/*
 * vrf.c: device driver to encapsulate a VRF space
 *
 * Copyright (c) 2015 Cumulus Networks. All rights reserved.
 * Copyright (c) 2015 Shrijeet Mukherjee <shm@cumulusnetworks.com>
 * Copyright (c) 2015 David Ahern <dsa@cumulusnetworks.com>
 *
 * 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/netfilter.h>
#include <linux/rtnetlink.h>
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
#include <linux/hashtable.h>

#include <linux/inetdevice.h>
#include <net/arp.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/l3mdev.h>

#define RT_FL_TOS(oldflp4) \
	((oldflp4)->flowi4_tos & (IPTOS_RT_MASK | RTO_ONLINK))

#define DRV_NAME	"vrf"
#define DRV_VERSION	"1.0"

#define vrf_master_get_rcu(dev) \
	((struct net_device *)rcu_dereference(dev->rx_handler_data))

struct slave {
	struct list_head        list;
	struct net_device       *dev;
};

struct slave_queue {
	struct list_head        all_slaves;
};

struct net_vrf {
	struct slave_queue      queue;
	struct rtable           *rth;
	u32                     tb_id;
};

struct pcpu_dstats {
	u64			tx_pkts;
	u64			tx_bytes;
	u64			tx_drps;
	u64			rx_pkts;
	u64			rx_bytes;
	struct u64_stats_sync	syncp;
};

static struct dst_entry *vrf_ip_check(struct dst_entry *dst, u32 cookie)
{
	return dst;
}

static int vrf_ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	return ip_local_out(sk, skb);
}

static unsigned int vrf_v4_mtu(const struct dst_entry *dst)
{
	/* TO-DO: return max ethernet size? */
	return dst->dev->mtu;
}

static void vrf_dst_destroy(struct dst_entry *dst)
{
	/* our dst lives forever - or until the device is closed */
}

static unsigned int vrf_default_advmss(const struct dst_entry *dst)
{
	return 65535 - 40;
}

static struct dst_ops vrf_dst_ops = {
	.family		= AF_INET,
	.local_out	= vrf_ip_local_out,
	.check		= vrf_ip_check,
	.mtu		= vrf_v4_mtu,
	.destroy	= vrf_dst_destroy,
	.default_advmss	= vrf_default_advmss,
};

static bool is_ip_rx_frame(struct sk_buff *skb)
{
	switch (skb->protocol) {
	case htons(ETH_P_IP):
	case htons(ETH_P_IPV6):
		return true;
	}
	return false;
}

static void vrf_tx_error(struct net_device *vrf_dev, struct sk_buff *skb)
{
	vrf_dev->stats.tx_errors++;
	kfree_skb(skb);
}

/* 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);

		skb->dev = dev;

		return RX_HANDLER_ANOTHER;
	}
	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_process_v6_outbound(struct sk_buff *skb,
					   struct net_device *dev)
{
	vrf_tx_error(dev, skb);
	return NET_XMIT_DROP;
}

static int vrf_send_v4_prep(struct sk_buff *skb, struct flowi4 *fl4,
			    struct net_device *vrf_dev)
{
	struct rtable *rt;
	int err = 1;

	rt = ip_route_output_flow(dev_net(vrf_dev), fl4, NULL);
	if (IS_ERR(rt))
		goto out;

	/* TO-DO: what about broadcast ? */
	if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
		ip_rt_put(rt);
		goto out;
	}

	skb_dst_drop(skb);
	skb_dst_set(skb, &rt->dst);
	err = 0;
out:
	return err;
}

static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
					   struct net_device *vrf_dev)
{
	struct iphdr *ip4h = ip_hdr(skb);
	int ret = NET_XMIT_DROP;
	struct flowi4 fl4 = {
		/* needed to match OIF rule */
		.flowi4_oif = vrf_dev->ifindex,
		.flowi4_iif = LOOPBACK_IFINDEX,
		.flowi4_tos = RT_TOS(ip4h->tos),
		.flowi4_flags = FLOWI_FLAG_ANYSRC | FLOWI_FLAG_L3MDEV_SRC |
				FLOWI_FLAG_SKIP_NH_OIF,
		.daddr = ip4h->daddr,
	};

	if (vrf_send_v4_prep(skb, &fl4, vrf_dev))
		goto err;

	if (!ip4h->saddr) {
		ip4h->saddr = inet_select_addr(skb_dst(skb)->dev, 0,
					       RT_SCOPE_LINK);
	}

