Subject: Re: [PATCH net-next v2 6/9] net: use core MTU range checking in virt drivers

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 20 Oct 2016 23:23:54 +0300

On Thu, Oct 20, 2016 at 01:55:21PM -0400, Jarod Wilson wrote:
> hyperv_net:
> - set min/max_mtu, per Haiyang, after rndis_filter_device_add
> 
> virtio_net:
> - set min/max_mtu
> - remove virtnet_change_mtu
> vmxnet3:
> - set min/max_mtu
> 
> xen-netback:
> - min_mtu = 0, max_mtu = 65517
> 
> xen-netfront:
> - min_mtu = 0, max_mtu = 65535
> 
> unisys/visor:
> - clean up defines a little to not clash with network core or add
>   redundat definitions
> 
> CC: [email-masked]
> CC: [email-masked]
> CC: "K. Y. Srinivasan" <[email-masked]>
> CC: Haiyang Zhang <[email-masked]>
> CC: "Michael S. Tsirkin" <[email-masked]>
> CC: Shrikrishna Khare <[email-masked]>
> CC: "VMware, Inc." <[email-masked]>
> CC: Wei Liu <[email-masked]>
> CC: Paul Durrant <[email-masked]>
> CC: David Kershner <[email-masked]>
> Signed-off-by: Jarod Wilson <[email-masked]>
> ---
>  drivers/net/hyperv/hyperv_net.h                 |  4 ++--
>  drivers/net/hyperv/netvsc_drv.c                 | 14 +++++++-------
>  drivers/net/virtio_net.c                        | 23 ++++++++++-------------
>  drivers/net/vmxnet3/vmxnet3_drv.c               |  7 ++++---
>  drivers/net/xen-netback/interface.c             |  5 ++++-
>  drivers/net/xen-netfront.c                      |  2 ++
>  drivers/staging/unisys/include/iochannel.h      | 10 ++++------
>  drivers/staging/unisys/visornic/visornic_main.c |  4 ++--
>  8 files changed, 35 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index f4fbcb5..3958ada 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -606,8 +606,8 @@ struct nvsp_message {
>  } __packed;
>  
>  
> -#define NETVSC_MTU 65536
> -#define NETVSC_MTU_MIN 68
> +#define NETVSC_MTU 65535
> +#define NETVSC_MTU_MIN ETH_MIN_MTU
>  
>  #define NETVSC_RECEIVE_BUFFER_SIZE		(1024*1024*16)	/* 16MB */
>  #define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY	(1024*1024*15)  /* 15MB */
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index f0919bd..3b28cf1 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -872,19 +872,12 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
>  	struct netvsc_device *nvdev = ndevctx->nvdev;
>  	struct hv_device *hdev = ndevctx->device_ctx;
>  	struct netvsc_device_info device_info;
> -	int limit = ETH_DATA_LEN;
>  	u32 num_chn;
>  	int ret = 0;
>  
>  	if (ndevctx->start_remove || !nvdev || nvdev->destroy)
>  		return -ENODEV;
>  
> -	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
> -		limit = NETVSC_MTU - ETH_HLEN;
> -
> -	if (mtu < NETVSC_MTU_MIN || mtu > limit)
> -		return -EINVAL;
> -
>  	ret = netvsc_close(ndev);
>  	if (ret)
>  		goto out;
> @@ -1402,6 +1395,13 @@ static int netvsc_probe(struct hv_device *dev,
>  	netif_set_real_num_tx_queues(net, nvdev->num_chn);
>  	netif_set_real_num_rx_queues(net, nvdev->num_chn);
>  
> +	/* MTU range: 68 - 1500 or 65521 */
> +	net->min_mtu = NETVSC_MTU_MIN;
> +	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
> +		net->max_mtu = NETVSC_MTU - ETH_HLEN;
> +	else
> +		net->max_mtu = ETH_DATA_LEN;
> +
>  	ret = register_netdev(net);
>  	if (ret != 0) {
>  		pr_err("Unable to register netdev.\n");
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index fad84f3..720809f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1419,17 +1419,6 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
>  	.set_settings = virtnet_set_settings,
>  };
>  
> -#define MIN_MTU 68
> -#define MAX_MTU 65535
> -
> -static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
> -{
> -	if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
> -		return -EINVAL;
> -	dev->mtu = new_mtu;
> -	return 0;
> -}
> -
>  static const struct net_device_ops virtnet_netdev = {
>  	.ndo_open            = virtnet_open,
>  	.ndo_stop   	     = virtnet_close,
> @@ -1437,7 +1426,6 @@ static const struct net_device_ops virtnet_netdev = {
>  	.ndo_validate_addr   = eth_validate_addr,
>  	.ndo_set_mac_address = virtnet_set_mac_address,
>  	.ndo_set_rx_mode     = virtnet_set_rx_mode,
> -	.ndo_change_mtu	     = virtnet_change_mtu,
>  	.ndo_get_stats64     = virtnet_stats,
>  	.ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
>  	.ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
> @@ -1748,6 +1736,9 @@ static bool virtnet_validate_features(struct virtio_device *vdev)
>  	return true;
>  }
>  
> +#define MIN_MTU ETH_MIN_MTU
> +#define MAX_MTU ETH_MAX_MTU
> +

