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ip6_tunnel.c

/*
 *    IPv6 tunneling device
 *    Linux INET6 implementation
 *
 *    Authors:
 *    Ville Nuorvala          <vnuorval@tcs.hut.fi>
 *    Yasuyuki Kozakai  <kozakai@linux-ipv6.org>
 *
 *    $Id$
 *
 *      Based on:
 *      linux/net/ipv6/sit.c and linux/net/ipv4/ipip.c
 *
 *      RFC 2473
 *
 *    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/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/sockios.h>
#include <linux/icmp.h>
#include <linux/if.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/if_tunnel.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmpv6.h>
#include <linux/init.h>
#include <linux/route.h>
#include <linux/rtnetlink.h>
#include <linux/netfilter_ipv6.h>

#include <asm/uaccess.h>
#include <asm/atomic.h>

#include <net/icmp.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/ip6_tunnel.h>
#include <net/xfrm.h>
#include <net/dsfield.h>
#include <net/inet_ecn.h>

MODULE_AUTHOR("Ville Nuorvala");
MODULE_DESCRIPTION("IPv6 tunneling device");
MODULE_LICENSE("GPL");

#define IPV6_TLV_TEL_DST_SIZE 8

#ifdef IP6_TNL_DEBUG
#define IP6_TNL_TRACE(x...) printk(KERN_DEBUG "%s:" x "\n", __FUNCTION__)
#else
#define IP6_TNL_TRACE(x...) do {;} while(0)
#endif

#define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
#define IPV6_TCLASS_SHIFT 20

#define HASH_SIZE  32

#define HASH(addr) ((__force u32)((addr)->s6_addr32[0] ^ (addr)->s6_addr32[1] ^ \
                 (addr)->s6_addr32[2] ^ (addr)->s6_addr32[3]) & \
                (HASH_SIZE - 1))

static int ip6_fb_tnl_dev_init(struct net_device *dev);
static int ip6_tnl_dev_init(struct net_device *dev);
static void ip6_tnl_dev_setup(struct net_device *dev);

/* the IPv6 tunnel fallback device */
static struct net_device *ip6_fb_tnl_dev;


/* lists for storing tunnels in use */
static struct ip6_tnl *tnls_r_l[HASH_SIZE];
static struct ip6_tnl *tnls_wc[1];
static struct ip6_tnl **tnls[2] = { tnls_wc, tnls_r_l };

/* lock for the tunnel lists */
static DEFINE_RWLOCK(ip6_tnl_lock);

static inline struct dst_entry *ip6_tnl_dst_check(struct ip6_tnl *t)
{
      struct dst_entry *dst = t->dst_cache;

      if (dst && dst->obsolete &&
          dst->ops->check(dst, t->dst_cookie) == NULL) {
            t->dst_cache = NULL;
            dst_release(dst);
            return NULL;
      }

      return dst;
}

static inline void ip6_tnl_dst_reset(struct ip6_tnl *t)
{
      dst_release(t->dst_cache);
      t->dst_cache = NULL;
}

static inline void ip6_tnl_dst_store(struct ip6_tnl *t, struct dst_entry *dst)
{
      struct rt6_info *rt = (struct rt6_info *) dst;
      t->dst_cookie = rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
      dst_release(t->dst_cache);
      t->dst_cache = dst;
}

/**
 * ip6_tnl_lookup - fetch tunnel matching the end-point addresses
 *   @remote: the address of the tunnel exit-point
 *   @local: the address of the tunnel entry-point
 *
 * Return:
 *   tunnel matching given end-points if found,
 *   else fallback tunnel if its device is up,
 *   else %NULL
 **/

static struct ip6_tnl *
ip6_tnl_lookup(struct in6_addr *remote, struct in6_addr *local)
{
      unsigned h0 = HASH(remote);
      unsigned h1 = HASH(local);
      struct ip6_tnl *t;

      for (t = tnls_r_l[h0 ^ h1]; t; t = t->next) {
            if (ipv6_addr_equal(local, &t->parms.laddr) &&
                ipv6_addr_equal(remote, &t->parms.raddr) &&
                (t->dev->flags & IFF_UP))
                  return t;
      }
      if ((t = tnls_wc[0]) != NULL && (t->dev->flags & IFF_UP))
            return t;

      return NULL;
}

/**
 * ip6_tnl_bucket - get head of list matching given tunnel parameters
 *   @p: parameters containing tunnel end-points
 *
 * Description:
 *   ip6_tnl_bucket() returns the head of the list matching the
 *   &struct in6_addr entries laddr and raddr in @p.
 *
 * Return: head of IPv6 tunnel list
 **/

static struct ip6_tnl **
ip6_tnl_bucket(struct ip6_tnl_parm *p)
{
      struct in6_addr *remote = &p->raddr;
      struct in6_addr *local = &p->laddr;
      unsigned h = 0;
      int prio = 0;

      if (!ipv6_addr_any(remote) || !ipv6_addr_any(local)) {
            prio = 1;
            h = HASH(remote) ^ HASH(local);
      }
      return &tnls[prio][h];
}

/**
 * ip6_tnl_link - add tunnel to hash table
 *   @t: tunnel to be added
 **/

static void
ip6_tnl_link(struct ip6_tnl *t)
{
      struct ip6_tnl **tp = ip6_tnl_bucket(&t->parms);

      t->next = *tp;
      write_lock_bh(&ip6_tnl_lock);
      *tp = t;
      write_unlock_bh(&ip6_tnl_lock);
}

