// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * mpls tunnels	An implementation mpls tunnels using the light weight tunnel
   *		infrastructure
   *
   * Authors:	Roopa Prabhu, <roopa@cumulusnetworks.com>

   */
  #include <linux/types.h>
  #include <linux/skbuff.h>
  #include <linux/net.h>
  #include <linux/module.h>
  #include <linux/mpls.h>
  #include <linux/vmalloc.h>
  #include <net/ip.h>
  #include <net/dst.h>
  #include <net/lwtunnel.h>
  #include <net/netevent.h>
  #include <net/netns/generic.h>
  #include <net/ip6_fib.h>
  #include <net/route.h>
  #include <net/mpls_iptunnel.h>
  #include <linux/mpls_iptunnel.h>
  #include "internal.h"
  
  static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {

  	[MPLS_IPTUNNEL_DST]	= { .len = sizeof(u32) },

  	[MPLS_IPTUNNEL_TTL]	= { .type = NLA_U8 },

  };
  
  static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
  {
  	/* The size of the layer 2.5 labels to be added for this route */
  	return en->labels * sizeof(struct mpls_shim_hdr);
  }

  static int mpls_xmit(struct sk_buff *skb)

  {
  	struct mpls_iptunnel_encap *tun_encap_info;
  	struct mpls_shim_hdr *hdr;
  	struct net_device *out_dev;
  	unsigned int hh_len;
  	unsigned int new_header_size;
  	unsigned int mtu;
  	struct dst_entry *dst = skb_dst(skb);
  	struct rtable *rt = NULL;
  	struct rt6_info *rt6 = NULL;

  	struct mpls_dev *out_mdev;

  	struct net *net;

  	int err = 0;
  	bool bos;
  	int i;
  	unsigned int ttl;

  	/* Find the output device */
  	out_dev = dst->dev;

  	net = dev_net(out_dev);

  
  	skb_orphan(skb);

  	if (!mpls_output_possible(out_dev) ||

  	    !dst->lwtstate || skb_warn_if_lro(skb))

  		goto drop;
  
  	skb_forward_csum(skb);

  	tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);

  	/* Obtain the ttl using the following set of rules.
  	 *
  	 * LWT ttl propagation setting:
  	 *  - disabled => use default TTL value from LWT
  	 *  - enabled  => use TTL value from IPv4/IPv6 header
  	 *  - default  =>
  	 *   Global ttl propagation setting:
  	 *    - disabled => use default TTL value from global setting
  	 *    - enabled => use TTL value from IPv4/IPv6 header
  	 */
  	if (dst->ops->family == AF_INET) {
  		if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  			ttl = tun_encap_info->default_ttl;
  		else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  			 !net->mpls.ip_ttl_propagate)
  			ttl = net->mpls.default_ttl;
  		else
  			ttl = ip_hdr(skb)->ttl;
  		rt = (struct rtable *)dst;
  	} else if (dst->ops->family == AF_INET6) {
  		if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
  			ttl = tun_encap_info->default_ttl;
  		else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
  			 !net->mpls.ip_ttl_propagate)
  			ttl = net->mpls.default_ttl;
  		else
  			ttl = ipv6_hdr(skb)->hop_limit;
  		rt6 = (struct rt6_info *)dst;
  	} else {
  		goto drop;
  	}

  	/* Verify the destination can hold the packet */
  	new_header_size = mpls_encap_size(tun_encap_info);
  	mtu = mpls_dev_mtu(out_dev);
  	if (mpls_pkt_too_big(skb, mtu - new_header_size))
  		goto drop;
  
  	hh_len = LL_RESERVED_SPACE(out_dev);
  	if (!out_dev->header_ops)
  		hh_len = 0;
  
  	/* Ensure there is enough space for the headers in the skb */
  	if (skb_cow(skb, hh_len + new_header_size))
  		goto drop;

  	skb_set_inner_protocol(skb, skb->protocol);
  	skb_reset_inner_network_header(skb);

  	skb_push(skb, new_header_size);

  	skb_reset_network_header(skb);
  
  	skb->dev = out_dev;
  	skb->protocol = htons(ETH_P_MPLS_UC);
  
  	/* Push the new labels */
  	hdr = mpls_hdr(skb);
  	bos = true;
  	for (i = tun_encap_info->labels - 1; i >= 0; i--) {
  		hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
  					   ttl, 0, bos);
  		bos = false;
  	}

  	mpls_stats_inc_outucastpkts(out_dev, skb);

  	if (rt) {

  		if (rt->rt_gw_family == AF_INET6)

  			err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
  					 skb);

  		else
  			err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
  					 skb);

