Re: [patch 26/26] Xen-paravirt_ops: Add the Xen virtual network device driver.

Stephen Hemminger
2007-03-02T00:43:37Z

On Thu, 01 Mar 2007 15:25:09 -0800
Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> The network device frontend driver allows the kernel to access network
> devices exported exported by a virtual machine containing a physical
> network device driver.
>
> Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
> Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
> Cc: netdev@vger.kernel.org
> Cc: Jeff Garzik <jeff@garzik.org>
>
> ---
> drivers/net/Kconfig | 12
> drivers/net/Makefile | 2
> drivers/net/xen-netfront.c | 2066 ++++++++++++++++++++++++++++++++++++++++++++
> include/xen/events.h | 2
> 4 files changed, 2082 insertions(+)
>
> ===================================================================
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -2525,6 +2525,18 @@ source "drivers/atm/Kconfig"
>
> source "drivers/s390/net/Kconfig"
>
> +config XEN_NETDEV_FRONTEND
> + tristate "Xen network device frontend driver"
> + depends on XEN
> + default y
> + help
> + The network device frontend driver allows the kernel to
> + access network devices exported exported by a virtual
> + machine containing a physical network device driver. The
> + frontend driver is intended for unprivileged guest domains;
> + if you are compiling a kernel for a Xen guest, you almost
> + certainly want to enable this.
> +
> config ISERIES_VETH
> tristate "iSeries Virtual Ethernet driver support"
> depends on PPC_ISERIES

Might make more sense earlier in list (near other virtual devices).
===================================================================
>
> +/*
> + * Mutually-exclusive module options to select receive data path:
> + * rx_copy : Packets are copied by network backend into local memory
> + * rx_flip : Page containing packet data is transferred to our ownership
> + * For fully-virtualised guests there is no option - copying must be used.
> + * For paravirtualised guests, flipping is the default.
> + */
> +#ifdef CONFIG_XEN

Hey I thought this driver depended on CONFIG_XEN already?

> +static int MODPARM_rx_copy = 0;
> +module_param_named(rx_copy, MODPARM_rx_copy, bool, 0);
> +MODULE_PARM_DESC(rx_copy, "Copy packets from network card (rather than flip)");
> +static int MODPARM_rx_flip = 0;
> +module_param_named(rx_flip, MODPARM_rx_flip, bool, 0);
> +MODULE_PARM_DESC(rx_flip, "Flip packets from network card (rather than copy)");
> +#else
> +static const int MODPARM_rx_copy = 1;
> +static const int MODPARM_rx_flip = 0;
> +#endif

No MIXED case variable names please.

Why have two mutually exclusive values instead of just one value
with three states: 0 = normal, 1 = copy, 2 = flip?

> +#define DPRINTK(fmt, args...) \
> + pr_debug("netfront (%s:%d) " fmt, \
> + __FUNCTION__, __LINE__, ##args)
> +#define IPRINTK(fmt, args...) \
> + printk(KERN_INFO "netfront: " fmt, ##args)
> +#define WPRINTK(fmt, args...) \
> + printk(KERN_WARNING "netfront: " fmt, ##args)

Could you use dev_dbg, dev_info, dev_warn instead of these macros?

> +
> +/** Send a packet on a net device to encourage switches to learn the
> + * MAC. We send a fake ARP request.
> + *
> + * @param dev device
> + * @return 0 on success, error code otherwise
> + */
Why the sudden urge to use docbook format on one internal function.

> +static int send_fake_arp(struct net_device *dev)
> +{
> + struct sk_buff *skb;
> + u32 src_ip, dst_ip;
> +
> + dst_ip = INADDR_BROADCAST;
> + src_ip = inet_select_addr(dev, dst_ip, RT_SCOPE_LINK);
> +
> + /* No IP? Then nothing to do. */
> + if (src_ip == 0)
> + return 0;
> +
> + skb = arp_create(ARPOP_REPLY, ETH_P_ARP,
> + dst_ip, dev, src_ip,
> + /*dst_hw*/ NULL, /*src_hw*/ NULL,
> + /*target_hw*/ dev->dev_addr);
> + if (skb == NULL)
> + return -ENOMEM;
> +
> + return dev_queue_xmit(skb);
> +}

This should probably be done in generic (non driver code).
It creates lots of dependencies here.

> +/*
> + * We use this notifier to send out a fake ARP reply to reset switches and
> + * router ARP caches when an IP interface is brought up on a VIF.
> + */
> +static int
> +inetdev_notify(struct notifier_block *this, unsigned long event, void *ptr)
> +{
> + struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
> + struct net_device *dev = ifa->ifa_dev->dev;
> +
> + /* UP event and is it one of our devices? */
> + if (event == NETDEV_UP && dev->open == network_open)
> + (void)send_fake_arp(dev);
> +
> + return NOTIFY_DONE;
> +}

Shouldn't just be a global kernel option for gratuitous ARP.
Doesn't seem to be unique to this driver.
With sysctl to enable it.

--
Stephen Hemminger <shemminger@linux-foundation.org>