/*
   *	Linux NET3: IP/IP protocol decoder modified to support
   *		    virtual tunnel interface
   *
   *	Authors:
   *		Saurabh Mohan (saurabh.mohan@vyatta.com) 05/07/2012
   *
   *	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.
   *
   */
  
  /*
     This version of net/ipv4/ip_vti.c is cloned of net/ipv4/ipip.c
  
     For comments look at net/ipv4/ip_gre.c --ANK
   */
  
  
  #include <linux/capability.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/uaccess.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/in.h>
  #include <linux/tcp.h>
  #include <linux/udp.h>
  #include <linux/if_arp.h>

  #include <linux/init.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/if_ether.h>

  #include <linux/icmpv6.h>

  
  #include <net/sock.h>
  #include <net/ip.h>
  #include <net/icmp.h>

  #include <net/ip_tunnels.h>

  #include <net/inet_ecn.h>
  #include <net/xfrm.h>
  #include <net/net_namespace.h>
  #include <net/netns/generic.h>

  static struct rtnl_link_ops vti_link_ops __read_mostly;

  static unsigned int vti_net_id __read_mostly;

  static int vti_tunnel_init(struct net_device *dev);

  static int vti_input(struct sk_buff *skb, int nexthdr, __be32 spi,
  		     int encap_type)

  {
  	struct ip_tunnel *tunnel;
  	const struct iphdr *iph = ip_hdr(skb);

  	struct net *net = dev_net(skb->dev);
  	struct ip_tunnel_net *itn = net_generic(net, vti_net_id);

  	tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, TUNNEL_NO_KEY,
  				  iph->saddr, iph->daddr, 0);

  	if (tunnel) {

  		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
  			goto drop;
  
  		XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = tunnel;

  
  		return xfrm_input(skb, nexthdr, spi, encap_type);
  	}
  
  	return -EINVAL;
  drop:
  	kfree_skb(skb);
  	return 0;
  }
  
  static int vti_rcv(struct sk_buff *skb)
  {
  	XFRM_SPI_SKB_CB(skb)->family = AF_INET;
  	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
  
  	return vti_input(skb, ip_hdr(skb)->protocol, 0, 0);
  }
  
  static int vti_rcv_cb(struct sk_buff *skb, int err)
  {
  	unsigned short family;
  	struct net_device *dev;
  	struct pcpu_sw_netstats *tstats;
  	struct xfrm_state *x;

  	struct xfrm_mode *inner_mode;

  	struct ip_tunnel *tunnel = XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4;

  	u32 orig_mark = skb->mark;
  	int ret;

  
  	if (!tunnel)

  		return 1;

  
  	dev = tunnel->dev;
  
  	if (err) {
  		dev->stats.rx_errors++;
  		dev->stats.rx_dropped++;
  
  		return 0;

  	}

  	x = xfrm_input_state(skb);

  
  	inner_mode = x->inner_mode;
  
  	if (x->sel.family == AF_UNSPEC) {
  		inner_mode = xfrm_ip2inner_mode(x, XFRM_MODE_SKB_CB(skb)->protocol);
  		if (inner_mode == NULL) {
  			XFRM_INC_STATS(dev_net(skb->dev),
  				       LINUX_MIB_XFRMINSTATEMODEERROR);
  			return -EINVAL;
  		}
  	}
  
  	family = inner_mode->afinfo->family;

  	skb->mark = be32_to_cpu(tunnel->parms.i_key);
  	ret = xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family);
  	skb->mark = orig_mark;
  
  	if (!ret)

  		return -EPERM;
  
  	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(skb->dev)));
  	skb->dev = dev;
  
  	tstats = this_cpu_ptr(dev->tstats);
  
  	u64_stats_update_begin(&tstats->syncp);
  	tstats->rx_packets++;
  	tstats->rx_bytes += skb->len;
  	u64_stats_update_end(&tstats->syncp);
  
  	return 0;

  }

  static bool vti_state_check(const struct xfrm_state *x, __be32 dst, __be32 src)
  {
  	xfrm_address_t *daddr = (xfrm_address_t *)&dst;
  	xfrm_address_t *saddr = (xfrm_address_t *)&src;
  