  	} else if (rt6) {

  		if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
  			/* 6PE (RFC 4798) */
  			err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt6->rt6i_gateway.s6_addr32[3],
  					 skb);
  		} else
  			err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
  					 skb);
  	}

  	if (err)
  		net_dbg_ratelimited("%s: packet transmission failed: %d
  ",
  				    __func__, err);

  	return LWTUNNEL_XMIT_DONE;

  
  drop:

  	out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
  	if (out_mdev)
  		MPLS_INC_STATS(out_mdev, tx_errors);

  	kfree_skb(skb);
  	return -EINVAL;
  }

  static int mpls_build_state(struct net *net, struct nlattr *nla,

  			    unsigned int family, const void *cfg,

  			    struct lwtunnel_state **ts,
  			    struct netlink_ext_ack *extack)

  {
  	struct mpls_iptunnel_encap *tun_encap_info;
  	struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
  	struct lwtunnel_state *newts;

  	u8 n_labels;

  	int ret;

  	ret = nla_parse_nested_deprecated(tb, MPLS_IPTUNNEL_MAX, nla,
  					  mpls_iptunnel_policy, extack);

  	if (ret < 0)
  		return ret;

  	if (!tb[MPLS_IPTUNNEL_DST]) {
  		NL_SET_ERR_MSG(extack, "MPLS_IPTUNNEL_DST attribute is missing");

  		return -EINVAL;

  	}

  	/* determine number of labels */

  	if (nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
  			   &n_labels, NULL, extack))

  		return -EINVAL;

  	newts = lwtunnel_state_alloc(struct_size(tun_encap_info, label,
  						 n_labels));

  	if (!newts)
  		return -ENOMEM;

  	tun_encap_info = mpls_lwtunnel_encap(newts);

  	ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], n_labels,

  			     &tun_encap_info->labels, tun_encap_info->label,
  			     extack);

  	if (ret)
  		goto errout;

  
  	tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;
  
  	if (tb[MPLS_IPTUNNEL_TTL]) {
  		tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
  		/* TTL 0 implies propagate from IP header */
  		tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
  			MPLS_TTL_PROP_DISABLED :
  			MPLS_TTL_PROP_ENABLED;
  	}

  	newts->type = LWTUNNEL_ENCAP_MPLS;

  	newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
  	newts->headroom = mpls_encap_size(tun_encap_info);

  
  	*ts = newts;
  
  	return 0;
  
  errout:
  	kfree(newts);
  	*ts = NULL;
  
  	return ret;
  }
  
  static int mpls_fill_encap_info(struct sk_buff *skb,
  				struct lwtunnel_state *lwtstate)
  {
  	struct mpls_iptunnel_encap *tun_encap_info;

  	tun_encap_info = mpls_lwtunnel_encap(lwtstate);
  
  	if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
  			   tun_encap_info->label))
  		goto nla_put_failure;

  	if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
  	    nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
  		goto nla_put_failure;

  	return 0;
  
  nla_put_failure:
  	return -EMSGSIZE;
  }
  
  static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
  {
  	struct mpls_iptunnel_encap *tun_encap_info;

  	int nlsize;

  
  	tun_encap_info = mpls_lwtunnel_encap(lwtstate);

  	nlsize = nla_total_size(tun_encap_info->labels * 4);
  
  	if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
  		nlsize += nla_total_size(1);
  
  	return nlsize;

  }
  
  static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
  {
  	struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
  	struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
  	int l;

  	if (a_hdr->labels != b_hdr->labels ||
  	    a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
  	    a_hdr->default_ttl != b_hdr->default_ttl)

  		return 1;

  	for (l = 0; l < a_hdr->labels; l++)

  		if (a_hdr->label[l] != b_hdr->label[l])
  			return 1;
  	return 0;
  }
  
  static const struct lwtunnel_encap_ops mpls_iptun_ops = {
  	.build_state = mpls_build_state,

  	.xmit = mpls_xmit,

  	.fill_encap = mpls_fill_encap_info,
  	.get_encap_size = mpls_encap_nlsize,
  	.cmp_encap = mpls_encap_cmp,

  	.owner = THIS_MODULE,

  };
  
  static int __init mpls_iptunnel_init(void)
  {
  	return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
  }
  module_init(mpls_iptunnel_init);
  
  static void __exit mpls_iptunnel_exit(void)
  {
  	lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
  }
  module_exit(mpls_iptunnel_exit);

  MODULE_ALIAS_RTNL_LWT(MPLS);

  MODULE_SOFTDEP("post: mpls_gso");

  MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
  MODULE_LICENSE("GPL v2");