[IPV6] IP6TUNNEL: Add support to IPv4 over IPv6 tunnel.

Some notes
- Protocol number IPPROTO_IPIP is used for IPv4 over IPv6 packets.
- If IP6_TNL_F_USE_ORIG_TCLASS is set, TOS in IPv4 header is copied to
  Traffic Class in outer IPv6 header on xmit.
- IP6_TNL_F_USE_ORIG_FLOWLABEL is ignored on xmit of IPv4 packets, because
  IPv4 header does not have flow label.
- Kernel sends ICMP error if IPv4 packet is too big on xmit, even if
  DF flag is not set.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 4546bb923a2060f8ee4681241811ec4d7bf3b05d..a6541495deab57e7c46dc39dfac1e0dc57047240 100644 (file)
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1,14 +1,15 @@
 /*
- *     IPv6 over IPv6 tunnel device
+ *     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
+ *      linux/net/ipv6/sit.c and linux/net/ipv4/ipip.c
  *
  *      RFC 2473
  *
@@ -24,6 +25,7 @@
 #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>
@@ -41,6 +43,7 @@
 #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>
@@ -51,7 +54,7 @@
 #include <net/inet_ecn.h>
 
 MODULE_AUTHOR("Ville Nuorvala");
-MODULE_DESCRIPTION("IPv6-in-IPv6 tunnel");
+MODULE_DESCRIPTION("IPv6 tunneling device");
 MODULE_LICENSE("GPL");
 
 #define IPV6_TLV_TEL_DST_SIZE 8
@@ -63,6 +66,7 @@ MODULE_LICENSE("GPL");
 #endif
 
 #define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
+#define IPV6_TCLASS_SHIFT 20
 
 #define HASH_SIZE  32
 
@@ -469,6 +473,104 @@ out:
        return err;
 }
 
+static int
+ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+          int type, int code, int offset, __u32 info)
+{
+       int rel_msg = 0;
+       int rel_type = type;
+       int rel_code = code;
+       __u32 rel_info = info;
+       int err;
+       struct sk_buff *skb2;
+       struct iphdr *eiph;
+       struct flowi fl;
+       struct rtable *rt;
+
+       err = ip6_tnl_err(skb, 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);
+       skb2->nh.raw = skb2->data;
+       eiph = skb2->nh.iph;
+
+       /* 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);
+               rel_info = htonl(rel_info);
+       }
+
+       icmp_send(skb2, rel_type, rel_code, 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, __u32 info)
@@ -513,6 +615,19 @@ ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
        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(skb->nh.iph, INET_ECN_MASK, dsfield);
+
+       if (INET_ECN_is_ce(dsfield))
+               IP_ECN_set_ce(skb->nh.iph);
+}
+
 static void ip6ip6_dscp_ecn_decapsulate(struct ip6_tnl *t,
                                        struct ipv6hdr *ipv6h,
                                        struct sk_buff *skb)
@@ -605,6 +720,11 @@ discard:
        return 0;
 }
 
+static int ip4ip6_rcv(struct sk_buff *skb)
+{
+       return ip6_tnl_rcv(skb, ETH_P_IP, ip4ip6_dscp_ecn_decapsulate);
+}
+
 static int ip6ip6_rcv(struct sk_buff *skb)
 {
        return ip6_tnl_rcv(skb, ETH_P_IPV6, ip6ip6_dscp_ecn_decapsulate);
@@ -691,7 +811,7 @@ static inline int ip6_tnl_xmit_ctl(struct ip6_tnl *t)
  *   it.
  *
  * Return:
- *   0
+ *   0 on success
  *   -1 fail
  *   %-EMSGSIZE message too big. return mtu in this case.
  **/
@@ -808,6 +928,44 @@ tx_err_dst_release:
        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 = skb->nh.iph;
+       int encap_limit = -1;
+       struct flowi fl;
+       __u8 dsfield;
+       __u32 mtu;
+       int err;
+
+       if (!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 |= ntohl(((__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)
 {
@@ -867,6 +1025,9 @@ ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
        }
 
        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;
@@ -1199,6 +1360,12 @@ ip6ip6_fb_tnl_dev_init(struct net_device *dev)
        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,
@@ -1215,9 +1382,16 @@ static int __init ip6_tunnel_init(void)
 {
        int  err;
 
+       if (xfrm6_tunnel_register(&ip4ip6_handler, AF_INET)) {
+               printk(KERN_ERR "ip4ip6 init: can't register tunnel\n");
+               err = -EAGAIN;
+               goto out;
+       }
+
        if (xfrm6_tunnel_register(&ip6ip6_handler, AF_INET6)) {
                printk(KERN_ERR "ip6ip6 init: can't register tunnel\n");
-               return -EAGAIN;
+               err = -EAGAIN;
+               goto unreg_ip4ip6;
        }
        ip6ip6_fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
                                         ip6ip6_tnl_dev_setup);
@@ -1235,6 +1409,9 @@ static int __init ip6_tunnel_init(void)
        return 0;
 fail:
        xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6);
+unreg_ip4ip6:
+       xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET);
+out:
        return err;
 }
 
@@ -1258,6 +1435,9 @@ static void __exit ip6ip6_destroy_tunnels(void)
 
 static void __exit ip6_tunnel_cleanup(void)
 {
+       if (xfrm6_tunnel_deregister(&ip4ip6_handler, AF_INET))
+               printk(KERN_INFO "ip4ip6 close: can't deregister tunnel\n");
+
        if (xfrm6_tunnel_deregister(&ip6ip6_handler, AF_INET6))
                printk(KERN_INFO "ip6ip6 close: can't deregister tunnel\n");