	ret = ip_local_out(skb->sk, skb);
	if (unlikely(net_xmit_eval(ret)))
		vrf_dev->stats.tx_errors++;
	else
		ret = NET_XMIT_SUCCESS;

out:
	return ret;
err:
	vrf_tx_error(vrf_dev, skb);
	goto out;
}

static netdev_tx_t is_ip_tx_frame(struct sk_buff *skb, struct net_device *dev)
{
	/* strip the ethernet header added for pass through VRF device */
	__skb_pull(skb, skb_network_offset(skb));

	switch (skb->protocol) {
	case htons(ETH_P_IP):
		return vrf_process_v4_outbound(skb, dev);
	case htons(ETH_P_IPV6):
		return vrf_process_v6_outbound(skb, dev);
	default:
		vrf_tx_error(dev, skb);
		return NET_XMIT_DROP;
	}
}

static netdev_tx_t vrf_xmit(struct sk_buff *skb, struct net_device *dev)
{
	netdev_tx_t ret = is_ip_tx_frame(skb, dev);

	if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN)) {
		struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);

		u64_stats_update_begin(&dstats->syncp);
		dstats->tx_pkts++;
		dstats->tx_bytes += skb->len;
		u64_stats_update_end(&dstats->syncp);
	} else {
		this_cpu_inc(dev->dstats->tx_drps);
	}

	return ret;
}

/* modelled after ip_finish_output2 */
static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	struct dst_entry *dst = skb_dst(skb);
	struct rtable *rt = (struct rtable *)dst;
	struct net_device *dev = dst->dev;
	unsigned int hh_len = LL_RESERVED_SPACE(dev);
	struct neighbour *neigh;
	u32 nexthop;
	int ret = -EINVAL;

	/* Be paranoid, rather than too clever. */
	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
		struct sk_buff *skb2;

		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
		if (!skb2) {
			ret = -ENOMEM;
			goto err;
		}
		if (skb->sk)
			skb_set_owner_w(skb2, skb->sk);

		consume_skb(skb);
		skb = skb2;
	}

	rcu_read_lock_bh();

	nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);
	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
	if (unlikely(!neigh))
		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
	if (!IS_ERR(neigh))
		ret = dst_neigh_output(dst, neigh, skb);

	rcu_read_unlock_bh();
err:
	if (unlikely(ret < 0))
		vrf_tx_error(skb->dev, skb);
	return ret;
}

static int vrf_output(struct sock *sk, struct sk_buff *skb)
{
	struct net_device *dev = skb_dst(skb)->dev;
	struct net *net = dev_net(dev);

	IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);

	skb->dev = dev;
	skb->protocol = htons(ETH_P_IP);

	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
			    net, sk, skb, NULL, dev,
			    vrf_finish_output,
			    !(IPCB(skb)->flags & IPSKB_REROUTED));
}

static void vrf_rtable_destroy(struct net_vrf *vrf)
{
	struct dst_entry *dst = (struct dst_entry *)vrf->rth;

	dst_destroy(dst);
	vrf->rth = NULL;
}

static struct rtable *vrf_rtable_create(struct net_device *dev)
{
	struct net_vrf *vrf = netdev_priv(dev);
	struct rtable *rth;

	rth = dst_alloc(&vrf_dst_ops, dev, 2,
			DST_OBSOLETE_NONE,
			(DST_HOST | DST_NOPOLICY | DST_NOXFRM));
	if (rth) {
		rth->dst.output	= vrf_output;
		rth->rt_genid	= rt_genid_ipv4(dev_net(dev));
		rth->rt_flags	= 0;
		rth->rt_type	= RTN_UNICAST;
		rth->rt_is_input = 0;
		rth->rt_iif	= 0;
		rth->rt_pmtu	= 0;
		rth->rt_gateway	= 0;
		rth->rt_uses_gateway = 0;
		rth->rt_table_id = vrf->tb_id;
		INIT_LIST_HEAD(&rth->rt_uncached);
		rth->rt_uncached_list = NULL;
	}

	return rth;
}

/**************************** device handling ********************/

/* cycle interface to flush neighbor cache and move routes across tables */
static void cycle_netdev(struct net_device *dev)
{
	unsigned int flags = dev->flags;
	int ret;

	if (!netif_running(dev))
		return;

	ret = dev_change_flags(dev, flags & ~IFF_UP);
	if (ret >= 0)
		ret = dev_change_flags(dev, flags);

	if (ret < 0) {
		netdev_err(dev,
			   "Failed to cycle device %s; route tables might be wrong!\n",
			   dev->name);
	}
}