Can we drop these btw?

>  static int virtnet_probe(struct virtio_device *vdev)
>  {
>  	int i, err;
> @@ -1821,6 +1812,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>  
>  	dev->vlan_features = dev->features;
>  
> +	/* MTU range: 68 - 65535 */
> +	dev->min_mtu = MIN_MTU;
> +	dev->max_mtu = MAX_MTU;
> +
>  	/* Configuration may specify what MAC to use.  Otherwise random. */
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
>  		virtio_cread_bytes(vdev,
> @@ -1875,8 +1870,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		mtu = virtio_cread16(vdev,
>  				     offsetof(struct virtio_net_config,
>  					      mtu));
> -		if (virtnet_change_mtu(dev, mtu))
> +		if (mtu < dev->min_mtu || mtu > dev->max_mtu)

In fact the > max_mtu branch does not make sense since a 16 bit
value can't exceed MAX_MTU.

>  			__virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
> +		else
> +			dev->mtu = mtu;
>  	}
>  
>  	if (vi->any_header_sg)
> diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
> index b5554f2..0c36de1 100644
> --- a/drivers/net/vmxnet3/vmxnet3_drv.c
> +++ b/drivers/net/vmxnet3/vmxnet3_drv.c
> @@ -2969,9 +2969,6 @@ vmxnet3_change_mtu(struct net_device *netdev, int new_mtu)
>  	struct vmxnet3_adapter *adapter = netdev_priv(netdev);
>  	int err = 0;
>  
> -	if (new_mtu < VMXNET3_MIN_MTU || new_mtu > VMXNET3_MAX_MTU)
> -		return -EINVAL;
> -
>  	netdev->mtu = new_mtu;
>  
>  	/*
> @@ -3428,6 +3425,10 @@ vmxnet3_probe_device(struct pci_dev *pdev,
>  	vmxnet3_set_ethtool_ops(netdev);
>  	netdev->watchdog_timeo = 5 * HZ;
>  
> +	/* MTU range: 60 - 9000 */
> +	netdev->min_mtu = VMXNET3_MIN_MTU;
> +	netdev->max_mtu = VMXNET3_MAX_MTU;
> +
>  	INIT_WORK(&adapter->work, vmxnet3_reset_work);
>  	set_bit(VMXNET3_STATE_BIT_QUIESCED, &adapter->state);
>  
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 74dc2bf..e30ffd2 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -302,7 +302,7 @@ static int xenvif_close(struct net_device *dev)
>  static int xenvif_change_mtu(struct net_device *dev, int mtu)
>  {
>  	struct xenvif *vif = netdev_priv(dev);
> -	int max = vif->can_sg ? 65535 - VLAN_ETH_HLEN : ETH_DATA_LEN;
> +	int max = vif->can_sg ? ETH_MAX_MTU - VLAN_ETH_HLEN : ETH_DATA_LEN;
>  
>  	if (mtu > max)
>  		return -EINVAL;
> @@ -471,6 +471,9 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
>  
>  	dev->tx_queue_len = XENVIF_QUEUE_LENGTH;
>  
> +	dev->min_mtu = 0;
> +	dev->max_mtu = ETH_MAX_MTU - VLAN_ETH_HLEN;
> +
>  	/*
>  	 * Initialise a dummy MAC address. We choose the numerically
>  	 * largest non-broadcast address to prevent the address getting
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index e17879d..7d616b0 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -1329,6 +1329,8 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