  	/* if there is no transform then this tunnel is not functional.
  	 * Or if the xfrm is not mode tunnel.
  	 */
  	if (!x || x->props.mode != XFRM_MODE_TUNNEL ||
  	    x->props.family != AF_INET)
  		return false;
  
  	if (!dst)
  		return xfrm_addr_equal(saddr, &x->props.saddr, AF_INET);
  
  	if (!xfrm_state_addr_check(x, daddr, saddr, AF_INET))
  		return false;
  
  	return true;
  }

  static netdev_tx_t vti_xmit(struct sk_buff *skb, struct net_device *dev,
  			    struct flowi *fl)

  {
  	struct ip_tunnel *tunnel = netdev_priv(dev);

  	struct ip_tunnel_parm *parms = &tunnel->parms;

  	struct dst_entry *dst = skb_dst(skb);

  	struct net_device *tdev;	/* Device to other host */

  	int pkt_len = skb->len;

  	int err;

  	int mtu;

  	if (!dst) {

  		dev->stats.tx_carrier_errors++;
  		goto tx_error_icmp;
  	}

  	dst_hold(dst);

  	dst = xfrm_lookup(tunnel->net, dst, fl, NULL, 0);

  	if (IS_ERR(dst)) {

  		dev->stats.tx_carrier_errors++;
  		goto tx_error_icmp;
  	}

  	if (!vti_state_check(dst->xfrm, parms->iph.daddr, parms->iph.saddr)) {

  		dev->stats.tx_carrier_errors++;

  		dst_release(dst);

  		goto tx_error_icmp;
  	}

  	tdev = dst->dev;

  
  	if (tdev == dev) {

  		dst_release(dst);

  		dev->stats.collisions++;
  		goto tx_error;
  	}
  
  	if (tunnel->err_count > 0) {
  		if (time_before(jiffies,
  				tunnel->err_time + IPTUNNEL_ERR_TIMEO)) {
  			tunnel->err_count--;
  			dst_link_failure(skb);
  		} else
  			tunnel->err_count = 0;
  	}

  	mtu = dst_mtu(dst);
  	if (skb->len > mtu) {

  		skb_dst_update_pmtu(skb, mtu);

  		if (skb->protocol == htons(ETH_P_IP)) {
  			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
  				  htonl(mtu));
  		} else {
  			if (mtu < IPV6_MIN_MTU)
  				mtu = IPV6_MIN_MTU;
  
  			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
  		}
  
  		dst_release(dst);
  		goto tx_error;
  	}

  	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(dev)));

  	skb_dst_set(skb, dst);

  	skb->dev = skb_dst(skb)->dev;

  	err = dst_output(tunnel->net, skb->sk, skb);

  	if (net_xmit_eval(err) == 0)

  		err = pkt_len;

  	iptunnel_xmit_stats(dev, err);

  	return NETDEV_TX_OK;
  
  tx_error_icmp:
  	dst_link_failure(skb);
  tx_error:
  	dev->stats.tx_errors++;

  	kfree_skb(skb);

  	return NETDEV_TX_OK;
  }

  /* This function assumes it is being called from dev_queue_xmit()
   * and that skb is filled properly by that function.
   */
  static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
  {
  	struct ip_tunnel *tunnel = netdev_priv(dev);
  	struct flowi fl;
  
  	memset(&fl, 0, sizeof(fl));

  	switch (skb->protocol) {
  	case htons(ETH_P_IP):
  		xfrm_decode_session(skb, &fl, AF_INET);
  		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  		break;
  	case htons(ETH_P_IPV6):
  		xfrm_decode_session(skb, &fl, AF_INET6);
  		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
  		break;
  	default:
  		dev->stats.tx_errors++;
  		dev_kfree_skb(skb);
  		return NETDEV_TX_OK;
  	}

  	/* override mark with tunnel output key */
  	fl.flowi_mark = be32_to_cpu(tunnel->parms.o_key);

  	return vti_xmit(skb, dev, &fl);
  }

  static int vti4_err(struct sk_buff *skb, u32 info)
  {
  	__be32 spi;

