/* Copyright 2015-2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */

#include "packets.h"
#include "socket.h"
#include "timers.h"
#include "device.h"
#include "config.h"
#include "peer.h"
#include "uapi.h"
#include "messages.h"

#include <linux/module.h>
#include <linux/rtnetlink.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <net/icmp.h>
#include <net/rtnetlink.h>
#include <net/ip_tunnels.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_nat_core.h>

#define MAX_QUEUED_PACKETS 1024

static int init(struct net_device *dev)
{
	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
	if (!dev->tstats)
		return -ENOMEM;
	return 0;
}
static void uninit(struct net_device *dev)
{
	free_percpu(dev->tstats);
}

static int open_peer(struct wireguard_peer *peer, void *data)
{
	socket_set_peer_dst(peer);
	timers_init_peer(peer);
	packet_send_queue(peer);
	if (peer->persistent_keepalive_interval)
		packet_send_keepalive(peer);
	return 0;
}

static int open(struct net_device *dev)
{
	struct wireguard_device *wg = netdev_priv(dev);
	int rc = socket_init(wg);
	if (rc < 0)
		return rc;
	peer_for_each(wg, open_peer, NULL);
	return 0;
}

static int stop_peer(struct wireguard_peer *peer, void *data)
{
	timers_uninit_peer_wait(peer);
	noise_handshake_clear(&peer->handshake);
	noise_keypairs_clear(&peer->keypairs);
	return 0;
}

static int stop(struct net_device *dev)
{
	struct wireguard_device *wg = netdev_priv(dev);
	peer_for_each(wg, stop_peer, NULL);
	skb_queue_purge(&wg->incoming_handshakes);
	socket_uninit(wg);
	return 0;
}

static void skb_unsendable(struct sk_buff *skb, struct net_device *dev)
{
	/* This conntrack stuff is because the rate limiting needs to be applied
	 * to the original src IP, so we have to restore saddr in the IP header. */
	struct nf_conn *ct = NULL;
	enum ip_conntrack_info ctinfo;

	ct = nf_ct_get(skb, &ctinfo);
	++dev->stats.tx_errors;

	if (skb->len < sizeof(struct iphdr))
		goto free;

	if (ip_hdr(skb)->version == 4) {
		if (ct)
			ip_hdr(skb)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
	} else if (ip_hdr(skb)->version == 6) {
		if (ct)
			ipv6_hdr(skb)->saddr = ct->tuplehash[0].tuple.src.u3.in6;
		icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);
	}
free:
	kfree_skb(skb);
}

static netdev_tx_t xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct wireguard_device *wg = netdev_priv(dev);
	struct wireguard_peer *peer;
	int ret;

	if (unlikely(dev_recursion_level() > 4)) {
		net_dbg_ratelimited("Routing loop detected\n");
		skb_unsendable(skb, dev);
		return -ELOOP;
	}

	peer = routing_table_lookup_dst(&wg->peer_routing_table, skb);
	if (unlikely(!peer)) {
		net_dbg_ratelimited("No peer is configured for outgoing packet address\n");
		skb_unsendable(skb, dev);
		return -ENOKEY;
	}

	read_lock_bh(&peer->endpoint_lock);
	ret = peer->endpoint_addr.ss_family != AF_INET && peer->endpoint_addr.ss_family != AF_INET6;
	read_unlock_bh(&peer->endpoint_lock);
	if (unlikely(ret)) {
		net_dbg_ratelimited("No valid endpoint has been configured or discovered for device\n");
		peer_put(peer);
		skb_unsendable(skb, dev);
		return -EHOSTUNREACH;
	}

	/* If the queue is getting too big, we start removing the oldest packets until it's small again.
	 * We do this before adding the new packet, so we don't remove GSO segments that are in excess. */
	while (skb_queue_len(&peer->tx_packet_queue) > MAX_QUEUED_PACKETS)
		dev_kfree_skb(skb_dequeue(&peer->tx_packet_queue));

	if (!skb_is_gso(skb))
		skb->next = NULL;
	else {
		struct sk_buff *segs = skb_gso_segment(skb, 0);
		if (unlikely(IS_ERR(segs))) {
			skb_unsendable(skb, dev);
			peer_put(peer);
			return PTR_ERR(segs);
		}
		dev_kfree_skb(skb);
		skb = segs;
	}
	while (skb) {
		struct sk_buff *next = skb->next;
		skb->next = skb->prev = NULL;

		skb = skb_share_check(skb, GFP_ATOMIC);
		if (unlikely(!skb))
			continue;

		/* We only need to keep the original dst around for icmp,
		 * so at this point we're in a position to drop it. */
		skb_dst_drop(skb);

		skb_queue_tail(&peer->tx_packet_queue, skb);
		skb = next;
	}

	ret = packet_send_queue(peer);
	peer_put(peer);
	return ret;
}


static int ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
	struct wireguard_device *wg = netdev_priv(dev);

	if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
		return -EPERM;

	switch (cmd) {
	case WG_GET_DEVICE:
		return config_get_device(wg, ifr->ifr_ifru.ifru_data);
	case WG_SET_DEVICE:
		return config_set_device(wg, ifr->ifr_ifru.ifru_data);
	}
	return -EINVAL;
}

static const struct net_device_ops netdev_ops = {
	.ndo_init		= init,
	.ndo_uninit		= uninit,
	.ndo_open		= open,
	.ndo_stop		= stop,
	.ndo_start_xmit		= xmit,
	.ndo_get_stats64	= ip_tunnel_get_stats64,
	.ndo_do_ioctl		= ioctl
};

