Subject: Re: [RFC net-next 3/6] net: Introduce VRF device driver - v2

From: Nikolay Aleksandrov <[email-masked]>
Date: Mon, 06 Jul 2015 18:37:53 +0200

On 07/06/2015 05:03 PM, David Ahern wrote:
> This driver borrows heavily from IPvlan and teaming drivers.
> 
> Routing domains (VRF-lite) are created by instantiating a device
> and enslaving all routed interfaces that participate in the domain.
> As part of the enslavement, all local routes pointing to enslaved
> devices are re-pointed to the vrf device, thus forcing outgoing
> sockets to bind to the vrf to function.
> 
> Standard FIB rules can then bind the VRF device to tables and regular
> fib rule processing is followed.
> 
> Routed traffic through the box, is fwded by using the VRF device as
> the IIF and following the IIF rule to a table which is mated with
> the VRF.
> 
> Locally originated traffic is directed at the VRF device using
> SO_BINDTODEVICE or cmsg headers. This in turn drops the packet into
> the xmit function of the vrf driver, which then completes the ip lookup
> and output.
> 
> This solution is completely orthogonal to namespaces and allow the L3
> equivalent of vlans to exist allowing the routing space to be
> partitioned.
> 
> Example:
> 
>    Create vrf 1:
>      ip link add vrf1 type vrf table 5
>      ip rule add iif vrf1 table 5
>      ip rule add oif vrf1 table 5
>      ip route add table 5 prohibit default
>      ip link set vrf1 up
> 
>    Add interface to vrf 1:
>      ip link set eth1 master vrf1
> 
> Signed-off-by: Shrijeet Mukherjee <[email-masked]>
> Signed-off-by: David Ahern <[email-masked]>
> 
> v2:
> - addressed comments from first RFC
> - significant changes to improve simplicity of implementation
> ---
>  drivers/net/Kconfig  |   7 +
>  drivers/net/Makefile |   1 +
>  drivers/net/vrf.c    | 486 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/net/vrf.h    |  71 ++++++++
>  4 files changed, 565 insertions(+)
>  create mode 100644 drivers/net/vrf.c
>  create mode 100644 include/net/vrf.h
> 
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index 019fceffc9e5..b040aa233408 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -283,6 +283,13 @@ config NLMON
>  	  diagnostics, etc. This is mostly intended for developers or support
>  	  to debug netlink issues. If unsure, say N.
>  
> +config NET_VRF
> +	tristate "Virtual Routing and Forwarding (Lite)"
> +	depends on IP_MULTIPLE_TABLES && IPV6_MULTIPLE_TABLES
> +	---help---
> +          This option enables the support for mapping interfaces into VRF's. The
> +          support enables VRF devices
> +
>  endif # NET_CORE
>  
>  config SUNGEM_PHY
> diff --git a/drivers/net/Makefile b/drivers/net/Makefile
> index c12cb22478a7..ca16dd689b36 100644
> --- a/drivers/net/Makefile
> +++ b/drivers/net/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
>  obj-$(CONFIG_VXLAN) += vxlan.o
>  obj-$(CONFIG_GENEVE) += geneve.o
>  obj-$(CONFIG_NLMON) += nlmon.o
> +obj-$(CONFIG_NET_VRF) += vrf.o
>  
>  #
>  # Networking Drivers
> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
> new file mode 100644
> index 000000000000..b9f9ae68388d
> --- /dev/null
> +++ b/drivers/net/vrf.c
> @@ -0,0 +1,487 @@
> +/*
> + * vrf.c: device driver to encapsulate a VRF space
> + *
> + * Copyright (c) 2015 Cumulus Networks
> + *
> + * Based on dummy, team and ipvlan drivers
> + *
> + * 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 <linux/kernel.h>
> +#include <linux/netdevice.h>
> +#include <linux/etherdevice.h>
> +#include <linux/ip.h>
> +#include <linux/init.h>
> +#include <linux/moduleparam.h>
> +#include <linux/rtnetlink.h>
> +#include <net/rtnetlink.h>
> +#include <net/arp.h>
> +#include <linux/u64_stats_sync.h>
> +#include <linux/hashtable.h>
> +
> +#include <linux/inetdevice.h>
> +#include <net/ip.h>
> +#include <net/ip_fib.h>
> +#include <net/ip6_route.h>
> +#include <net/rtnetlink.h>
> +#include <net/route.h>
> +#include <net/addrconf.h>
> +#include <net/vrf.h>
> +
> +#define DRV_NAME	"vrf"
> +#define DRV_VERSION	"1.0"
> +
> +#define vrf_is_slave(dev)   ((dev)->flags & IFF_SLAVE)
> +#define vrf_is_master(dev)  ((dev)->flags & IFF_MASTER)
> +
> +#define vrf_master_get_rcu(dev) \
> +	((struct net_device *)rcu_dereference(dev->rx_handler_data))
> +
> +struct pcpu_dstats {
> +	u64			tx_pkts;
> +	u64			tx_bytes;
> +	u64			tx_drps;
> +	u64			rx_pkts;
> +	u64			rx_bytes;
> +	struct u64_stats_sync	syncp;
> +};