/**
 * ip6_tnl_unlink - remove tunnel from hash table
 *   @t: tunnel to be removed
 **/

static void
ip6_tnl_unlink(struct ip6_tnl *t)
{
      struct ip6_tnl **tp;

      for (tp = ip6_tnl_bucket(&t->parms); *tp; tp = &(*tp)->next) {
            if (t == *tp) {
                  write_lock_bh(&ip6_tnl_lock);
                  *tp = t->next;
                  write_unlock_bh(&ip6_tnl_lock);
                  break;
            }
      }
}

/**
 * ip6_tnl_create() - create a new tunnel
 *   @p: tunnel parameters
 *   @pt: pointer to new tunnel
 *
 * Description:
 *   Create tunnel matching given parameters.
 *
 * Return:
 *   created tunnel or NULL
 **/

static struct ip6_tnl *ip6_tnl_create(struct ip6_tnl_parm *p)
{
      struct net_device *dev;
      struct ip6_tnl *t;
      char name[IFNAMSIZ];
      int err;

      if (p->name[0]) {
            strlcpy(name, p->name, IFNAMSIZ);
      } else {
            int i;
            for (i = 1; i < IP6_TNL_MAX; i++) {
                  sprintf(name, "ip6tnl%d", i);
                  if (__dev_get_by_name(&init_net, name) == NULL)
                        break;
            }
            if (i == IP6_TNL_MAX)
                  goto failed;
      }
      dev = alloc_netdev(sizeof (*t), name, ip6_tnl_dev_setup);
      if (dev == NULL)
            goto failed;

      t = netdev_priv(dev);
      dev->init = ip6_tnl_dev_init;
      t->parms = *p;

      if ((err = register_netdevice(dev)) < 0) {
            free_netdev(dev);
            goto failed;
      }
      dev_hold(dev);
      ip6_tnl_link(t);
      return t;
failed:
      return NULL;
}

/**
 * ip6_tnl_locate - find or create tunnel matching given parameters
 *   @p: tunnel parameters
 *   @create: != 0 if allowed to create new tunnel if no match found
 *
 * Description:
 *   ip6_tnl_locate() first tries to locate an existing tunnel
 *   based on @parms. If this is unsuccessful, but @create is set a new
 *   tunnel device is created and registered for use.
 *
 * Return:
 *   matching tunnel or NULL
 **/

static struct ip6_tnl *ip6_tnl_locate(struct ip6_tnl_parm *p, int create)
{
      struct in6_addr *remote = &p->raddr;
      struct in6_addr *local = &p->laddr;
      struct ip6_tnl *t;

      for (t = *ip6_tnl_bucket(p); t; t = t->next) {
            if (ipv6_addr_equal(local, &t->parms.laddr) &&
                ipv6_addr_equal(remote, &t->parms.raddr))
                  return t;
      }
      if (!create)
            return NULL;
      return ip6_tnl_create(p);
}

/**
 * ip6_tnl_dev_uninit - tunnel device uninitializer
 *   @dev: the device to be destroyed
 *
 * Description:
 *   ip6_tnl_dev_uninit() removes tunnel from its list
 **/

static void
ip6_tnl_dev_uninit(struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);

      if (dev == ip6_fb_tnl_dev) {
            write_lock_bh(&ip6_tnl_lock);
            tnls_wc[0] = NULL;
            write_unlock_bh(&ip6_tnl_lock);
      } else {
            ip6_tnl_unlink(t);
      }
      ip6_tnl_dst_reset(t);
      dev_put(dev);
}

/**
 * parse_tvl_tnl_enc_lim - handle encapsulation limit option
 *   @skb: received socket buffer
 *
 * Return:
 *   0 if none was found,
 *   else index to encapsulation limit
 **/

static __u16
parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw)
{
      struct ipv6hdr *ipv6h = (struct ipv6hdr *) raw;
      __u8 nexthdr = ipv6h->nexthdr;
      __u16 off = sizeof (*ipv6h);

      while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) {
            __u16 optlen = 0;
            struct ipv6_opt_hdr *hdr;
            if (raw + off + sizeof (*hdr) > skb->data &&
                !pskb_may_pull(skb, raw - skb->data + off + sizeof (*hdr)))
                  break;

            hdr = (struct ipv6_opt_hdr *) (raw + off);
            if (nexthdr == NEXTHDR_FRAGMENT) {
                  struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr;
                  if (frag_hdr->frag_off)
                        break;
                  optlen = 8;
            } else if (nexthdr == NEXTHDR_AUTH) {
                  optlen = (hdr->hdrlen + 2) << 2;
            } else {
                  optlen = ipv6_optlen(hdr);
            }
            if (nexthdr == NEXTHDR_DEST) {
                  __u16 i = off + 2;
                  while (1) {
                        struct ipv6_tlv_tnl_enc_lim *tel;

                        /* No more room for encapsulation limit */
                        if (i + sizeof (*tel) > off + optlen)
                              break;

                        tel = (struct ipv6_tlv_tnl_enc_lim *) &raw[i];
                        /* return index of option if found and valid */
                        if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT &&
                            tel->length == 1)
                              return i;
                        /* else jump to next option */
                        if (tel->type)
                              i += tel->length + 2;
                        else
                              i++;
                  }
            }
            nexthdr = hdr->nexthdr;
            off += optlen;
      }
      return 0;
}

/**
 * ip6_tnl_err - tunnel error handler
 *
 * Description:
 *   ip6_tnl_err() should handle errors in the tunnel according
 *   to the specifications in RFC 2473.
 **/

static int
ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
          int *type, int *code, int *msg, __u32 *info, int offset)
{
      struct ipv6hdr *ipv6h = (struct ipv6hdr *) skb->data;
      struct ip6_tnl *t;
      int rel_msg = 0;
      int rel_type = ICMPV6_DEST_UNREACH;
      int rel_code = ICMPV6_ADDR_UNREACH;
      __u32 rel_info = 0;
      __u16 len;
      int err = -ENOENT;

