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macvtap: add GSO/csum offload support
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Added flags field to macvtap_queue to enable/disable processing of
virtio_net_hdr via IFF_VNET_HDR. This flag is checked to prepend virtio_net_hdr
in the receive path and process/skip virtio_net_hdr in the send path.

Original patch by Sridhar, further changes by Arnd.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Arnd Bergmann authored and David S. Miller committed Feb 18, 2010
1 parent 501c774 commit b9fb9ee
Showing 1 changed file with 182 additions and 24 deletions.
206 changes: 182 additions & 24 deletions drivers/net/macvtap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#include <net/net_namespace.h>
#include <net/rtnetlink.h>
#include <net/sock.h>
#include <linux/virtio_net.h>

/*
* A macvtap queue is the central object of this driver, it connects
Expand All @@ -37,6 +38,7 @@ struct macvtap_queue {
struct socket sock;
struct macvlan_dev *vlan;
struct file *file;
unsigned int flags;
};

static struct proto macvtap_proto = {
Expand Down Expand Up @@ -276,6 +278,7 @@ static int macvtap_open(struct inode *inode, struct file *file)
q->sock.ops = &macvtap_socket_ops;
sock_init_data(&q->sock, &q->sk);
q->sk.sk_write_space = macvtap_sock_write_space;
q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;

err = macvtap_set_queue(dev, file, q);
if (err)
Expand Down Expand Up @@ -318,6 +321,111 @@ static unsigned int macvtap_poll(struct file *file, poll_table * wait)
return mask;
}

static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
size_t len, size_t linear,
int noblock, int *err)
{
struct sk_buff *skb;

/* Under a page? Don't bother with paged skb. */
if (prepad + len < PAGE_SIZE || !linear)
linear = len;

skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
err);
if (!skb)
return NULL;

skb_reserve(skb, prepad);
skb_put(skb, linear);
skb->data_len = len - linear;
skb->len += len - linear;

return skb;
}

/*
* macvtap_skb_from_vnet_hdr and macvtap_skb_to_vnet_hdr should
* be shared with the tun/tap driver.
*/
static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
struct virtio_net_hdr *vnet_hdr)
{
unsigned short gso_type = 0;
if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
switch (vnet_hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
case VIRTIO_NET_HDR_GSO_TCPV4:
gso_type = SKB_GSO_TCPV4;
break;
case VIRTIO_NET_HDR_GSO_TCPV6:
gso_type = SKB_GSO_TCPV6;
break;
case VIRTIO_NET_HDR_GSO_UDP:
gso_type = SKB_GSO_UDP;
break;
default:
return -EINVAL;
}

if (vnet_hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
gso_type |= SKB_GSO_TCP_ECN;

if (vnet_hdr->gso_size == 0)
return -EINVAL;
}

if (vnet_hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
if (!skb_partial_csum_set(skb, vnet_hdr->csum_start,
vnet_hdr->csum_offset))
return -EINVAL;
}

if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
skb_shinfo(skb)->gso_size = vnet_hdr->gso_size;
skb_shinfo(skb)->gso_type = gso_type;

/* Header must be checked, and gso_segs computed. */
skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
skb_shinfo(skb)->gso_segs = 0;
}
return 0;
}

static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
struct virtio_net_hdr *vnet_hdr)
{
memset(vnet_hdr, 0, sizeof(*vnet_hdr));

if (skb_is_gso(skb)) {
struct skb_shared_info *sinfo = skb_shinfo(skb);

/* This is a hint as to how much should be linear. */
vnet_hdr->hdr_len = skb_headlen(skb);
vnet_hdr->gso_size = sinfo->gso_size;
if (sinfo->gso_type & SKB_GSO_TCPV4)
vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
else if (sinfo->gso_type & SKB_GSO_TCPV6)
vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
else if (sinfo->gso_type & SKB_GSO_UDP)
vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
else
BUG();
if (sinfo->gso_type & SKB_GSO_TCP_ECN)
vnet_hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
} else
vnet_hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;

if (skb->ip_summed == CHECKSUM_PARTIAL) {
vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
vnet_hdr->csum_start = skb->csum_start -
skb_headroom(skb);
vnet_hdr->csum_offset = skb->csum_offset;
} /* else everything is zero */

return 0;
}


/* Get packet from user space buffer */
static ssize_t macvtap_get_user(struct macvtap_queue *q,
const struct iovec *iv, size_t count,
Expand All @@ -327,22 +435,53 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q,
struct macvlan_dev *vlan;
size_t len = count;
int err;
struct virtio_net_hdr vnet_hdr = { 0 };
int vnet_hdr_len = 0;

if (q->flags & IFF_VNET_HDR) {
vnet_hdr_len = sizeof(vnet_hdr);

err = -EINVAL;
if ((len -= vnet_hdr_len) < 0)
goto err;