> +
> +struct slave {
> +	struct list_head	list;
> +	struct net_device	*dev;
> +	long			priority;
> +};
> +
> +struct slave_queue {
> +	spinlock_t		lock; /* lock for slave insert/delete */
> +	struct list_head	all_slaves;
> +	int			num_slaves;
> +	struct net_device	*master_dev;
> +};
> +
> +struct net_vrf {
> +	struct slave_queue	queue;
> +	struct fib_table        *tb;
> +	u32                     tb_id;
> +};
> +
> +static int is_ip_rx_frame(struct sk_buff *skb)
> +{
> +	switch (skb->protocol) {
> +	case htons(ETH_P_IP):
> +	case htons(ETH_P_IPV6):
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +/* note: already called with rcu_read_lock */
> +static rx_handler_result_t vrf_handle_frame(struct sk_buff **pskb)
> +{
> +	struct sk_buff *skb = *pskb;
> +
> +	if (is_ip_rx_frame(skb)) {
> +		struct net_device *dev = vrf_master_get_rcu(skb->dev);
> +		struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
> +
> +		u64_stats_update_begin(&dstats->syncp);
> +		dstats->rx_pkts++;
> +		dstats->rx_bytes += skb->len;
> +		u64_stats_update_end(&dstats->syncp);
> +	}
> +	return RX_HANDLER_PASS;
> +}
> +
> +static struct rtnl_link_stats64 *vrf_get_stats64(
> +	struct net_device *dev, struct rtnl_link_stats64 *stats)
> +{
> +	int i;
> +
> +	for_each_possible_cpu(i) {
> +		const struct pcpu_dstats *dstats;
> +		u64 tbytes, tpkts, tdrops, rbytes, rpkts;
> +		unsigned int start;
> +
> +		dstats = per_cpu_ptr(dev->dstats, i);
> +		do {
> +			start = u64_stats_fetch_begin_irq(&dstats->syncp);
> +			tbytes = dstats->tx_bytes;
> +			tpkts = dstats->tx_pkts;
> +			tdrops = dstats->tx_drps;
> +			rbytes = dstats->rx_bytes;
> +			rpkts = dstats->rx_pkts;
> +		} while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
> +		stats->tx_bytes += tbytes;
> +		stats->tx_packets += tpkts;
> +		stats->tx_dropped += tdrops;
> +		stats->rx_bytes += rbytes;
> +		stats->rx_packets += rpkts;
> +	}
> +	return stats;
> +}
> +
> +static netdev_tx_t vrf_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> +	return NET_XMIT_DROP;
> +}
> +
> +/**************************** device handling ********************/
> +
> +/* queue->lock must be held */
> +static struct slave *__vrf_find_slave_dev(struct slave_queue *queue,
> +					  struct net_device *dev)
> +{
> +	struct list_head *this, *head;
> +
> +	head = &queue->all_slaves;
> +	list_for_each(this, head) {
> +		struct slave *slave = list_entry(this, struct slave, list);
> +
> +		if (slave->dev == dev)
> +			return slave;
> +	}
> +
> +	return NULL;
> +}
> +
> +static void __vrf_kill_slave(struct slave_queue *queue, struct slave *slave)
> +{
> +	list_del(&slave->list);
> +	queue->num_slaves--;
> +	slave->dev->flags &= ~IFF_SLAVE;
> +	netdev_rx_handler_unregister(slave->dev);
> +	kfree(slave->dev->vrf_ptr);
> +	slave->dev->vrf_ptr = NULL;
> +	dev_put(slave->dev);
> +	kfree(slave);
> +}
> +
> +/* queue->lock must be held */
> +static void __vrf_insert_slave(struct slave_queue *queue, struct slave *slave,
> +			       struct net_device *master)
> +{
> +	struct slave *duplicate_slave = NULL;
> +
> +	duplicate_slave = __vrf_find_slave_dev(queue, slave->dev);
> +	if (duplicate_slave)
> +		__vrf_kill_slave(queue, duplicate_slave);
> +
> +	dev_hold(slave->dev);
> +	list_add(&slave->list, &queue->all_slaves);
> +	queue->num_slaves++;
> +}
> +
> +/* netlink lock is assumed here */
> +static int vrf_add_slave(struct net_device *dev,
> +			 struct net_device *port_dev)
> +{
> +	if (!dev || !port_dev || dev_net(dev) != dev_net(port_dev))
> +		return -ENODEV;
> +
> +	if (!vrf_is_master(port_dev) && !vrf_is_slave(port_dev)) {
> +		struct slave *s = kzalloc(sizeof(*s), GFP_KERNEL);
> +		struct net_vrf *vrf = netdev_priv(dev);
> +		struct slave_queue *queue = &vrf->queue;
> +		bool is_running = netif_running(port_dev);
> +		unsigned int flags = port_dev->flags;
> +		int ret;
> +
> +		if (!s)
> +			return -ENOMEM;
> +
> +		s->dev = port_dev;
> +
> +		spin_lock_bh(&queue->lock);
> +		__vrf_insert_slave(queue, s, dev);
> +		spin_unlock_bh(&queue->lock);
> +
> +		port_dev->vrf_ptr = kmalloc(sizeof(*port_dev->vrf_ptr),
> +					    GFP_KERNEL);
> +		if (!port_dev->vrf_ptr)
> +			return -ENOMEM;
                        ^^^^^^^^^
I believe you'll have a slave in the list with inconsistent state which could
even lead to null ptr derefernce if vrf_ptr is used, also __vrf_insert_slave
does dev_hold so the dev refcnt will be incorrect as well.

