[PATCH v2 3/3] tun: Set num_buffers for virtio 1.0

Akihiko Odaki
2025-01-09T06:59:22Z

The specification says the device MUST set num_buffers to 1 if
VIRTIO_NET_F_MRG_RXBUF has not been negotiated.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
drivers/net/tap.c | 2 +-
drivers/net/tun.c | 6 ++++--
drivers/net/tun_vnet.c | 14 +++++++++-----
drivers/net/tun_vnet.h | 4 ++--
4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 60804855510b..fe9554ee5b8b 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -713,7 +713,7 @@ static ssize_t tap_put_user(struct tap_queue *q,
int total;

if (q->flags & IFF_VNET_HDR) {
- struct virtio_net_hdr vnet_hdr;
+ struct virtio_net_hdr_v1 vnet_hdr;

vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index dbf0dee92e93..f211d0580887 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1991,7 +1991,9 @@ static ssize_t tun_put_user_xdp(struct tun_struct *tun,
size_t total;

if (tun->flags & IFF_VNET_HDR) {
- struct virtio_net_hdr gso = { 0 };
+ struct virtio_net_hdr_v1 gso = {
+ .num_buffers = __virtio16_to_cpu(true, 1)
+ };

vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso);
@@ -2044,7 +2046,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
}

if (vnet_hdr_sz) {
- struct virtio_net_hdr gso;
+ struct virtio_net_hdr_v1 gso;

ret = tun_vnet_hdr_from_skb(tun->flags, tun->dev, skb, &gso);
if (ret < 0)
diff --git a/drivers/net/tun_vnet.c b/drivers/net/tun_vnet.c
index ffb2186facd3..a7a7989fae56 100644
--- a/drivers/net/tun_vnet.c
+++ b/drivers/net/tun_vnet.c
@@ -130,15 +130,17 @@ int tun_vnet_hdr_get(int sz, unsigned int flags, struct iov_iter *from,
EXPORT_SYMBOL_GPL(tun_vnet_hdr_get);

int tun_vnet_hdr_put(int sz, struct iov_iter *iter,
- const struct virtio_net_hdr *hdr)
+ const struct virtio_net_hdr_v1 *hdr)
{
+ int content_sz = MIN(sizeof(*hdr), sz);
+
if (iov_iter_count(iter) < sz)
return -EINVAL;

- if (copy_to_iter(hdr, sizeof(*hdr), iter) != sizeof(*hdr))
+ if (copy_to_iter(hdr, content_sz, iter) != content_sz)
return -EFAULT;

- if (iov_iter_zero(sz - sizeof(*hdr), iter) != sz - sizeof(*hdr))
+ if (iov_iter_zero(sz - content_sz, iter) != sz - content_sz)
return -EFAULT;

return 0;
@@ -154,11 +156,11 @@ EXPORT_SYMBOL_GPL(tun_vnet_hdr_to_skb);

int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev,
const struct sk_buff *skb,
- struct virtio_net_hdr *hdr)
+ struct virtio_net_hdr_v1 *hdr)
{
int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0;

- if (virtio_net_hdr_from_skb(skb, hdr,
+ if (virtio_net_hdr_from_skb(skb, (struct virtio_net_hdr *)hdr,
tun_vnet_is_little_endian(flags), true,
vlan_hlen)) {
struct skb_shared_info *sinfo = skb_shinfo(skb);
@@ -176,6 +178,8 @@ int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev,
return -EINVAL;
}

+ hdr->num_buffers = 1;
+
return 0;
}
EXPORT_SYMBOL_GPL(tun_vnet_hdr_from_skb);
diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h
index 2dfdbe92bb24..d8fd94094227 100644
--- a/drivers/net/tun_vnet.h
+++ b/drivers/net/tun_vnet.h
@@ -12,13 +12,13 @@ int tun_vnet_hdr_get(int sz, unsigned int flags, struct iov_iter *from,
struct virtio_net_hdr *hdr);

int tun_vnet_hdr_put(int sz, struct iov_iter *iter,
- const struct virtio_net_hdr *hdr);
+ const struct virtio_net_hdr_v1 *hdr);

int tun_vnet_hdr_to_skb(unsigned int flags, struct sk_buff *skb,
const struct virtio_net_hdr *hdr);

int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev,
const struct sk_buff *skb,
- struct virtio_net_hdr *hdr);
+ struct virtio_net_hdr_v1 *hdr);

#endif /* TUN_VNET_H */

--
2.47.1