static void destruct(struct net_device *dev)
{
	struct wireguard_device *wg = netdev_priv(dev);

	mutex_lock(&wg->device_update_lock);
	peer_remove_all(wg);
	wg->incoming_port = 0;
	destroy_workqueue(wg->workqueue);
#ifdef CONFIG_WIREGUARD_PARALLEL
	padata_free(wg->parallel_send);
	padata_free(wg->parallel_receive);
	destroy_workqueue(wg->parallelqueue);
#endif
	routing_table_free(&wg->peer_routing_table);
	memzero_explicit(&wg->static_identity, sizeof(struct noise_static_identity));
	skb_queue_purge(&wg->incoming_handshakes);
	socket_uninit(wg);
	cookie_checker_uninit(&wg->cookie_checker);
	mutex_unlock(&wg->device_update_lock);

	put_net(wg->creating_net);

	pr_debug("Device %s has been deleted\n", dev->name);
	free_netdev(dev);
}

#define WG_FEATURES (NETIF_F_HW_CSUM | NETIF_F_RXCSUM | NETIF_F_SG | NETIF_F_GSO | NETIF_F_GSO_SOFTWARE | NETIF_F_HIGHDMA)

static void setup(struct net_device *dev)
{
	struct wireguard_device *wg = netdev_priv(dev);

	dev->netdev_ops = &netdev_ops;
	dev->destructor = destruct;
	dev->hard_header_len = 0;
	dev->addr_len = 0;
	dev->needed_headroom = DATA_PACKET_HEAD_ROOM;
	dev->needed_tailroom = noise_encrypted_len(MESSAGE_PADDING_MULTIPLE);
	dev->type = ARPHRD_NONE;
	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
	dev->flags |= IFF_NO_QUEUE;
#else
	dev->tx_queue_len = 0;
#endif
	dev->features |= NETIF_F_LLTX;
	dev->features |= WG_FEATURES;
	dev->hw_features |= WG_FEATURES;
	dev->hw_enc_features |= WG_FEATURES;
	dev->mtu = ETH_DATA_LEN - MESSAGE_MINIMUM_LENGTH - sizeof(struct udphdr) - max(sizeof(struct ipv6hdr), sizeof(struct iphdr));

	/* We need to keep the dst around in case of icmp replies. */
	netif_keep_dst(dev);

	memset(wg, 0, sizeof(struct wireguard_device));
}

static int newlink(struct net *src_net, struct net_device *dev, struct nlattr *tb[], struct nlattr *data[])
{
	int ret = 0;
	struct wireguard_device *wg = netdev_priv(dev);

	wg->creating_net = get_net(src_net);
	init_rwsem(&wg->static_identity.lock);
	mutex_init(&wg->socket_update_lock);
	mutex_init(&wg->device_update_lock);
	skb_queue_head_init(&wg->incoming_handshakes);
	INIT_WORK(&wg->incoming_handshakes_work, packet_process_queued_handshake_packets);
	pubkey_hashtable_init(&wg->peer_hashtable);
	index_hashtable_init(&wg->index_hashtable);
	routing_table_init(&wg->peer_routing_table);
	INIT_LIST_HEAD(&wg->peer_list);

	wg->workqueue = alloc_workqueue(KBUILD_MODNAME "-%s", WQ_UNBOUND | WQ_FREEZABLE, 0, dev->name);
	if (!wg->workqueue) {
		ret = -ENOMEM;
		goto err;
	}

#ifdef CONFIG_WIREGUARD_PARALLEL
	wg->parallelqueue = alloc_workqueue(KBUILD_MODNAME "-crypt-%s", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1, dev->name);
	if (!wg->parallelqueue) {
		ret = -ENOMEM;
		goto err;
	}

	wg->parallel_send = padata_alloc_possible(wg->parallelqueue);
	if (!wg->parallel_send) {
		ret = -ENOMEM;
		goto err;
	}
	padata_start(wg->parallel_send);

	wg->parallel_receive = padata_alloc_possible(wg->parallelqueue);
	if (!wg->parallel_receive) {
		ret = -ENOMEM;
		goto err;
	}
	padata_start(wg->parallel_receive);
#endif

	ret = cookie_checker_init(&wg->cookie_checker, wg);
	if (ret < 0)
		goto err;

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

	pr_debug("Device %s has been created\n", dev->name);

	return 0;

err:
	put_net(src_net);
	if (wg->workqueue)
		destroy_workqueue(wg->workqueue);
#ifdef CONFIG_WIREGUARD_PARALLEL
	if (wg->parallel_send)
		padata_free(wg->parallel_send);
	if (wg->parallel_receive)
		padata_free(wg->parallel_receive);
	if (wg->parallelqueue)
		destroy_workqueue(wg->parallelqueue);
#endif
	if (wg->cookie_checker.device)
		cookie_checker_uninit(&wg->cookie_checker);
	return ret;
}

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

static struct rtnl_link_ops link_ops __read_mostly = {
	.kind			= KBUILD_MODNAME,
	.priv_size		= sizeof(struct wireguard_device),
	.setup			= setup,
	.newlink		= newlink,
	.dellink		= dellink
};

int device_init(void)
{
	int ret = rtnl_link_register(&link_ops);
	if (ret < 0) {
		pr_err("Cannot register link_ops\n");
		return ret;
	}
	return ret;
}

void device_uninit(void)
{
	rtnl_link_unregister(&link_ops);
	rcu_barrier();
}