> +
> +		port_dev->vrf_ptr->ifindex = dev->ifindex;
> +		port_dev->vrf_ptr->tb_id = vrf->tb_id;
> +
> +		/* register the packet handler for slave ports */
> +		ret = netdev_rx_handler_register(port_dev, vrf_handle_frame,
> +						 (void *)dev);
> +		if (ret) {
> +			netdev_err(port_dev,
> +				   "Device %s failed to register rx_handler\n",
> +				   port_dev->name);
> +			kfree(port_dev->vrf_ptr);
> +			kfree(s);
> +			return ret;
                        ^^^^^^^^^^
The slave is being freed while on the list here, device's refcnt will be wrong etc.

> +		}
> +
> +		if (is_running) {
> +			ret = dev_change_flags(port_dev, flags & ~IFF_UP);
> +			if (ret < 0)
> +				goto out_fail;
> +		}
> +
> +		ret = netdev_master_upper_dev_link(port_dev, dev);
> +		if (ret < 0)
> +			goto out_fail;
> +
> +		if (is_running) {
> +			ret = dev_change_flags(port_dev, flags);
> +			if (ret < 0)
> +				goto out_fail;
> +		}
> +
> +		port_dev->flags |= IFF_SLAVE;
> +
> +		return 0;
> +
> +out_fail:
> +		spin_lock_bh(&queue->lock);
> +		__vrf_kill_slave(queue, s);
> +		spin_unlock_bh(&queue->lock);

__vrf_kill_slave() doesn't do upper device unlink and the device can be linked
if we fail in the dev_change_flags above.

> +
> +		return ret;
> +	}
> +
> +	return -EINVAL;
> +}
^^^^
In my opinion the structure of the above function should change to something more
straightforward with proper exit labels and cleanup upon failure, also a level of
indentation can be avoided.

> +
> +static int vrf_del_slave(struct net_device *dev,
> +			 struct net_device *port_dev)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +	struct slave_queue *queue = &vrf->queue;
> +	struct slave *slave = __vrf_find_slave_dev(queue, port_dev);
> +	bool is_running = netif_running(port_dev);
> +	unsigned int flags = port_dev->flags;
> +	int ret = 0;

ret seems unused/unchecked in this function

> +
> +	if (!slave)
> +		return -EINVAL;
> +
> +	if (is_running)
> +		ret = dev_change_flags(port_dev, flags & ~IFF_UP);
> +
> +	spin_lock_bh(&queue->lock);
> +	__vrf_kill_slave(queue, slave);
> +	spin_unlock_bh(&queue->lock);
> +
> +	netdev_upper_dev_unlink(port_dev, dev);
> +
> +	if (is_running)
> +		ret = dev_change_flags(port_dev, flags);
> +
> +	return 0;
> +}
> +
> +static int vrf_dev_init(struct net_device *dev)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +
> +	spin_lock_init(&vrf->queue.lock);
> +	INIT_LIST_HEAD(&vrf->queue.all_slaves);
> +	vrf->queue.master_dev = dev;
> +
> +	dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
> +	dev->flags  =  IFF_MASTER | IFF_NOARP;
> +	if (!dev->dstats)
> +		return -ENOMEM;
        ^^^^^
nit: I'd suggest moving the check after the allocation