>  	netdev->features |= netdev->hw_features;
>  
>  	netdev->ethtool_ops = &xennet_ethtool_ops;
> +	netdev->min_mtu = 0;
> +	netdev->max_mtu = XEN_NETIF_MAX_TX_SIZE;
>  	SET_NETDEV_DEV(netdev, &dev->dev);
>  
>  	np->netdev = netdev;
> diff --git a/drivers/staging/unisys/include/iochannel.h b/drivers/staging/unisys/include/iochannel.h
> index cba4433..9081b3f 100644
> --- a/drivers/staging/unisys/include/iochannel.h
> +++ b/drivers/staging/unisys/include/iochannel.h
> @@ -113,12 +113,10 @@ enum net_types {
>  
>  };
>  
> -#define		ETH_HEADER_SIZE 14	/* size of ethernet header */
> -
>  #define		ETH_MIN_DATA_SIZE 46	/* minimum eth data size */
> -#define		ETH_MIN_PACKET_SIZE (ETH_HEADER_SIZE + ETH_MIN_DATA_SIZE)
> +#define		ETH_MIN_PACKET_SIZE (ETH_HLEN + ETH_MIN_DATA_SIZE)
>  
> -#define		ETH_MAX_MTU 16384	/* maximum data size */
> +#define		VISOR_ETH_MAX_MTU 16384	/* maximum data size */
>  
>  #ifndef MAX_MACADDR_LEN
>  #define MAX_MACADDR_LEN 6	/* number of bytes in MAC address */
> @@ -288,7 +286,7 @@ struct net_pkt_xmt {
>  	int len;	/* full length of data in the packet */
>  	int num_frags;	/* number of fragments in frags containing data */
>  	struct phys_info frags[MAX_PHYS_INFO];	/* physical page information */
> -	char ethhdr[ETH_HEADER_SIZE];	/* the ethernet header  */
> +	char ethhdr[ETH_HLEN];	/* the ethernet header  */
>  	struct {
>  		/* these are needed for csum at uisnic end */
>  		u8 valid;	/* 1 = struct is valid - else ignore */
> @@ -323,7 +321,7 @@ struct net_pkt_xmtdone {
>   */
>  #define RCVPOST_BUF_SIZE 4032
>  #define MAX_NET_RCV_CHAIN \
> -	((ETH_MAX_MTU + ETH_HEADER_SIZE + RCVPOST_BUF_SIZE - 1) \
> +	((VISOR_ETH_MAX_MTU + ETH_HLEN + RCVPOST_BUF_SIZE - 1) \
>  	/ RCVPOST_BUF_SIZE)
>  
>  struct net_pkt_rcvpost {
> diff --git a/drivers/staging/unisys/visornic/visornic_main.c b/drivers/staging/unisys/visornic/visornic_main.c
> index 1367007..f8a584b 100644
> --- a/drivers/staging/unisys/visornic/visornic_main.c
> +++ b/drivers/staging/unisys/visornic/visornic_main.c
> @@ -791,7 +791,7 @@ visornic_xmit(struct sk_buff *skb, struct net_device *netdev)
>  	 * pointing to
>  	 */
>  	firstfraglen = skb->len - skb->data_len;
> -	if (firstfraglen < ETH_HEADER_SIZE) {
> +	if (firstfraglen < ETH_HLEN) {
>  		spin_unlock_irqrestore(&devdata->priv_lock, flags);
>  		devdata->busy_cnt++;
>  		dev_err(&netdev->dev,
> @@ -864,7 +864,7 @@ visornic_xmit(struct sk_buff *skb, struct net_device *netdev)
>  	/* copy ethernet header from first frag into ocmdrsp
>  	 * - everything else will be pass in frags & DMA'ed
>  	 */
> -	memcpy(cmdrsp->net.xmt.ethhdr, skb->data, ETH_HEADER_SIZE);
> +	memcpy(cmdrsp->net.xmt.ethhdr, skb->data, ETH_HLEN);
>  	/* copy frags info - from skb->data we need to only provide access
>  	 * beyond eth header
>  	 */
> -- 
> 2.10.0