static struct slave *__vrf_find_slave_dev(struct slave_queue *queue,
					  struct net_device *dev)
{
	struct list_head *head = &queue->all_slaves;
	struct slave *slave;

	list_for_each_entry(slave, head, list) {
		if (slave->dev == dev)
			return slave;
	}

	return NULL;
}

/* inverse of __vrf_insert_slave */
static void __vrf_remove_slave(struct slave_queue *queue, struct slave *slave)
{
	list_del(&slave->list);
}

static void __vrf_insert_slave(struct slave_queue *queue, struct slave *slave)
{
	list_add(&slave->list, &queue->all_slaves);
}

static int do_vrf_add_slave(struct net_device *dev, struct net_device *port_dev)
{
	struct slave *slave = kzalloc(sizeof(*slave), GFP_KERNEL);
	struct net_vrf *vrf = netdev_priv(dev);
	struct slave_queue *queue = &vrf->queue;
	int ret = -ENOMEM;

	if (!slave)
		goto out_fail;

	slave->dev = port_dev;

	/* register the packet handler for slave ports */
	ret = netdev_rx_handler_register(port_dev, vrf_handle_frame, dev);
	if (ret) {
		netdev_err(port_dev,
			   "Device %s failed to register rx_handler\n",
			   port_dev->name);
		goto out_fail;
	}

	ret = netdev_master_upper_dev_link(port_dev, dev);
	if (ret < 0)
		goto out_unregister;

	port_dev->priv_flags |= IFF_L3MDEV_SLAVE;
	__vrf_insert_slave(queue, slave);
	cycle_netdev(port_dev);

	return 0;

out_unregister:
	netdev_rx_handler_unregister(port_dev);
out_fail:
	kfree(slave);
	return ret;
}

static int vrf_add_slave(struct net_device *dev, struct net_device *port_dev)
{
	if (netif_is_l3_master(port_dev) || netif_is_l3_slave(port_dev))
		return -EINVAL;

	return do_vrf_add_slave(dev, port_dev);
}

/* inverse of do_vrf_add_slave */
static int do_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;

	netdev_upper_dev_unlink(port_dev, dev);
	port_dev->priv_flags &= ~IFF_L3MDEV_SLAVE;

	netdev_rx_handler_unregister(port_dev);

	cycle_netdev(port_dev);

	slave = __vrf_find_slave_dev(queue, port_dev);
	if (slave)
		__vrf_remove_slave(queue, slave);

	kfree(slave);

	return 0;
}

static int vrf_del_slave(struct net_device *dev, struct net_device *port_dev)
{
	return do_vrf_del_slave(dev, port_dev);
}

static void vrf_dev_uninit(struct net_device *dev)
{
	struct net_vrf *vrf = netdev_priv(dev);
	struct slave_queue *queue = &vrf->queue;
	struct list_head *head = &queue->all_slaves;
	struct slave *slave, *next;

	vrf_rtable_destroy(vrf);

	list_for_each_entry_safe(slave, next, head, list)
		vrf_del_slave(dev, slave->dev);

	free_percpu(dev->dstats);
	dev->dstats = NULL;
}

static int vrf_dev_init(struct net_device *dev)
{
	struct net_vrf *vrf = netdev_priv(dev);

	INIT_LIST_HEAD(&vrf->queue.all_slaves);

	dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
	if (!dev->dstats)
		goto out_nomem;

	/* create the default dst which points back to us */
	vrf->rth = vrf_rtable_create(dev);
	if (!vrf->rth)
		goto out_stats;

	dev->flags = IFF_MASTER | IFF_NOARP;

	return 0;

out_stats:
	free_percpu(dev->dstats);
	dev->dstats = NULL;
out_nomem:
	return -ENOMEM;
}

static const struct net_device_ops vrf_netdev_ops = {
	.ndo_init		= vrf_dev_init,
	.ndo_uninit		= vrf_dev_uninit,
	.ndo_start_xmit		= vrf_xmit,
	.ndo_get_stats64	= vrf_get_stats64,
	.ndo_add_slave		= vrf_add_slave,
	.ndo_del_slave		= vrf_del_slave,
};

static u32 vrf_fib_table(const struct net_device *dev)
{
	struct net_vrf *vrf = netdev_priv(dev);

	return vrf->tb_id;
}

static struct rtable *vrf_get_rtable(const struct net_device *dev,
				     const struct flowi4 *fl4)
{
	struct rtable *rth = NULL;