  	__u32 mark;

  	struct xfrm_state *x;
  	struct ip_tunnel *tunnel;
  	struct ip_esp_hdr *esph;
  	struct ip_auth_hdr *ah ;
  	struct ip_comp_hdr *ipch;
  	struct net *net = dev_net(skb->dev);
  	const struct iphdr *iph = (const struct iphdr *)skb->data;
  	int protocol = iph->protocol;
  	struct ip_tunnel_net *itn = net_generic(net, vti_net_id);
  
  	tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, TUNNEL_NO_KEY,
  				  iph->daddr, iph->saddr, 0);
  	if (!tunnel)
  		return -1;

  	mark = be32_to_cpu(tunnel->parms.o_key);

  	switch (protocol) {
  	case IPPROTO_ESP:
  		esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
  		spi = esph->spi;
  		break;
  	case IPPROTO_AH:
  		ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
  		spi = ah->spi;
  		break;
  	case IPPROTO_COMP:
  		ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
  		spi = htonl(ntohs(ipch->cpi));
  		break;
  	default:
  		return 0;
  	}
  
  	switch (icmp_hdr(skb)->type) {
  	case ICMP_DEST_UNREACH:
  		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
  			return 0;
  	case ICMP_REDIRECT:
  		break;
  	default:
  		return 0;
  	}

  	x = xfrm_state_lookup(net, mark, (const xfrm_address_t *)&iph->daddr,

  			      spi, protocol, AF_INET);
  	if (!x)
  		return 0;
  
  	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
  		ipv4_update_pmtu(skb, net, info, 0, 0, protocol, 0);
  	else
  		ipv4_redirect(skb, net, 0, 0, protocol, 0);
  	xfrm_state_put(x);
  
  	return 0;
  }

  static int
  vti_tunnel_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
  {
  	int err = 0;
  	struct ip_tunnel_parm p;

  	if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
  		return -EFAULT;

  	if (cmd == SIOCADDTUNNEL || cmd == SIOCCHGTUNNEL) {

  		if (p.iph.version != 4 || p.iph.protocol != IPPROTO_IPIP ||
  		    p.iph.ihl != 5)

  			return -EINVAL;
  	}

  	if (!(p.i_flags & GRE_KEY))
  		p.i_key = 0;
  	if (!(p.o_flags & GRE_KEY))
  		p.o_key = 0;
  
  	p.i_flags = VTI_ISVTI;

  	err = ip_tunnel_ioctl(dev, &p, cmd);
  	if (err)
  		return err;

  	if (cmd != SIOCDELTUNNEL) {

  		p.i_flags |= GRE_KEY;

  		p.o_flags |= GRE_KEY;

  	}

  	if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
  		return -EFAULT;

  	return 0;
  }
  
  static const struct net_device_ops vti_netdev_ops = {
  	.ndo_init	= vti_tunnel_init,

  	.ndo_uninit	= ip_tunnel_uninit,

  	.ndo_start_xmit	= vti_tunnel_xmit,
  	.ndo_do_ioctl	= vti_tunnel_ioctl,

  	.ndo_change_mtu	= ip_tunnel_change_mtu,

  	.ndo_get_stats64 = ip_tunnel_get_stats64,

  	.ndo_get_iflink = ip_tunnel_get_iflink,

  };

  static void vti_tunnel_setup(struct net_device *dev)

  {

  	dev->netdev_ops		= &vti_netdev_ops;

  	dev->type		= ARPHRD_TUNNEL;

  	ip_tunnel_setup(dev, vti_net_id);

  }

  static int vti_tunnel_init(struct net_device *dev)

  {

  	struct ip_tunnel *tunnel = netdev_priv(dev);
  	struct iphdr *iph = &tunnel->parms.iph;
  
  	memcpy(dev->dev_addr, &iph->saddr, 4);
  	memcpy(dev->broadcast, &iph->daddr, 4);

  	dev->mtu		= ETH_DATA_LEN;

  	dev->flags		= IFF_NOARP;

  	dev->addr_len		= 4;

  	dev->features		|= NETIF_F_LLTX;

  	netif_keep_dst(dev);

  	return ip_tunnel_init(dev);

  }

  static void __net_init vti_fb_tunnel_init(struct net_device *dev)

  {
  	struct ip_tunnel *tunnel = netdev_priv(dev);
  	struct iphdr *iph = &tunnel->parms.iph;

  	iph->version		= 4;
  	iph->protocol		= IPPROTO_IPIP;
  	iph->ihl		= 5;

