))
+               return -EFAULT;
+
+       key_len = flow_copy_to_user(compat_ptr(ukey), &flow->key, key_len);
+       if (key_len < 0)
+               return key_len;
+       if (put_user(key_len, &uflowp->key_len))
                return -EFAULT;
+
        return compat_answer_query(dp, flow, 0, uflowp);
 }
 
@@ -1733,8 +1838,8 @@ static long openvswitch_compat_ioctl(struct file *f, unsigned int cmd, unsigned
                goto exit;
 
        switch (cmd) {
-       case ODP_VPORT_LIST32:
-               err = compat_list_ports(dp, compat_ptr(argp));
+       case ODP_VPORT_DUMP32:
+               err = compat_dump_port(dp, compat_ptr(argp));
                break;
 
        case ODP_FLOW_PUT32:
@@ -1767,100 +1872,6 @@ exit:
 }
 #endif
 
-/* Unfortunately this function is not exported so this is a verbatim copy
- * from net/core/datagram.c in 2.6.30. */
-static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
-                                     u8 __user *to, int len,
-                                     __wsum *csump)
-{
-       int start = skb_headlen(skb);
-       int pos = 0;
-       int i, copy = start - offset;
-
-       /* Copy header. */
-       if (copy > 0) {
-               int err = 0;
-               if (copy > len)
-                       copy = len;
-               *csump = csum_and_copy_to_user(skb->data + offset, to, copy,
-                                              *csump, &err);
-               if (err)
-                       goto fault;
-               if ((len -= copy) == 0)
-                       return 0;
-               offset += copy;
-               to += copy;
-               pos = copy;
-       }
-
-       for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
-               int end;
-
-               WARN_ON(start > offset + len);
-
-               end = start + skb_shinfo(skb)->frags[i].size;
-               if ((copy = end - offset) > 0) {
-                       __wsum csum2;
-                       int err = 0;
-                       u8  *vaddr;
-                       skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
-                       struct page *page = frag->page;
-
-                       if (copy > len)
-                               copy = len;
-                       vaddr = kmap(page);
-                       csum2 = csum_and_copy_to_user(vaddr +
-                                                       frag->page_offset +
-                                                       offset - start,
-                                                     to, copy, 0, &err);
-                       kunmap(page);
-                       if (err)
-                               goto fault;
-                       *csump = csum_block_add(*csump, csum2, pos);
-                       if (!(len -= copy))
-                               return 0;
-                       offset += copy;
-                       to += copy;
-                       pos += copy;
-               }
-               start = end;
-       }
-
-       if (skb_shinfo(skb)->frag_list) {
-               struct sk_buff *list = skb_shinfo(skb)->frag_list;
-
-               for (; list; list=list->next) {
-                       int end;
-
-                       WARN_ON(start > offset + len);
-
-                       end = start + list->len;
-                       if ((copy = end - offset) > 0) {
-                               __wsum csum2 = 0;
-                               if (copy > len)
-                                       copy = len;
-                               if (skb_copy_and_csum_datagram(list,
-                                                              offset - start,
-                                                              to, copy,
-                                                              &csum2))
-                                       goto fault;
-                               *csump = csum_block_add(*csump, csum2, pos);
-                               if ((len -= copy) == 0)
-                                       return 0;
-                               offset += copy;
-                               to += copy;
-                               pos += copy;
-                       }
-                       start = end;
-               }
-       }
-       if (!len)
-               return 0;
-
-fault:
-       return -EFAULT;
-}
-
 static ssize_t openvswitch_read(struct file *f, char __user *buf,
                                size_t nbytes, loff_t *ppos)
 {
@@ -1868,7 +1879,7 @@ static ssize_t openvswitch_read(struct file *f, char __user *buf,
        int dp_idx = iminor(f->f_dentry->d_inode);
        struct datapath *dp = get_dp_locked(dp_idx);
        struct sk_buff *skb;
-       size_t copy_bytes, tot_copy_bytes;
+       struct iovec iov;
        int retval;
 
        if (!dp)
@@ -1905,44 +1916,11 @@ static ssize_t openvswitch_read(struct file *f, char __user *buf,
 success:
        mutex_unlock(&dp->mutex);
 
-       copy_bytes = tot_copy_bytes = min_t(size_t, skb->len, nbytes);
-
-       retval = 0;
-       if (skb->ip_summed == CHECKSUM_PARTIAL) {
-               if (copy_bytes == skb->len) {
-                       __wsum csum = 0;
-                       u16 csum_start, csum_offset;
-
-                       get_skb_csum_pointers(skb, &csum_start, &csum_offset);
-                       csum_start -= skb_headroom(skb);
-
-                       BUG_ON(csum_start >= skb_headlen(skb));
-                       retval = skb_copy_and_csum_datagram(skb, csum_start, buf + csum_start,
-                                                           copy_bytes - csum_start, &csum);
-                       if (!retval) {
-                               __sum16 __user *csump;
-
-                               copy_bytes = csum_start;
-                               csump = (__sum16 __user *)(buf + csum_start + csum_offset);
-
-                               BUG_ON((char __user *)csump + sizeof(__sum16) >
-                                       buf + nbytes);
-                               put_user(csum_fold(csum), csump);
-                       }
-               } else
-                       retval = skb_checksum_help(skb);
-       }
-
-       if (!retval) {
-               struct iovec iov;
-
-               iov.iov_base = buf;
-               iov.iov_len = copy_bytes;
-               retval = skb_copy_datagram_iovec(skb, 0, &iov, iov.iov_len);
-       }
-
+       iov.iov_base = buf;
+       iov.iov_len = min_t(size_t, skb->len, nbytes);
+       retval = skb_copy_datagram_iovec(skb, 0, &iov, iov.iov_len);
        if (!retval)
-               retval = tot_copy_bytes;
+               retval = skb->len;
 
        kfree_skb(skb);
        return retval;