	if (!(fl4->flowi4_flags & FLOWI_FLAG_L3MDEV_SRC)) {
		struct net_vrf *vrf = netdev_priv(dev);

		rth = vrf->rth;
		atomic_inc(&rth->dst.__refcnt);
	}

	return rth;
}

/* called under rcu_read_lock */
static void vrf_get_saddr(struct net_device *dev, struct flowi4 *fl4)
{
	struct fib_result res = { .tclassid = 0 };
	struct net *net = dev_net(dev);
	u32 orig_tos = fl4->flowi4_tos;
	u8 flags = fl4->flowi4_flags;
	u8 scope = fl4->flowi4_scope;
	u8 tos = RT_FL_TOS(fl4);

	if (unlikely(!fl4->daddr))
		return;

	fl4->flowi4_flags |= FLOWI_FLAG_SKIP_NH_OIF;
	fl4->flowi4_iif = LOOPBACK_IFINDEX;
	fl4->flowi4_tos = tos & IPTOS_RT_MASK;
	fl4->flowi4_scope = ((tos & RTO_ONLINK) ?
			     RT_SCOPE_LINK : RT_SCOPE_UNIVERSE);

	if (!fib_lookup(net, fl4, &res, 0)) {
		if (res.type == RTN_LOCAL)
			fl4->saddr = res.fi->fib_prefsrc ? : fl4->daddr;
		else
			fib_select_path(net, &res, fl4, -1);
	}

	fl4->flowi4_flags = flags;
	fl4->flowi4_tos = orig_tos;
	fl4->flowi4_scope = scope;
}

static const struct l3mdev_ops vrf_l3mdev_ops = {
	.l3mdev_fib_table	= vrf_fib_table,
	.l3mdev_get_rtable	= vrf_get_rtable,
	.l3mdev_get_saddr	= vrf_get_saddr,
};

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->l3mdev_ops = &vrf_l3mdev_ops;
	dev->ethtool_ops = &vrf_ethtool_ops;
	dev->destructor = free_netdev;

	/* Fill in device structure with ethernet-generic values. */
	eth_hw_addr_random(dev);

	/* don't acquire vrf device's netif_tx_lock when transmitting */
	dev->features |= NETIF_F_LLTX;

	/* don't allow vrf devices to change network namespaces. */
	dev->features |= NETIF_F_NETNS_LOCAL;
}

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 void vrf_dellink(struct net_device *dev, struct list_head *head)
{
	unregister_netdevice_queue(dev, head);
}

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]);

	dev->priv_flags |= IFF_L3MDEV_MASTER;

	err = register_netdevice(dev);
	if (err < 0)
		goto out_fail;

	return 0;

out_fail:
	free_netdev(dev);
	return err;
}

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 vrf_device_event(struct notifier_block *unused,
			    unsigned long event, void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

	/* only care about unregister events to drop slave references */
	if (event == NETDEV_UNREGISTER) {
		struct net_device *vrf_dev;

		if (!netif_is_l3_slave(dev))
			goto out;

		vrf_dev = netdev_master_upper_dev_get(dev);
		vrf_del_slave(vrf_dev, dev);
	}
out:
	return NOTIFY_DONE;
}

static struct notifier_block vrf_notifier_block __read_mostly = {
	.notifier_call = vrf_device_event,
};

static int __init vrf_init_module(void)
{
	int rc;

	vrf_dst_ops.kmem_cachep =
		kmem_cache_create("vrf_ip_dst_cache",
				  sizeof(struct rtable), 0,
				  SLAB_HWCACHE_ALIGN,
				  NULL);

	if (!vrf_dst_ops.kmem_cachep)
		return -ENOMEM;

	register_netdevice_notifier(&vrf_notifier_block);

	rc = rtnl_link_register(&vrf_link_ops);
	if (rc < 0)
		goto error;

	return 0;

error:
	unregister_netdevice_notifier(&vrf_notifier_block);
	kmem_cache_destroy(vrf_dst_ops.kmem_cachep);
	return rc;
}

static void __exit vrf_cleanup_module(void)
{
	rtnl_link_unregister(&vrf_link_ops);
	unregister_netdevice_notifier(&vrf_notifier_block);
	kmem_cache_destroy(vrf_dst_ops.kmem_cachep);
}

module_init(vrf_init_module);
module_exit(vrf_cleanup_module);
MODULE_AUTHOR("Shrijeet Mukherjee, David Ahern");
MODULE_DESCRIPTION("Device driver to instantiate VRF domains");
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);
MODULE_VERSION(DRV_VERSION);