> +
> +	return 0;
> +}
> +
> +static void vrf_dev_uninit(struct net_device *dev)
> +{
> +	free_percpu(dev->dstats);
> +}
> +
> +static int vrf_dev_close(struct net_device *dev)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +	struct slave_queue *queue = &vrf->queue;
> +	struct list_head *this, *head;
> +
> +	head = &queue->all_slaves;
> +	list_for_each(this, head) {
> +		struct slave *slave = list_entry(this, struct slave, list);
> +
> +		slave->dev->vrf_ptr->ifindex = 0;
> +		slave->dev->vrf_ptr->tb_id = 0;
> +	}
> +
> +	if (dev->flags & IFF_MASTER)
> +		dev->flags &= ~IFF_UP;
> +
> +	return 0;
> +}
> +
> +static int vrf_dev_open(struct net_device *dev)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +	struct slave_queue *queue = &vrf->queue;
> +	struct list_head *this, *head;
> +
> +	head = &queue->all_slaves;
> +	list_for_each(this, head) {
> +		struct slave *slave = list_entry(this, struct slave, list);
> +
> +		slave->dev->vrf_ptr->ifindex = dev->ifindex;
> +		slave->dev->vrf_ptr->tb_id = vrf->tb_id;
> +	}
> +
> +	if (dev->flags & IFF_MASTER)
> +		dev->flags |= IFF_UP;
> +
> +	if (!vrf->tb)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static const struct net_device_ops vrf_netdev_ops = {
> +	.ndo_init		= vrf_dev_init,
> +	.ndo_uninit		= vrf_dev_uninit,
> +	.ndo_open		= vrf_dev_open,
> +	.ndo_stop               = vrf_dev_close,
> +	.ndo_start_xmit		= vrf_xmit,
> +	.ndo_get_stats64	= vrf_get_stats64,
> +	.ndo_add_slave          = vrf_add_slave,
> +	.ndo_del_slave          = vrf_del_slave,
> +};
> +
> +static void vrf_get_drvinfo(struct net_device *dev,
> +			    struct ethtool_drvinfo *info)
> +{
> +	strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
> +	strlcpy(info->version, DRV_VERSION, sizeof(info->version));
> +}
> +
> +static const struct ethtool_ops vrf_ethtool_ops = {
> +	.get_drvinfo            = vrf_get_drvinfo,
> +};
> +
> +static void vrf_setup(struct net_device *dev)
> +{
> +	ether_setup(dev);
> +
> +	/* Initialize the device structure. */
> +	dev->netdev_ops = &vrf_netdev_ops;
> +	dev->ethtool_ops = &vrf_ethtool_ops;
> +	dev->destructor = free_netdev;
> +
> +	/* Fill in device structure with ethernet-generic values. */
> +	dev->tx_queue_len = 0;
> +	eth_hw_addr_random(dev);
> +}
> +
> +static int vrf_validate(struct nlattr *tb[], struct nlattr *data[])
> +{
> +	if (tb[IFLA_ADDRESS]) {
> +		if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
> +			return -EINVAL;
> +		if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
> +			return -EADDRNOTAVAIL;
> +	}
> +	return 0;
> +}
> +
> +static int vrf_newlink(struct net *src_net, struct net_device *dev,
> +		       struct nlattr *tb[], struct nlattr *data[])
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +	int err;
> +
> +	if (!data || !data[IFLA_VRF_TABLE])
> +		return -EINVAL;
> +
> +	vrf->tb_id = nla_get_u32(data[IFLA_VRF_TABLE]);
> +
> +	/* reserve a table for this VRF device */
> +	err = -ERANGE;
> +	vrf->tb = fib_new_table(dev_net(dev), vrf->tb_id);
> +	if (!vrf->tb)
> +		goto out_fail;
> +
> +	dev->priv_flags |= IFF_VRF_MASTER;
> +
> +	err = -ENOMEM;
> +	dev->vrf_ptr = kmalloc(sizeof(*dev->vrf_ptr), GFP_KERNEL);
> +	if (!dev->vrf_ptr)
> +		goto out_fail;
> +
> +	dev->vrf_ptr->ifindex = dev->ifindex;
> +	dev->vrf_ptr->tb_id = vrf->tb_id;
> +