      /* If the packet doesn't contain the original IPv6 header we are
         in trouble since we might need the source address for further
         processing of the error. */

      read_lock(&ip6_tnl_lock);
      if ((t = ip6_tnl_lookup(&ipv6h->daddr, &ipv6h->saddr)) == NULL)
            goto out;

      if (t->parms.proto != ipproto && t->parms.proto != 0)
            goto out;

      err = 0;

      switch (*type) {
            __u32 teli;
            struct ipv6_tlv_tnl_enc_lim *tel;
            __u32 mtu;
      case ICMPV6_DEST_UNREACH:
            if (net_ratelimit())
                  printk(KERN_WARNING
                         "%s: Path to destination invalid "
                         "or inactive!\n", t->parms.name);
            rel_msg = 1;
            break;
      case ICMPV6_TIME_EXCEED:
            if ((*code) == ICMPV6_EXC_HOPLIMIT) {
                  if (net_ratelimit())
                        printk(KERN_WARNING
                               "%s: Too small hop limit or "
                               "routing loop in tunnel!\n",
                               t->parms.name);
                  rel_msg = 1;
            }
            break;
      case ICMPV6_PARAMPROB:
            teli = 0;
            if ((*code) == ICMPV6_HDR_FIELD)
                  teli = parse_tlv_tnl_enc_lim(skb, skb->data);

            if (teli && teli == *info - 2) {
                  tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->data[teli];
                  if (tel->encap_limit == 0) {
                        if (net_ratelimit())
                              printk(KERN_WARNING
                                     "%s: Too small encapsulation "
                                     "limit or routing loop in "
                                     "tunnel!\n", t->parms.name);
                        rel_msg = 1;
                  }
            } else if (net_ratelimit()) {
                  printk(KERN_WARNING
                         "%s: Recipient unable to parse tunneled "
                         "packet!\n ", t->parms.name);
            }
            break;
      case ICMPV6_PKT_TOOBIG:
            mtu = *info - offset;
            if (mtu < IPV6_MIN_MTU)
                  mtu = IPV6_MIN_MTU;
            t->dev->mtu = mtu;

            if ((len = sizeof (*ipv6h) + ntohs(ipv6h->payload_len)) > mtu) {
                  rel_type = ICMPV6_PKT_TOOBIG;
                  rel_code = 0;
                  rel_info = mtu;
                  rel_msg = 1;
            }
            break;
      }

      *type = rel_type;
      *code = rel_code;
      *info = rel_info;
      *msg = rel_msg;

out:
      read_unlock(&ip6_tnl_lock);
      return err;
}

static int
ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         int type, int code, int offset, __be32 info)
{
      int rel_msg = 0;
      int rel_type = type;
      int rel_code = code;
      __u32 rel_info = ntohl(info);
      int err;
      struct sk_buff *skb2;
      struct iphdr *eiph;
      struct flowi fl;
      struct rtable *rt;

      err = ip6_tnl_err(skb, IPPROTO_IPIP, opt, &rel_type, &rel_code,
                    &rel_msg, &rel_info, offset);
      if (err < 0)
            return err;

      if (rel_msg == 0)
            return 0;

      switch (rel_type) {
      case ICMPV6_DEST_UNREACH:
            if (rel_code != ICMPV6_ADDR_UNREACH)
                  return 0;
            rel_type = ICMP_DEST_UNREACH;
            rel_code = ICMP_HOST_UNREACH;
            break;
      case ICMPV6_PKT_TOOBIG:
            if (rel_code != 0)
                  return 0;
            rel_type = ICMP_DEST_UNREACH;
            rel_code = ICMP_FRAG_NEEDED;
            break;
      default:
            return 0;
      }

      if (!pskb_may_pull(skb, offset + sizeof(struct iphdr)))
            return 0;

      skb2 = skb_clone(skb, GFP_ATOMIC);
      if (!skb2)
            return 0;

      dst_release(skb2->dst);
      skb2->dst = NULL;
      skb_pull(skb2, offset);
      skb_reset_network_header(skb2);
      eiph = ip_hdr(skb2);

      /* Try to guess incoming interface */
      memset(&fl, 0, sizeof(fl));
      fl.fl4_dst = eiph->saddr;
      fl.fl4_tos = RT_TOS(eiph->tos);
      fl.proto = IPPROTO_IPIP;
      if (ip_route_output_key(&rt, &fl))
            goto out;

      skb2->dev = rt->u.dst.dev;

      /* route "incoming" packet */
      if (rt->rt_flags & RTCF_LOCAL) {
            ip_rt_put(rt);
            rt = NULL;
            fl.fl4_dst = eiph->daddr;
            fl.fl4_src = eiph->saddr;
            fl.fl4_tos = eiph->tos;
            if (ip_route_output_key(&rt, &fl) ||
                rt->u.dst.dev->type != ARPHRD_TUNNEL) {
                  ip_rt_put(rt);
                  goto out;
            }
      } else {
            ip_rt_put(rt);
            if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos,
                           skb2->dev) ||
                skb2->dst->dev->type != ARPHRD_TUNNEL)
                  goto out;
      }

