linux-kernel - [PATCH 3/3] tun: Set num

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Message-Id: <20250108-tun-v1-3-67d784b34374@daynix.com>
Date: Wed, 08 Jan 2025 20:40:13 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Jonathan Corbet <corbet@....net>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Jason Wang <jasowang@...hat.com>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Shuah Khan <shuah@...nel.org>, 
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
 netdev@...r.kernel.org, kvm@...r.kernel.org, 
 virtualization@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org, 
 Yuri Benditovich <yuri.benditovich@...nix.com>, 
 Andrew Melnychenko <andrew@...nix.com>, 
 Stephen Hemminger <stephen@...workplumber.org>, gur.stavi@...wei.com, 
 devel@...nix.com, Akihiko Odaki <akihiko.odaki@...nix.com>
Subject: [PATCH 3/3] tun: Set num_buffers for virtio 1.0

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@...nix.com>
---
 drivers/net/tap.c      |  2 +-
 drivers/net/tun.c      |  4 ++--
 drivers/net/tun_vnet.c | 14 +++++++++-----
 drivers/net/tun_vnet.h |  4 ++--
 4 files changed, 14 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..ec6f4ae655fb 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1991,7 +1991,7 @@ 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 = 1 };
 
 		vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
 		ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso);
@@ -2044,7 +2044,7 @@ 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