> +	err = register_netdevice(dev);
> +	if (err < 0)
> +		goto out_fail;
> +
> +	return 0;
> +
> +out_fail:
> +	kfree(dev->vrf_ptr);
> +	free_netdev(dev);
> +	return err;
> +}
> +
> +static void vrf_dellink(struct net_device *dev, struct list_head *head)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +
> +	kfree(dev->vrf_ptr);
> +	fib_free_table(vrf->tb);
> +}
> +
> +static size_t vrf_nl_getsize(const struct net_device *dev)
> +{
> +	return nla_total_size(sizeof(u32));  /* IFLA_VRF_TABLE */
> +}
> +
> +static int vrf_fillinfo(struct sk_buff *skb,
> +			const struct net_device *dev)
> +{
> +	struct net_vrf *vrf = netdev_priv(dev);
> +
> +	return nla_put_u32(skb, IFLA_VRF_TABLE, vrf->tb_id);
> +}
> +
> +static const struct nla_policy vrf_nl_policy[IFLA_VRF_MAX + 1] = {
> +	[IFLA_VRF_TABLE] = { .type = NLA_U32 },
> +};
> +
> +static struct rtnl_link_ops vrf_link_ops __read_mostly = {
> +	.kind		= DRV_NAME,
> +	.priv_size      = sizeof(struct net_vrf),
> +
> +	.get_size       = vrf_nl_getsize,
> +	.policy         = vrf_nl_policy,
> +	.validate	= vrf_validate,
> +	.fill_info      = vrf_fillinfo,
> +
> +	.newlink        = vrf_newlink,
> +	.dellink        = vrf_dellink,
> +	.setup		= vrf_setup,
> +	.maxtype        = IFLA_VRF_MAX,
> +};
> +
> +static int __init vrf_init_module(void)
> +{
> +	return rtnl_link_register(&vrf_link_ops);
> +}
> +
> +static void __exit vrf_cleanup_module(void)
> +{
> +	rtnl_link_unregister(&vrf_link_ops);
> +}
> +
> +module_init(vrf_init_module);
> +module_exit(vrf_cleanup_module);
> +MODULE_AUTHOR("Shrijeet Mukherjee, David Ahern");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_RTNL_LINK(DRV_NAME);
> +MODULE_VERSION(DRV_VERSION);
> diff --git a/include/net/vrf.h b/include/net/vrf.h
> new file mode 100644
> index 000000000000..3ab1e332c781
> --- /dev/null
> +++ b/include/net/vrf.h
> @@ -0,0 +1,71 @@
> +/*
> + * include/net/net_vrf.h - adds vrf dev structure definitions
> + * Copyright (c) 2015 Cumulus Networks
> + *
> + * 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.
> + */
> +
> +#ifndef __LINUX_NET_VRF_H
> +#define __LINUX_NET_VRF_H
> +
> +struct net_vrf_dev {
> +	int                     ifindex; /* ifindex of master dev */
> +	u32                     tb_id;   /* table id for VRF */
> +};
> +
> +#if IS_ENABLED(CONFIG_NET_VRF)
> +static inline int vrf_master_dev_idx(const struct net_device *dev)
> +{
> +	int idx = 0;
> +
> +	if (dev && dev->vrf_ptr)
> +		idx = dev->vrf_ptr->ifindex;
> +
> +	return idx;
> +}
> +
> +static inline int vrf_get_master_dev_idx(struct net *net, int idx)
> +{
> +	int rc = 0;
> +
> +	if (idx) {
> +		struct net_device *dev = dev_get_by_index(net, idx);
> +
> +		if (dev) {
> +			rc = vrf_master_dev_idx(dev);
> +			dev_put(dev);
> +		}
> +	}
> +	return rc;
> +}
> +
> +static inline int vrf_dev_table(const struct net_device *dev)
> +{
> +	int tb_id = 0;
> +
> +	if (dev && dev->vrf_ptr)
> +		tb_id = dev->vrf_ptr->tb_id;
> +
> +	return tb_id;
> +}
> +#else
> +static inline int vrf_master_dev_idx(const struct net_device *dev)
> +{
> +	return 0;
> +}
> +
> +static inline int vrf_get_master_dev_idx(struct net *net, int idx)
> +{
> +	return 0;
> +}
> +
> +static inline int vrf_dev_table(const struct net_device *dev)
> +{
> +	return 0;
> +}
> +#endif
> +
> +#endif /* __LINUX_NET_VRF_H */
>