      /* change mtu on this route */
      if (rel_type == ICMP_DEST_UNREACH && rel_code == ICMP_FRAG_NEEDED) {
            if (rel_info > dst_mtu(skb2->dst))
                  goto out;

            skb2->dst->ops->update_pmtu(skb2->dst, rel_info);
      }

      icmp_send(skb2, rel_type, rel_code, htonl(rel_info));

out:
      kfree_skb(skb2);
      return 0;
}

static int
ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         int type, int code, int offset, __be32 info)
{
      int rel_msg = 0;
      int rel_type = type;
      int rel_code = code;
      __u32 rel_info = ntohl(info);
      int err;

      err = ip6_tnl_err(skb, IPPROTO_IPV6, opt, &rel_type, &rel_code,
                    &rel_msg, &rel_info, offset);
      if (err < 0)
            return err;

      if (rel_msg && pskb_may_pull(skb, offset + sizeof(struct ipv6hdr))) {
            struct rt6_info *rt;
            struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

            if (!skb2)
                  return 0;

            dst_release(skb2->dst);
            skb2->dst = NULL;
            skb_pull(skb2, offset);
            skb_reset_network_header(skb2);

            /* Try to guess incoming interface */
            rt = rt6_lookup(&ipv6_hdr(skb2)->saddr, NULL, 0, 0);

            if (rt && rt->rt6i_dev)
                  skb2->dev = rt->rt6i_dev;

            icmpv6_send(skb2, rel_type, rel_code, rel_info, skb2->dev);

            if (rt)
                  dst_release(&rt->u.dst);

            kfree_skb(skb2);
      }

      return 0;
}

static void ip4ip6_dscp_ecn_decapsulate(struct ip6_tnl *t,
                              struct ipv6hdr *ipv6h,
                              struct sk_buff *skb)
{
      __u8 dsfield = ipv6_get_dsfield(ipv6h) & ~INET_ECN_MASK;

      if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
            ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, dsfield);

      if (INET_ECN_is_ce(dsfield))
            IP_ECN_set_ce(ip_hdr(skb));
}

static void ip6ip6_dscp_ecn_decapsulate(struct ip6_tnl *t,
                              struct ipv6hdr *ipv6h,
                              struct sk_buff *skb)
{
      if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
            ipv6_copy_dscp(ipv6h, ipv6_hdr(skb));

      if (INET_ECN_is_ce(ipv6_get_dsfield(ipv6h)))
            IP6_ECN_set_ce(ipv6_hdr(skb));
}

static inline int ip6_tnl_rcv_ctl(struct ip6_tnl *t)
{
      struct ip6_tnl_parm *p = &t->parms;
      int ret = 0;

      if (p->flags & IP6_TNL_F_CAP_RCV) {
            struct net_device *ldev = NULL;

            if (p->link)
                  ldev = dev_get_by_index(&init_net, p->link);

            if ((ipv6_addr_is_multicast(&p->laddr) ||
                 likely(ipv6_chk_addr(&p->laddr, ldev, 0))) &&
                likely(!ipv6_chk_addr(&p->raddr, NULL, 0)))
                  ret = 1;

            if (ldev)
                  dev_put(ldev);
      }
      return ret;
}

/**
 * ip6_tnl_rcv - decapsulate IPv6 packet and retransmit it locally
 *   @skb: received socket buffer
 *   @protocol: ethernet protocol ID
 *   @dscp_ecn_decapsulate: the function to decapsulate DSCP code and ECN
 *
 * Return: 0
 **/

static int ip6_tnl_rcv(struct sk_buff *skb, __u16 protocol,
                   __u8 ipproto,
                   void (*dscp_ecn_decapsulate)(struct ip6_tnl *t,
                                        struct ipv6hdr *ipv6h,
                                        struct sk_buff *skb))
{
      struct ip6_tnl *t;
      struct ipv6hdr *ipv6h = ipv6_hdr(skb);

      read_lock(&ip6_tnl_lock);

      if ((t = ip6_tnl_lookup(&ipv6h->saddr, &ipv6h->daddr)) != NULL) {
            if (t->parms.proto != ipproto && t->parms.proto != 0) {
                  read_unlock(&ip6_tnl_lock);
                  goto discard;
            }

            if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                  read_unlock(&ip6_tnl_lock);
                  goto discard;
            }

            if (!ip6_tnl_rcv_ctl(t)) {
                  t->stat.rx_dropped++;
                  read_unlock(&ip6_tnl_lock);
                  goto discard;
            }
            secpath_reset(skb);
            skb->mac_header = skb->network_header;
            skb_reset_network_header(skb);
            skb->protocol = htons(protocol);
            skb->pkt_type = PACKET_HOST;
            memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
            skb->dev = t->dev;
            dst_release(skb->dst);
            skb->dst = NULL;
            nf_reset(skb);

            dscp_ecn_decapsulate(t, ipv6h, skb);

            t->stat.rx_packets++;
            t->stat.rx_bytes += skb->len;
            netif_rx(skb);
            read_unlock(&ip6_tnl_lock);
            return 0;
      }
      read_unlock(&ip6_tnl_lock);
      return 1;

discard:
      kfree_skb(skb);
      return 0;
}

static int ip4ip6_rcv(struct sk_buff *skb)
{
      return ip6_tnl_rcv(skb, ETH_P_IP, IPPROTO_IPIP,
                     ip4ip6_dscp_ecn_decapsulate);
}

static int ip6ip6_rcv(struct sk_buff *skb)
{
      return ip6_tnl_rcv(skb, ETH_P_IPV6, IPPROTO_IPV6,
                     ip6ip6_dscp_ecn_decapsulate);
}

struct ipv6_tel_txoption {
      struct ipv6_txoptions ops;
      __u8 dst_opt[8];
};

static void init_tel_txopt(struct ipv6_tel_txoption *opt, __u8 encap_limit)
{
      memset(opt, 0, sizeof(struct ipv6_tel_txoption));

      opt->dst_opt[2] = IPV6_TLV_TNL_ENCAP_LIMIT;
      opt->dst_opt[3] = 1;
      opt->dst_opt[4] = encap_limit;
      opt->dst_opt[5] = IPV6_TLV_PADN;
      opt->dst_opt[6] = 1;

      opt->ops.dst0opt = (struct ipv6_opt_hdr *) opt->dst_opt;
      opt->ops.opt_nflen = 8;
}