err = memcpy_fromiovecend((void *)&vnet_hdr, iv, 0,
vnet_hdr_len);
if (err < 0)
goto err;
if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
vnet_hdr.csum_start + vnet_hdr.csum_offset + 2 >
vnet_hdr.hdr_len)
vnet_hdr.hdr_len = vnet_hdr.csum_start +
vnet_hdr.csum_offset + 2;
err = -EINVAL;
if (vnet_hdr.hdr_len > len)
goto err;
}

err = -EINVAL;
if (unlikely(len < ETH_HLEN))
return -EINVAL;
goto err;

skb = sock_alloc_send_skb(&q->sk, NET_IP_ALIGN + len, noblock, &err);
skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, len, vnet_hdr.hdr_len,
noblock, &err);
if (!skb)
goto err;

skb_reserve(skb, NET_IP_ALIGN);
skb_put(skb, count);

err = skb_copy_datagram_from_iovec(skb, 0, iv, 0, len);
err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len, len);
if (err)
goto err;
goto err_kfree;

skb_set_network_header(skb, ETH_HLEN);
skb_reset_mac_header(skb);
skb->protocol = eth_hdr(skb)->h_proto;

if (vnet_hdr_len) {
err = macvtap_skb_from_vnet_hdr(skb, &vnet_hdr);
if (err)
goto err_kfree;
}

rcu_read_lock_bh();
vlan = rcu_dereference(q->vlan);
if (vlan)
Expand All @@ -353,15 +492,16 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q,

return count;

err_kfree:
kfree_skb(skb);

err:
rcu_read_lock_bh();
vlan = rcu_dereference(q->vlan);
if (vlan)
macvlan_count_rx(q->vlan, 0, false, false);
netdev_get_tx_queue(vlan->dev, 0)->tx_dropped++;
rcu_read_unlock_bh();

kfree_skb(skb);

return err;
}

Expand All @@ -384,18 +524,33 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
{
struct macvlan_dev *vlan;
int ret;
int vnet_hdr_len = 0;

if (q->flags & IFF_VNET_HDR) {
struct virtio_net_hdr vnet_hdr;
vnet_hdr_len = sizeof (vnet_hdr);
if ((len -= vnet_hdr_len) < 0)
return -EINVAL;

ret = macvtap_skb_to_vnet_hdr(skb, &vnet_hdr);
if (ret)
return ret;

if (memcpy_toiovecend(iv, (void *)&vnet_hdr, 0, vnet_hdr_len))
return -EFAULT;
}

len = min_t(int, skb->len, len);

ret = skb_copy_datagram_const_iovec(skb, 0, iv, 0, len);
ret = skb_copy_datagram_const_iovec(skb, 0, iv, vnet_hdr_len, len);

rcu_read_lock_bh();
vlan = rcu_dereference(q->vlan);
if (vlan)
macvlan_count_rx(vlan, len, ret == 0, 0);
rcu_read_unlock_bh();

return ret ? ret : len;
return ret ? ret : (len + vnet_hdr_len);
}

static ssize_t macvtap_do_read(struct macvtap_queue *q, struct kiocb *iocb,
Expand Down Expand Up @@ -473,9 +628,14 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
/* ignore the name, just look at flags */
if (get_user(u, &ifr->ifr_flags))
return -EFAULT;
if (u != (IFF_TAP | IFF_NO_PI))
return -EINVAL;
return 0;

ret = 0;
if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP))
ret = -EINVAL;
else
q->flags = u;

return ret;

case TUNGETIFF:
rcu_read_lock_bh();
Expand All @@ -489,13 +649,13 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,

ret = 0;
if (copy_to_user(&ifr->ifr_name, q->vlan->dev->name, IFNAMSIZ) ||
put_user((TUN_TAP_DEV | TUN_NO_PI), &ifr->ifr_flags))
put_user(q->flags, &ifr->ifr_flags))
ret = -EFAULT;
dev_put(vlan->dev);
return ret;

case TUNGETFEATURES:
if (put_user((IFF_TAP | IFF_NO_PI), up))
if (put_user(IFF_TAP | IFF_NO_PI | IFF_VNET_HDR, up))
return -EFAULT;
return 0;

Expand All @@ -509,15 +669,13 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
case TUNSETOFFLOAD:
/* let the user check for future flags */
if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
TUN_F_TSO_ECN | TUN_F_UFO))
return -EINVAL;

/* TODO: add support for these, so far we don't
support any offload */
if (arg & (TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
TUN_F_TSO_ECN | TUN_F_UFO))
TUN_F_TSO_ECN | TUN_F_UFO))
return -EINVAL;

/* TODO: only accept frames with the features that
got enabled for forwarded frames */
if (!(q->flags & IFF_VNET_HDR))
return -EINVAL;
return 0;

default:
Expand Down

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