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Tsirkin" Cc: Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko , Stephen Hemminger , gur.stavi@huawei.com, devel@daynix.com References: <20250109-tun-v2-0-388d7d5a287a@daynix.com> <20250109-tun-v2-3-388d7d5a287a@daynix.com> <20250109023144-mutt-send-email-mst@kernel.org> <20250109023829-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <20250109023829-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/01/09 16:40, Michael S. Tsirkin wrote: > On Thu, Jan 09, 2025 at 02:32:25AM -0500, Michael S. Tsirkin wrote: >> On Thu, Jan 09, 2025 at 03:58:45PM +0900, Akihiko Odaki wrote: >>> 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 >> >> >> How do we know this is v1 and not v0? Confused. > > Ah I got it, you assume userspace will over-write it > if VIRTIO_NET_F_MRG_RXBUF is set. > If we are leaving this up to userspace, why not let it do > it always? tun may be used with vhost_net, which does not set the field. > >>> --- >>> 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 >