/**
 * ip6_tnl_addr_conflict - compare packet addresses to tunnel's own
 *   @t: the outgoing tunnel device
 *   @hdr: IPv6 header from the incoming packet
 *
 * Description:
 *   Avoid trivial tunneling loop by checking that tunnel exit-point
 *   doesn't match source of incoming packet.
 *
 * Return:
 *   1 if conflict,
 *   0 else
 **/

static inline int
ip6_tnl_addr_conflict(struct ip6_tnl *t, struct ipv6hdr *hdr)
{
      return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
}

static inline int ip6_tnl_xmit_ctl(struct ip6_tnl *t)
{
      struct ip6_tnl_parm *p = &t->parms;
      int ret = 0;

      if (p->flags & IP6_TNL_F_CAP_XMIT) {
            struct net_device *ldev = NULL;

            if (p->link)
                  ldev = dev_get_by_index(&init_net, p->link);

            if (unlikely(!ipv6_chk_addr(&p->laddr, ldev, 0)))
                  printk(KERN_WARNING
                         "%s xmit: Local address not yet configured!\n",
                         p->name);
            else if (!ipv6_addr_is_multicast(&p->raddr) &&
                   unlikely(ipv6_chk_addr(&p->raddr, NULL, 0)))
                  printk(KERN_WARNING
                         "%s xmit: Routing loop! "
                         "Remote address found on this node!\n",
                         p->name);
            else
                  ret = 1;
            if (ldev)
                  dev_put(ldev);
      }
      return ret;
}
/**
 * ip6_tnl_xmit2 - encapsulate packet and send
 *   @skb: the outgoing socket buffer
 *   @dev: the outgoing tunnel device
 *   @dsfield: dscp code for outer header
 *   @fl: flow of tunneled packet
 *   @encap_limit: encapsulation limit
 *   @pmtu: Path MTU is stored if packet is too big
 *
 * Description:
 *   Build new header and do some sanity checks on the packet before sending
 *   it.
 *
 * Return:
 *   0 on success
 *   -1 fail
 *   %-EMSGSIZE message too big. return mtu in this case.
 **/

static int ip6_tnl_xmit2(struct sk_buff *skb,
                   struct net_device *dev,
                   __u8 dsfield,
                   struct flowi *fl,
                   int encap_limit,
                   __u32 *pmtu)
{
      struct ip6_tnl *t = netdev_priv(dev);
      struct net_device_stats *stats = &t->stat;
      struct ipv6hdr *ipv6h = ipv6_hdr(skb);
      struct ipv6_tel_txoption opt;
      struct dst_entry *dst;
      struct net_device *tdev;
      int mtu;
      unsigned int max_headroom = sizeof(struct ipv6hdr);
      u8 proto;
      int err = -1;
      int pkt_len;

      if ((dst = ip6_tnl_dst_check(t)) != NULL)
            dst_hold(dst);
      else {
            dst = ip6_route_output(NULL, fl);

            if (dst->error || xfrm_lookup(&dst, fl, NULL, 0) < 0)
                  goto tx_err_link_failure;
      }

      tdev = dst->dev;

      if (tdev == dev) {
            stats->collisions++;
            if (net_ratelimit())
                  printk(KERN_WARNING
                         "%s: Local routing loop detected!\n",
                         t->parms.name);
            goto tx_err_dst_release;
      }
      mtu = dst_mtu(dst) - sizeof (*ipv6h);
      if (encap_limit >= 0) {
            max_headroom += 8;
            mtu -= 8;
      }
      if (mtu < IPV6_MIN_MTU)
            mtu = IPV6_MIN_MTU;
      if (skb->dst)
            skb->dst->ops->update_pmtu(skb->dst, mtu);
      if (skb->len > mtu) {
            *pmtu = mtu;
            err = -EMSGSIZE;
            goto tx_err_dst_release;
      }

      /*
       * Okay, now see if we can stuff it in the buffer as-is.
       */
      max_headroom += LL_RESERVED_SPACE(tdev);

      if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
          (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
            struct sk_buff *new_skb;

            if (!(new_skb = skb_realloc_headroom(skb, max_headroom)))
                  goto tx_err_dst_release;

            if (skb->sk)
                  skb_set_owner_w(new_skb, skb->sk);
            kfree_skb(skb);
            skb = new_skb;
      }
      dst_release(skb->dst);
      skb->dst = dst_clone(dst);

      skb->transport_header = skb->network_header;

      proto = fl->proto;
      if (encap_limit >= 0) {
            init_tel_txopt(&opt, encap_limit);
            ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL);
      }
      skb_push(skb, sizeof(struct ipv6hdr));
      skb_reset_network_header(skb);
      ipv6h = ipv6_hdr(skb);
      *(__be32*)ipv6h = fl->fl6_flowlabel | htonl(0x60000000);
      dsfield = INET_ECN_encapsulate(0, dsfield);
      ipv6_change_dsfield(ipv6h, ~INET_ECN_MASK, dsfield);
      ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
      ipv6h->hop_limit = t->parms.hop_limit;
      ipv6h->nexthdr = proto;
      ipv6_addr_copy(&ipv6h->saddr, &fl->fl6_src);
      ipv6_addr_copy(&ipv6h->daddr, &fl->fl6_dst);
      nf_reset(skb);
      pkt_len = skb->len;
      err = NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, skb, NULL,
                  skb->dst->dev, dst_output);