  }

  static struct xfrm4_protocol vti_esp4_protocol __read_mostly = {

  	.handler	=	vti_rcv,

  	.input_handler	=	vti_input,
  	.cb_handler	=	vti_rcv_cb,
  	.err_handler	=	vti4_err,
  	.priority	=	100,
  };
  
  static struct xfrm4_protocol vti_ah4_protocol __read_mostly = {
  	.handler	=	vti_rcv,
  	.input_handler	=	vti_input,
  	.cb_handler	=	vti_rcv_cb,
  	.err_handler	=	vti4_err,
  	.priority	=	100,
  };
  
  static struct xfrm4_protocol vti_ipcomp4_protocol __read_mostly = {
  	.handler	=	vti_rcv,
  	.input_handler	=	vti_input,
  	.cb_handler	=	vti_rcv_cb,
  	.err_handler	=	vti4_err,
  	.priority	=	100,

  };

  static int __net_init vti_init_net(struct net *net)
  {
  	int err;

  	struct ip_tunnel_net *itn;

  	err = ip_tunnel_init_net(net, vti_net_id, &vti_link_ops, "ip_vti0");

  	if (err)

  		return err;
  	itn = net_generic(net, vti_net_id);
  	vti_fb_tunnel_init(itn->fb_tunnel_dev);

  	return 0;

  }
  
  static void __net_exit vti_exit_net(struct net *net)
  {

  	struct ip_tunnel_net *itn = net_generic(net, vti_net_id);

  	ip_tunnel_delete_net(itn, &vti_link_ops);

  }
  
  static struct pernet_operations vti_net_ops = {
  	.init = vti_init_net,
  	.exit = vti_exit_net,
  	.id   = &vti_net_id,

  	.size = sizeof(struct ip_tunnel_net),

  };

  static int vti_tunnel_validate(struct nlattr *tb[], struct nlattr *data[],
  			       struct netlink_ext_ack *extack)

  {
  	return 0;
  }
  
  static void vti_netlink_parms(struct nlattr *data[],

  			      struct ip_tunnel_parm *parms,
  			      __u32 *fwmark)

  {
  	memset(parms, 0, sizeof(*parms));
  
  	parms->iph.protocol = IPPROTO_IPIP;
  
  	if (!data)
  		return;

  	parms->i_flags = VTI_ISVTI;

  	if (data[IFLA_VTI_LINK])
  		parms->link = nla_get_u32(data[IFLA_VTI_LINK]);
  
  	if (data[IFLA_VTI_IKEY])
  		parms->i_key = nla_get_be32(data[IFLA_VTI_IKEY]);
  
  	if (data[IFLA_VTI_OKEY])
  		parms->o_key = nla_get_be32(data[IFLA_VTI_OKEY]);
  
  	if (data[IFLA_VTI_LOCAL])

  		parms->iph.saddr = nla_get_in_addr(data[IFLA_VTI_LOCAL]);

  
  	if (data[IFLA_VTI_REMOTE])

  		parms->iph.daddr = nla_get_in_addr(data[IFLA_VTI_REMOTE]);

  	if (data[IFLA_VTI_FWMARK])
  		*fwmark = nla_get_u32(data[IFLA_VTI_FWMARK]);

  }
  
  static int vti_newlink(struct net *src_net, struct net_device *dev,

  		       struct nlattr *tb[], struct nlattr *data[],
  		       struct netlink_ext_ack *extack)

  {

  	struct ip_tunnel_parm parms;

  	__u32 fwmark = 0;

  	vti_netlink_parms(data, &parms, &fwmark);
  	return ip_tunnel_newlink(dev, tb, &parms, fwmark);

  }
  
  static int vti_changelink(struct net_device *dev, struct nlattr *tb[],

  			  struct nlattr *data[],
  			  struct netlink_ext_ack *extack)

  {

  	struct ip_tunnel *t = netdev_priv(dev);
  	__u32 fwmark = t->fwmark;

  	struct ip_tunnel_parm p;

  	vti_netlink_parms(data, &p, &fwmark);
  	return ip_tunnel_changelink(dev, tb, &p, fwmark);

  }
  
  static size_t vti_get_size(const struct net_device *dev)
  {
  	return
  		/* IFLA_VTI_LINK */
  		nla_total_size(4) +
  		/* IFLA_VTI_IKEY */
  		nla_total_size(4) +
  		/* IFLA_VTI_OKEY */
  		nla_total_size(4) +
  		/* IFLA_VTI_LOCAL */
  		nla_total_size(4) +
  		/* IFLA_VTI_REMOTE */
  		nla_total_size(4) +

