Re: [RFC 2/3] vsockmon: Add vsockmon device

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Sat, May 28, 2016 at 06:29:06PM +0200, ggarcia@abra.uab.cat wrote:
> From: Gerard Garcia <ggarcia@deic.uab.cat>
> 
> Signed-off-by: Gerard Garcia <ggarcia@deic.uab.cat>
> ---
>  drivers/net/Kconfig           |   8 ++
>  drivers/net/Makefile          |   1 +
>  drivers/net/vsockmon.c        | 171 ++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/Kbuild     |   1 +
>  include/uapi/linux/vsockmon.h |  37 +++++++++
>  5 files changed, 218 insertions(+)
>  create mode 100644 drivers/net/vsockmon.c
>  create mode 100644 include/uapi/linux/vsockmon.h
> 
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index 0c5415b..42c43b6 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -330,6 +330,14 @@ config NET_VRF
>  	  This option enables the support for mapping interfaces into VRF's. The
>  	  support enables VRF devices.
>  
> +config VSOCKMON
> +    tristate "Virtual vsock monitoring device"
> +    depends on VHOST_VSOCK
> +    ---help---
> +     This option enables a monitoring net device for vsock sockets. It is
> +     mostly intended for developers or support to debug vsock issues. If
> +     unsure, say N.
> +
>  endif # NET_CORE
>  
>  config SUNGEM_PHY
> diff --git a/drivers/net/Makefile b/drivers/net/Makefile
> index 7336cbd..e2188d4 100644
> --- a/drivers/net/Makefile
> +++ b/drivers/net/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_GENEVE) += geneve.o
>  obj-$(CONFIG_GTP) += gtp.o
>  obj-$(CONFIG_NLMON) += nlmon.o
>  obj-$(CONFIG_NET_VRF) += vrf.o
> +obj-$(CONFIG_VSOCKMON) += vsockmon.o
>  
>  #
>  # Networking Drivers
> diff --git a/drivers/net/vsockmon.c b/drivers/net/vsockmon.c
> new file mode 100644
> index 0000000..becddc9
> --- /dev/null
> +++ b/drivers/net/vsockmon.c
> @@ -0,0 +1,171 @@
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/if_arp.h>
> +#include <net/rtnetlink.h>
> +#include <net/sock.h>
> +#include <net/af_vsock.h>
> +#include <uapi/linux/vsockmon.h>
> +
> +/* Virtio transport max packet size plus header */
> +#define DEFAULT_MTU 1024 * 64 + sizeof(struct af_vsockmon_hdr);
> +
> +struct pcpu_lstats {
> +	u64 rx_packets;
> +	u64 rx_bytes;
> +	struct u64_stats_sync syncp;
> +};
> +
> +static int vsockmon_dev_init(struct net_device *dev)
> +{
> +	dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
> +	return dev->lstats == NULL ? -ENOMEM : 0;
> +}
> +
> +static void vsockmon_dev_uninit(struct net_device *dev)
> +{
> +	free_percpu(dev->lstats);
> +}
> +
> +struct vsockmon {
> +	struct vsock_tap vt;
> +};
> +
> +static int vsockmon_open(struct net_device *dev)
> +{
> +	struct vsockmon *vsockmon = netdev_priv(dev);
> +
> +	vsockmon->vt.dev = dev;
> +	vsockmon->vt.module = THIS_MODULE;
> +	return vsock_add_tap(&vsockmon->vt);
> +}
> +
> +static int vsockmon_close(struct net_device *dev) {
> +	struct vsockmon *vsockmon = netdev_priv(dev);
> +
> +	return vsock_remove_tap(&vsockmon->vt);
> +}
> +
> +static netdev_tx_t vsockmon_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> +	int len = skb->len;
> +	struct pcpu_lstats *stats = this_cpu_ptr(dev->lstats);
> +
> +	u64_stats_update_begin(&stats->syncp);
> +	stats->rx_bytes += len;
> +	stats->rx_packets++;
> +	u64_stats_update_end(&stats->syncp);
> +
> +	dev_kfree_skb(skb);
> +
> +	return NETDEV_TX_OK;
> +}
> +
> +static struct rtnl_link_stats64 *
> +vsockmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
> +{
> +	int i;
> +	u64 bytes = 0, packets = 0;
> +
> +	for_each_possible_cpu(i) {
> +		const struct pcpu_lstats *vstats;
> +		u64 tbytes, tpackets;
> +		unsigned int start;
> +
> +		vstats = per_cpu_ptr(dev->lstats, i);
> +
> +		do {
> +			start = u64_stats_fetch_begin_irq(&vstats->syncp);
> +			tbytes = vstats->rx_bytes;
> +			tpackets = vstats->rx_packets;
> +		} while (u64_stats_fetch_retry_irq(&vstats->syncp, start));
> +
> +		packets += tpackets;
> +		bytes += tbytes;
> +	}
> +
> +	stats->rx_packets = packets;
> +	stats->tx_packets = 0;
> +
> +	stats->rx_bytes = bytes;
> +	stats->tx_bytes = 0;
> +
> +	return stats;
> +}
> +
> +static int vsockmon_is_valid_mtu(int new_mtu)
> +{
> +	return new_mtu >= (int) sizeof(struct af_vsockmon_hdr);
> +}
> +
> +static int vsockmon_change_mtu(struct net_device *dev, int new_mtu)
> +{
> +	if (!vsockmon_is_valid_mtu(new_mtu))
> +		return -EINVAL;
> +
> +	dev->mtu = new_mtu;
> +	return 0;
> +}

I wonder if the mtu serves any purpose.  What happens when you change it
from the default value?