      if (net_xmit_eval(err) == 0) {
            stats->tx_bytes += pkt_len;
            stats->tx_packets++;
      } else {
            stats->tx_errors++;
            stats->tx_aborted_errors++;
      }
      ip6_tnl_dst_store(t, dst);
      return 0;
tx_err_link_failure:
      stats->tx_carrier_errors++;
      dst_link_failure(skb);
tx_err_dst_release:
      dst_release(dst);
      return err;
}

static inline int
ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      struct iphdr  *iph = ip_hdr(skb);
      int encap_limit = -1;
      struct flowi fl;
      __u8 dsfield;
      __u32 mtu;
      int err;

      if ((t->parms.proto != IPPROTO_IPIP && t->parms.proto != 0) ||
          !ip6_tnl_xmit_ctl(t))
            return -1;

      if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
            encap_limit = t->parms.encap_limit;

      memcpy(&fl, &t->fl, sizeof (fl));
      fl.proto = IPPROTO_IPIP;

      dsfield = ipv4_get_dsfield(iph);

      if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
            fl.fl6_flowlabel |= htonl((__u32)iph->tos << IPV6_TCLASS_SHIFT)
                                & IPV6_TCLASS_MASK;

      err = ip6_tnl_xmit2(skb, dev, dsfield, &fl, encap_limit, &mtu);
      if (err != 0) {
            /* XXX: send ICMP error even if DF is not set. */
            if (err == -EMSGSIZE)
                  icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                          htonl(mtu));
            return -1;
      }

      return 0;
}

static inline int
ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      struct ipv6hdr *ipv6h = ipv6_hdr(skb);
      int encap_limit = -1;
      __u16 offset;
      struct flowi fl;
      __u8 dsfield;
      __u32 mtu;
      int err;

      if ((t->parms.proto != IPPROTO_IPV6 && t->parms.proto != 0) ||
          !ip6_tnl_xmit_ctl(t) || ip6_tnl_addr_conflict(t, ipv6h))
            return -1;

      offset = parse_tlv_tnl_enc_lim(skb, skb_network_header(skb));
      if (offset > 0) {
            struct ipv6_tlv_tnl_enc_lim *tel;
            tel = (struct ipv6_tlv_tnl_enc_lim *)&skb_network_header(skb)[offset];
            if (tel->encap_limit == 0) {
                  icmpv6_send(skb, ICMPV6_PARAMPROB,
                            ICMPV6_HDR_FIELD, offset + 2, skb->dev);
                  return -1;
            }
            encap_limit = tel->encap_limit - 1;
      } else if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
            encap_limit = t->parms.encap_limit;

      memcpy(&fl, &t->fl, sizeof (fl));
      fl.proto = IPPROTO_IPV6;

      dsfield = ipv6_get_dsfield(ipv6h);
      if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
            fl.fl6_flowlabel |= (*(__be32 *) ipv6h & IPV6_TCLASS_MASK);
      if ((t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL))
            fl.fl6_flowlabel |= (*(__be32 *) ipv6h & IPV6_FLOWLABEL_MASK);

      err = ip6_tnl_xmit2(skb, dev, dsfield, &fl, encap_limit, &mtu);
      if (err != 0) {
            if (err == -EMSGSIZE)
                  icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
            return -1;
      }

      return 0;
}

static int
ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      struct net_device_stats *stats = &t->stat;
      int ret;

      if (t->recursion++) {
            t->stat.collisions++;
            goto tx_err;
      }

      switch (skb->protocol) {
      case __constant_htons(ETH_P_IP):
            ret = ip4ip6_tnl_xmit(skb, dev);
            break;
      case __constant_htons(ETH_P_IPV6):
            ret = ip6ip6_tnl_xmit(skb, dev);
            break;
      default:
            goto tx_err;
      }

      if (ret < 0)
            goto tx_err;

      t->recursion--;
      return 0;

tx_err:
      stats->tx_errors++;
      stats->tx_dropped++;
      kfree_skb(skb);
      t->recursion--;
      return 0;
}

static void ip6_tnl_set_cap(struct ip6_tnl *t)
{
      struct ip6_tnl_parm *p = &t->parms;
      int ltype = ipv6_addr_type(&p->laddr);
      int rtype = ipv6_addr_type(&p->raddr);

      p->flags &= ~(IP6_TNL_F_CAP_XMIT|IP6_TNL_F_CAP_RCV);

      if (ltype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
          rtype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
          !((ltype|rtype) & IPV6_ADDR_LOOPBACK) &&
          (!((ltype|rtype) & IPV6_ADDR_LINKLOCAL) || p->link)) {
            if (ltype&IPV6_ADDR_UNICAST)
                  p->flags |= IP6_TNL_F_CAP_XMIT;
            if (rtype&IPV6_ADDR_UNICAST)
                  p->flags |= IP6_TNL_F_CAP_RCV;
      }
}

static void ip6_tnl_link_config(struct ip6_tnl *t)
{
      struct net_device *dev = t->dev;
      struct ip6_tnl_parm *p = &t->parms;
      struct flowi *fl = &t->fl;

      memcpy(&dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
      memcpy(&dev->broadcast, &p->raddr, sizeof(struct in6_addr));