  		/* IFLA_VTI_FWMARK */
  		nla_total_size(4) +

  		0;
  }
  
  static int vti_fill_info(struct sk_buff *skb, const struct net_device *dev)
  {
  	struct ip_tunnel *t = netdev_priv(dev);
  	struct ip_tunnel_parm *p = &t->parms;

  	if (nla_put_u32(skb, IFLA_VTI_LINK, p->link) ||
  	    nla_put_be32(skb, IFLA_VTI_IKEY, p->i_key) ||
  	    nla_put_be32(skb, IFLA_VTI_OKEY, p->o_key) ||
  	    nla_put_in_addr(skb, IFLA_VTI_LOCAL, p->iph.saddr) ||
  	    nla_put_in_addr(skb, IFLA_VTI_REMOTE, p->iph.daddr) ||
  	    nla_put_u32(skb, IFLA_VTI_FWMARK, t->fwmark))
  		return -EMSGSIZE;

  
  	return 0;
  }
  
  static const struct nla_policy vti_policy[IFLA_VTI_MAX + 1] = {
  	[IFLA_VTI_LINK]		= { .type = NLA_U32 },
  	[IFLA_VTI_IKEY]		= { .type = NLA_U32 },
  	[IFLA_VTI_OKEY]		= { .type = NLA_U32 },
  	[IFLA_VTI_LOCAL]	= { .len = FIELD_SIZEOF(struct iphdr, saddr) },
  	[IFLA_VTI_REMOTE]	= { .len = FIELD_SIZEOF(struct iphdr, daddr) },

  	[IFLA_VTI_FWMARK]	= { .type = NLA_U32 },

  };
  
  static struct rtnl_link_ops vti_link_ops __read_mostly = {
  	.kind		= "vti",
  	.maxtype	= IFLA_VTI_MAX,
  	.policy		= vti_policy,
  	.priv_size	= sizeof(struct ip_tunnel),
  	.setup		= vti_tunnel_setup,
  	.validate	= vti_tunnel_validate,
  	.newlink	= vti_newlink,
  	.changelink	= vti_changelink,

  	.dellink        = ip_tunnel_dellink,

  	.get_size	= vti_get_size,
  	.fill_info	= vti_fill_info,

  	.get_link_net	= ip_tunnel_get_link_net,

  };
  
  static int __init vti_init(void)
  {

  	const char *msg;

  	int err;

  	pr_info("IPv4 over IPsec tunneling driver
  ");

  	msg = "tunnel device";

  	err = register_pernet_device(&vti_net_ops);
  	if (err < 0)

  		goto pernet_dev_failed;

  	msg = "tunnel protocols";
  	err = xfrm4_protocol_register(&vti_esp4_protocol, IPPROTO_ESP);
  	if (err < 0)
  		goto xfrm_proto_esp_failed;

  	err = xfrm4_protocol_register(&vti_ah4_protocol, IPPROTO_AH);

  	if (err < 0)
  		goto xfrm_proto_ah_failed;

  	err = xfrm4_protocol_register(&vti_ipcomp4_protocol, IPPROTO_COMP);

  	if (err < 0)
  		goto xfrm_proto_comp_failed;

  	msg = "netlink interface";

  	err = rtnl_link_register(&vti_link_ops);
  	if (err < 0)
  		goto rtnl_link_failed;
  
  	return err;
  
  rtnl_link_failed:

  	xfrm4_protocol_deregister(&vti_ipcomp4_protocol, IPPROTO_COMP);

  xfrm_proto_comp_failed:

  	xfrm4_protocol_deregister(&vti_ah4_protocol, IPPROTO_AH);

  xfrm_proto_ah_failed:

  	xfrm4_protocol_deregister(&vti_esp4_protocol, IPPROTO_ESP);

  xfrm_proto_esp_failed:

  	unregister_pernet_device(&vti_net_ops);

  pernet_dev_failed:
  	pr_err("vti init: failed to register %s
  ", msg);

  	return err;
  }
  
  static void __exit vti_fini(void)
  {
  	rtnl_link_unregister(&vti_link_ops);

  	xfrm4_protocol_deregister(&vti_ipcomp4_protocol, IPPROTO_COMP);
  	xfrm4_protocol_deregister(&vti_ah4_protocol, IPPROTO_AH);
  	xfrm4_protocol_deregister(&vti_esp4_protocol, IPPROTO_ESP);

  	unregister_pernet_device(&vti_net_ops);
  }
  
  module_init(vti_init);
  module_exit(vti_fini);
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_RTNL_LINK("vti");
  MODULE_ALIAS_NETDEV("ip_vti0");