Re: [PATCH v3 1/3] VSOCK: Add vsockmon tap functions

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 12, 2017 at 05:08:23PM +0100, Stefan Hajnoczi wrote:
> From: Gerard Garcia <ggarcia@deic.uab.cat>
> 
> Add tap functions that can be used by the vsock transports to
> deliver packets to vsockmon virtual network devices.
> 
> Signed-off-by: Gerard Garcia <ggarcia@deic.uab.cat>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> v3:
>  * Include missing <linux/module.h> header in af_vsock_tap.c
> ---
>  net/vmw_vsock/Makefile       |   2 +-
>  include/net/af_vsock.h       |  13 +++++
>  include/uapi/linux/if_arp.h  |   1 +
>  net/vmw_vsock/af_vsock_tap.c | 114 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 129 insertions(+), 1 deletion(-)
>  create mode 100644 net/vmw_vsock/af_vsock_tap.c
> 
> diff --git a/net/vmw_vsock/Makefile b/net/vmw_vsock/Makefile
> index bc27c70..09fc2eb 100644
> --- a/net/vmw_vsock/Makefile
> +++ b/net/vmw_vsock/Makefile
> @@ -3,7 +3,7 @@ obj-$(CONFIG_VMWARE_VMCI_VSOCKETS) += vmw_vsock_vmci_transport.o
>  obj-$(CONFIG_VIRTIO_VSOCKETS) += vmw_vsock_virtio_transport.o
>  obj-$(CONFIG_VIRTIO_VSOCKETS_COMMON) += vmw_vsock_virtio_transport_common.o
>  
> -vsock-y += af_vsock.o vsock_addr.o
> +vsock-y += af_vsock.o af_vsock_tap.o vsock_addr.o
>  
>  vmw_vsock_vmci_transport-y += vmci_transport.o vmci_transport_notify.o \
>  	vmci_transport_notify_qstate.o
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index f32ed9a..c526d4f 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -188,4 +188,17 @@ struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
>  void vsock_remove_sock(struct vsock_sock *vsk);
>  void vsock_for_each_connected_socket(void (*fn)(struct sock *sk));
>  
> +/**** TAP ****/
> +
> +struct vsock_tap {
> +	struct net_device *dev;
> +	struct module *module;
> +	struct list_head list;
> +};
> +
> +int vsock_init_tap(void);
> +int vsock_add_tap(struct vsock_tap *vt);
> +int vsock_remove_tap(struct vsock_tap *vt);
> +void vsock_deliver_tap(struct sk_buff *skb);
> +
>  #endif /* __AF_VSOCK_H__ */
> diff --git a/include/uapi/linux/if_arp.h b/include/uapi/linux/if_arp.h
> index 4d024d7..cf73510 100644
> --- a/include/uapi/linux/if_arp.h
> +++ b/include/uapi/linux/if_arp.h
> @@ -95,6 +95,7 @@
>  #define ARPHRD_IP6GRE	823		/* GRE over IPv6		*/
>  #define ARPHRD_NETLINK	824		/* Netlink header		*/
>  #define ARPHRD_6LOWPAN	825		/* IPv6 over LoWPAN             */
> +#define ARPHRD_VSOCKMON	826		/* Vsock monitor header		*/
>  
>  #define ARPHRD_VOID	  0xFFFF	/* Void type, nothing is known */
>  #define ARPHRD_NONE	  0xFFFE	/* zero header length */
> diff --git a/net/vmw_vsock/af_vsock_tap.c b/net/vmw_vsock/af_vsock_tap.c
> new file mode 100644
> index 0000000..db3188e
> --- /dev/null
> +++ b/net/vmw_vsock/af_vsock_tap.c
> @@ -0,0 +1,114 @@
> +/*
> + * Tap functions for AF_VSOCK sockets.
> + *
> + * Code based on net/netlink/af_netlink.c tap functions.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/module.h>
> +#include <net/sock.h>
> +#include <net/af_vsock.h>
> +#include <linux/if_arp.h>
> +
> +static DEFINE_SPINLOCK(vsock_tap_lock);
> +static struct list_head vsock_tap_all __read_mostly =
> +				LIST_HEAD_INIT(vsock_tap_all);
> +
> +int vsock_add_tap(struct vsock_tap *vt) {
> +	if (unlikely(vt->dev->type != ARPHRD_VSOCKMON))
> +		return -EINVAL;
> +
> +	__module_get(vt->module);
> +
> +	spin_lock(&vsock_tap_lock);
> +	list_add_rcu(&vt->list, &vsock_tap_all);
> +	spin_unlock(&vsock_tap_lock);
> +
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(vsock_add_tap);
> +
> +int __vsock_remove_tap(struct vsock_tap *vt) {
> +	bool found = false;
> +	struct vsock_tap *tmp;
> +
> +	spin_lock(&vsock_tap_lock);
> +
> +	list_for_each_entry(tmp, &vsock_tap_all, list) {
> +		if (vt == tmp) {
> +			list_del_rcu(&vt->list);
> +			found = true;
> +			goto out;
> +		}
> +	}
> +
> +	pr_warn("__vsock_remove_tap: %p not found\n", vt);
> +out:
> +	spin_unlock(&vsock_tap_lock);
> +
> +	if (found)
> +		module_put(vt->module);

This is called before synchronize_net so there might
still be users for this tap.

> +
> +	return found ? 0 : -ENODEV;
> +}
> +
> +int vsock_remove_tap(struct vsock_tap *vt)
> +{
> +	int ret;
> +
> +	ret = __vsock_remove_tap(vt);
> +	synchronize_net();
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(vsock_remove_tap);
> +
> +static int __vsock_deliver_tap_skb(struct sk_buff *skb,
> +				     struct net_device *dev)
> +{
> +	int ret = 0;
> +	struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
> +
> +	if (nskb) {
> +		dev_hold(dev);
> +
> +		nskb->dev = dev;
> +		ret = dev_queue_xmit(nskb);
> +		if (unlikely(ret > 0))
> +			ret = net_xmit_errno(ret);
> +
> +		dev_put(dev);
> +	}
> +
> +	return ret;
> +}
> +
> +static void __vsock_deliver_tap(struct sk_buff *skb)
> +{
> +	int ret;
> +	struct vsock_tap *tmp;
> +
> +	list_for_each_entry_rcu(tmp, &vsock_tap_all, list) {
> +		ret = __vsock_deliver_tap_skb(skb, tmp->dev);
> +		if (unlikely(ret))
> +			break;
> +	}
> +
> +	consume_skb(skb);
> +}
> +
> +void vsock_deliver_tap(struct sk_buff *skb)
> +{
> +	rcu_read_lock();
> +
> +	if (unlikely(!list_empty(&vsock_tap_all)))
> +		__vsock_deliver_tap(skb);
> +
> +	rcu_read_unlock();
> +}
> +EXPORT_SYMBOL_GPL(vsock_deliver_tap);
> -- 
> 2.9.3