      /* Set up flowi template */
      ipv6_addr_copy(&fl->fl6_src, &p->laddr);
      ipv6_addr_copy(&fl->fl6_dst, &p->raddr);
      fl->oif = p->link;
      fl->fl6_flowlabel = 0;

      if (!(p->flags&IP6_TNL_F_USE_ORIG_TCLASS))
            fl->fl6_flowlabel |= IPV6_TCLASS_MASK & p->flowinfo;
      if (!(p->flags&IP6_TNL_F_USE_ORIG_FLOWLABEL))
            fl->fl6_flowlabel |= IPV6_FLOWLABEL_MASK & p->flowinfo;

      ip6_tnl_set_cap(t);

      if (p->flags&IP6_TNL_F_CAP_XMIT && p->flags&IP6_TNL_F_CAP_RCV)
            dev->flags |= IFF_POINTOPOINT;
      else
            dev->flags &= ~IFF_POINTOPOINT;

      dev->iflink = p->link;

      if (p->flags & IP6_TNL_F_CAP_XMIT) {
            int strict = (ipv6_addr_type(&p->raddr) &
                        (IPV6_ADDR_MULTICAST|IPV6_ADDR_LINKLOCAL));

            struct rt6_info *rt = rt6_lookup(&p->raddr, &p->laddr,
                                     p->link, strict);

            if (rt == NULL)
                  return;

            if (rt->rt6i_dev) {
                  dev->hard_header_len = rt->rt6i_dev->hard_header_len +
                        sizeof (struct ipv6hdr);

                  dev->mtu = rt->rt6i_dev->mtu - sizeof (struct ipv6hdr);

                  if (dev->mtu < IPV6_MIN_MTU)
                        dev->mtu = IPV6_MIN_MTU;
            }
            dst_release(&rt->u.dst);
      }
}

/**
 * ip6_tnl_change - update the tunnel parameters
 *   @t: tunnel to be changed
 *   @p: tunnel configuration parameters
 *   @active: != 0 if tunnel is ready for use
 *
 * Description:
 *   ip6_tnl_change() updates the tunnel parameters
 **/

static int
ip6_tnl_change(struct ip6_tnl *t, struct ip6_tnl_parm *p)
{
      ipv6_addr_copy(&t->parms.laddr, &p->laddr);
      ipv6_addr_copy(&t->parms.raddr, &p->raddr);
      t->parms.flags = p->flags;
      t->parms.hop_limit = p->hop_limit;
      t->parms.encap_limit = p->encap_limit;
      t->parms.flowinfo = p->flowinfo;
      t->parms.link = p->link;
      t->parms.proto = p->proto;
      ip6_tnl_dst_reset(t);
      ip6_tnl_link_config(t);
      return 0;
}

/**
 * ip6_tnl_ioctl - configure ipv6 tunnels from userspace
 *   @dev: virtual device associated with tunnel
 *   @ifr: parameters passed from userspace
 *   @cmd: command to be performed
 *
 * Description:
 *   ip6_tnl_ioctl() is used for managing IPv6 tunnels
 *   from userspace.
 *
 *   The possible commands are the following:
 *     %SIOCGETTUNNEL: get tunnel parameters for device
 *     %SIOCADDTUNNEL: add tunnel matching given tunnel parameters
 *     %SIOCCHGTUNNEL: change tunnel parameters to those given
 *     %SIOCDELTUNNEL: delete tunnel
 *
 *   The fallback device "ip6tnl0", created during module
 *   initialization, can be used for creating other tunnel devices.
 *
 * Return:
 *   0 on success,
 *   %-EFAULT if unable to copy data to or from userspace,
 *   %-EPERM if current process hasn't %CAP_NET_ADMIN set
 *   %-EINVAL if passed tunnel parameters are invalid,
 *   %-EEXIST if changing a tunnel's parameters would cause a conflict
 *   %-ENODEV if attempting to change or delete a nonexisting device
 **/

static int
ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
      int err = 0;
      struct ip6_tnl_parm p;
      struct ip6_tnl *t = NULL;

      switch (cmd) {
      case SIOCGETTUNNEL:
            if (dev == ip6_fb_tnl_dev) {
                  if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p))) {
                        err = -EFAULT;
                        break;
                  }
                  t = ip6_tnl_locate(&p, 0);
            }
            if (t == NULL)
                  t = netdev_priv(dev);
            memcpy(&p, &t->parms, sizeof (p));
            if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof (p))) {
                  err = -EFAULT;
            }
            break;
      case SIOCADDTUNNEL:
      case SIOCCHGTUNNEL:
            err = -EPERM;
            if (!capable(CAP_NET_ADMIN))
                  break;
            err = -EFAULT;
            if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p)))
                  break;
            err = -EINVAL;
            if (p.proto != IPPROTO_IPV6 && p.proto != IPPROTO_IPIP &&
                p.proto != 0)
                  break;
            t = ip6_tnl_locate(&p, cmd == SIOCADDTUNNEL);
            if (dev != ip6_fb_tnl_dev && cmd == SIOCCHGTUNNEL) {
                  if (t != NULL) {
                        if (t->dev != dev) {
                              err = -EEXIST;
                              break;
                        }
                  } else
                        t = netdev_priv(dev);

                  ip6_tnl_unlink(t);
                  err = ip6_tnl_change(t, &p);
                  ip6_tnl_link(t);
                  netdev_state_change(dev);
            }
            if (t) {
                  err = 0;
                  if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof (p)))
                        err = -EFAULT;