> +
> +static const struct net_device_ops vsockmon_ops = {
> +	.ndo_init = vsockmon_dev_init,
> +	.ndo_uninit = vsockmon_dev_uninit,
> +	.ndo_open = vsockmon_open,
> +	.ndo_stop = vsockmon_close,
> +	.ndo_start_xmit = vsockmon_xmit,
> +	.ndo_get_stats64 = vsockmon_get_stats64,
> +	.ndo_change_mtu = vsockmon_change_mtu,
> +};
> +
> +static u32 always_on(struct net_device *dev)
> +{
> +	return 1;
> +}
> +
> +static const struct ethtool_ops vsockmon_ethtool_ops = {
> +	.get_link = always_on,
> +};
> +
> +static void vsockmon_setup(struct net_device *dev)
> +{
> +	dev->type = ARPHRD_VSOCKMON;
> +	dev->priv_flags |= IFF_NO_QUEUE;
> +
> +	dev->netdev_ops	= &vsockmon_ops;
> +	dev->ethtool_ops = &vsockmon_ethtool_ops;
> +	dev->destructor	= free_netdev;
> +
> +	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST |
> +			NETIF_F_HIGHDMA | NETIF_F_LLTX;
> +
> +	dev->flags = IFF_NOARP;
> +
> +	dev->mtu = DEFAULT_MTU;
> +}
> +
> +static struct rtnl_link_ops vsockmon_link_ops __read_mostly = {
> +	.kind			= "vsockmon",
> +	.priv_size		= sizeof(struct vsockmon),
> +	.setup			= vsockmon_setup,
> +};
> +
> +static __init int vsockmon_register(void)
> +{
> +	int ret = rtnl_link_register(&vsockmon_link_ops);
> +	if (!ret)
> +		vsock_init_tap();
> +
> +	return ret;
> +}
> +
> +static __exit void vsockmon_unregister(void)
> +{
> +	rtnl_link_unregister(&vsockmon_link_ops);
> +}
> +
> +module_init(vsockmon_register);
> +module_exit(vsockmon_unregister);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Gerard Garcia <ggarcia@deic.uab.cat>");
> +MODULE_DESCRIPTION("Vsock monitoring device");
> +MODULE_ALIAS_RTNL_LINK("vsockmon");

there should be some mention that this is derived from nlmon.c.

> diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
> index 5f047d2..b1836cc 100644
> --- a/include/uapi/linux/Kbuild
> +++ b/include/uapi/linux/Kbuild
> @@ -454,6 +454,7 @@ header-y += virtio_scsi.h
>  header-y += virtio_types.h
>  header-y += virtio_vsock.h
>  header-y += vm_sockets.h
> +header-y += vsockmon.h
>  header-y += vt.h
>  header-y += wait.h
>  header-y += wanrouter.h
> diff --git a/include/uapi/linux/vsockmon.h b/include/uapi/linux/vsockmon.h
> new file mode 100644
> index 0000000..c73166f
> --- /dev/null
> +++ b/include/uapi/linux/vsockmon.h
> @@ -0,0 +1,37 @@
> +#ifndef _UAPI_VSOCKMON_H
> +#define _UAPI_VSOCKMON_H
> +
> +#include <linux/virtio_vsock.h>
> +
> +/* Packet structure of packets received from the vsockmon device. */
> +
> +struct af_vsockmon_g {
> +	unsigned short op; /* enum af_vsock_g_ops */
> +	unsigned int src_cid;
> +	unsigned int src_port;
> +	unsigned int dst_cid;
> +	unsigned int dst_port;
> +};
> +
> +struct af_vsockmon_hdr {
> +	unsigned short type;  /* enum af_vosck_type */
> +	struct af_vsockmon_g g_hdr;
> +	union {
> +		struct virtio_vsock_hdr virtio_hdr;
> +	} t_hdr;
> +};

How does endianness work?  virtio_hdr uses little-endian fields on the
wire.  I guess that af_vsockmon_g is always CPU-endian.

> +
> +enum af_vsockmon_type {
> +	AF_VSOCK_GENERIC = 1, /* No transport header */
> +	AF_VSOCK_VIRTIO = 2,  /* Addtional virtio transport header */
> +};
> +
> +enum af_vsockmon_g_ops {
> +	AF_VSOCK_G_OP_UNKNOWN = 0,
> +	AF_VSOCK_G_OP_CONNECT = 1,
> +	AF_VSOCK_G_OP_DISCONNECT = 2,
> +	AF_VSOCK_G_OP_CONTROL = 3,
> +	AF_VSOCK_G_OP_PAYLOAD = 4,
> +};
> +
> +#endif
> -- 
> 2.8.3
> 

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