            } else
                  err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
            break;
      case SIOCDELTUNNEL:
            err = -EPERM;
            if (!capable(CAP_NET_ADMIN))
                  break;

            if (dev == ip6_fb_tnl_dev) {
                  err = -EFAULT;
                  if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof (p)))
                        break;
                  err = -ENOENT;
                  if ((t = ip6_tnl_locate(&p, 0)) == NULL)
                        break;
                  err = -EPERM;
                  if (t->dev == ip6_fb_tnl_dev)
                        break;
                  dev = t->dev;
            }
            err = 0;
            unregister_netdevice(dev);
            break;
      default:
            err = -EINVAL;
      }
      return err;
}

/**
 * ip6_tnl_get_stats - return the stats for tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Return: stats for device
 **/

static struct net_device_stats *
ip6_tnl_get_stats(struct net_device *dev)
{
      return &(((struct ip6_tnl *)netdev_priv(dev))->stat);
}

/**
 * ip6_tnl_change_mtu - change mtu manually for tunnel device
 *   @dev: virtual device associated with tunnel
 *   @new_mtu: the new mtu
 *
 * Return:
 *   0 on success,
 *   %-EINVAL if mtu too small
 **/

static int
ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
{
      if (new_mtu < IPV6_MIN_MTU) {
            return -EINVAL;
      }
      dev->mtu = new_mtu;
      return 0;
}

/**
 * ip6_tnl_dev_setup - setup virtual tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Description:
 *   Initialize function pointers and device parameters
 **/

static void ip6_tnl_dev_setup(struct net_device *dev)
{
      dev->uninit = ip6_tnl_dev_uninit;
      dev->destructor = free_netdev;
      dev->hard_start_xmit = ip6_tnl_xmit;
      dev->get_stats = ip6_tnl_get_stats;
      dev->do_ioctl = ip6_tnl_ioctl;
      dev->change_mtu = ip6_tnl_change_mtu;

      dev->type = ARPHRD_TUNNEL6;
      dev->hard_header_len = LL_MAX_HEADER + sizeof (struct ipv6hdr);
      dev->mtu = ETH_DATA_LEN - sizeof (struct ipv6hdr);
      dev->flags |= IFF_NOARP;
      dev->addr_len = sizeof(struct in6_addr);
}


/**
 * ip6_tnl_dev_init_gen - general initializer for all tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static inline void
ip6_tnl_dev_init_gen(struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      t->dev = dev;
      strcpy(t->parms.name, dev->name);
}

/**
 * ip6_tnl_dev_init - initializer for all non fallback tunnel devices
 *   @dev: virtual device associated with tunnel
 **/

static int
ip6_tnl_dev_init(struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      ip6_tnl_dev_init_gen(dev);
      ip6_tnl_link_config(t);
      return 0;
}

/**
 * ip6_fb_tnl_dev_init - initializer for fallback tunnel device
 *   @dev: fallback device
 *
 * Return: 0
 **/

static int
ip6_fb_tnl_dev_init(struct net_device *dev)
{
      struct ip6_tnl *t = netdev_priv(dev);
      ip6_tnl_dev_init_gen(dev);
      t->parms.proto = IPPROTO_IPV6;
      dev_hold(dev);
      tnls_wc[0] = t;
      return 0;
}

static struct xfrm6_tunnel ip4ip6_handler = {
      .handler    = ip4ip6_rcv,
      .err_handler      = ip4ip6_err,
      .priority   =     1,
};

static struct xfrm6_tunnel ip6ip6_handler = {
      .handler    = ip6ip6_rcv,
      .err_handler      = ip6ip6_err,
      .priority   =     1,
};

/**
 * ip6_tunnel_init - register protocol and reserve needed resources
 *
 * Return: 0 on success
 **/

static int __init ip6_tunnel_init(void)
{
      int  err;

      if (xfrm6_tunnel_register(&ip4ip6_handler, AF_INET)) {
            printk(KERN_ERR "ip6_tunnel init: can't register ip4ip6\n");
            err = -EAGAIN;
            goto out;
      }

      if (xfrm6_tunnel_register(&ip6ip6_handler, AF_INET6)) {
            printk(KERN_ERR "ip6_tunnel init: can't register ip6ip6\n");
            err = -EAGAIN;
            goto unreg_ip4ip6;
      }
      ip6_fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
                              ip6_tnl_dev_setup);

      if (!ip6_fb_tnl_dev) {
            err = -ENOMEM;
            goto fail;
      }
      ip6_fb_tnl_dev->init = ip6_fb_tnl_dev_init;

      if ((err = register_netdev(ip6_fb_tnl_dev))) {
            free_netdev(ip6_fb_tnl_dev);
            goto fail;
      }
      return 0;
fail:
      xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6);
unreg_ip4ip6:
      xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET);
out:
      return err;
}

static void __exit ip6_tnl_destroy_tunnels(void)
{
      int h;
      struct ip6_tnl *t;

      for (h = 0; h < HASH_SIZE; h++) {
            while ((t = tnls_r_l[h]) != NULL)
                  unregister_netdevice(t->dev);
      }

      t = tnls_wc[0];
      unregister_netdevice(t->dev);
}

/**
 * ip6_tunnel_cleanup - free resources and unregister protocol
 **/

static void __exit ip6_tunnel_cleanup(void)
{
      if (xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET))
            printk(KERN_INFO "ip6_tunnel close: can't deregister ip4ip6\n");

      if (xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6))
            printk(KERN_INFO "ip6_tunnel close: can't deregister ip6ip6\n");

      rtnl_lock();
      ip6_tnl_destroy_tunnels();
      rtnl_unlock();
}

module_init(ip6_tunnel_init);
module_exit(ip6_tunnel_cleanup);

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