[IPV6]: Add RFC4214 support

This patch includes support for the Intra-Site Automatic Tunnel
Addressing Protocol (ISATAP) per RFC4214. It uses the SIT
module, and is configured using extensions to the "iproute2"
utility. The diffs are specific to the Linux 2.6.24-rc2 kernel
distribution.

This version includes the diff for ./include/linux/if.h which was
missing in the v2.4 submission and is needed to make the
patch compile. The patch has been installed, compiled and
tested in a clean 2.6.24-rc2 kernel build area.

Signed-off-by: Fred L. Templin <fred.l.templin@boeing.com>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 77 insertions, 0 deletions

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 71433d29d884..b3b8513e9cb7 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -16,6 +16,7 @@
  *      Changes:
  * Roger Venning <r.venning@telstra.com>:       6to4 support
  * Nate Thompson <nate@thebog.net>:             6to4 support
+ * Fred L. Templin <fltemplin@acm.org>:         isatap support
  */
 
 #include <linux/module.h>
@@ -182,6 +183,9 @@ static struct ip_tunnel * ipip6_tunnel_locate(struct ip_tunnel_parm *parms, int
         dev->init = ipip6_tunnel_init;
         nt->parms = *parms;
 
+        if (parms->i_flags & SIT_ISATAP)
+                dev->priv_flags |= IFF_ISATAP;
+
         if (register_netdevice(dev) < 0) {
                 free_netdev(dev);
                 goto failed;
@@ -364,6 +368,48 @@ static inline void ipip6_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
                 IP6_ECN_set_ce(ipv6_hdr(skb));
 }
 
+/* ISATAP (RFC4214) - check source address */
+static int
+isatap_srcok(struct sk_buff *skb, struct iphdr *iph, struct net_device *dev)
+{
+        struct neighbour *neigh;
+        struct dst_entry *dst;
+        struct rt6_info *rt;
+        struct flowi fl;
+        struct in6_addr *addr6;
+        struct in6_addr rtr;
+        struct ipv6hdr *iph6;
+        int ok = 0;
+
+        /* from onlink default router */
+        ipv6_addr_set(&rtr,  htonl(0xFE800000), 0, 0, 0);
+        ipv6_isatap_eui64(rtr.s6_addr + 8, iph->saddr);
+        if ((rt = rt6_get_dflt_router(&rtr, dev))) {
+                dst_release(&rt->u.dst);
+                return 1;
+        }
+
+        iph6 = ipv6_hdr(skb);
+        memset(&fl, 0, sizeof(fl));
+        fl.proto = iph6->nexthdr;
+        ipv6_addr_copy(&fl.fl6_dst, &iph6->saddr);
+        fl.oif = dev->ifindex;
+        security_skb_classify_flow(skb, &fl);
+
+        dst = ip6_route_output(NULL, &fl);
+        if (!dst->error && (dst->dev == dev) && (neigh = dst->neighbour)) {
+
+                addr6 = (struct in6_addr*)&neigh->primary_key;
+
+                /* from correct previous hop */
+                if (ipv6_addr_is_isatap(addr6) &&
+                    (addr6->s6_addr32[3] == iph->saddr))
+                        ok = 1;
+        }
+        dst_release(dst);
+        return ok;
+}
+
 static int ipip6_rcv(struct sk_buff *skb)
 {
         struct iphdr *iph;
@@ -382,6 +428,14 @@ static int ipip6_rcv(struct sk_buff *skb)
                 IPCB(skb)->flags = 0;
                 skb->protocol = htons(ETH_P_IPV6);
                 skb->pkt_type = PACKET_HOST;
+
+                if ((tunnel->dev->priv_flags & IFF_ISATAP) &&
+                    !isatap_srcok(skb, iph, tunnel->dev)) {
+                        tunnel->stat.rx_errors++;
+                        read_unlock(&ipip6_lock);
+                        kfree_skb(skb);
+                        return 0;
+                }
                 tunnel->stat.rx_packets++;
                 tunnel->stat.rx_bytes += skb->len;
                 skb->dev = tunnel->dev;
@@ -444,6 +498,29 @@ static int ipip6_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
         if (skb->protocol != htons(ETH_P_IPV6))
                 goto tx_error;
 
+        /* ISATAP (RFC4214) - must come before 6to4 */
+        if (dev->priv_flags & IFF_ISATAP) {
+                struct neighbour *neigh = NULL;
+
+                if (skb->dst)
+                        neigh = skb->dst->neighbour;
+
+                if (neigh == NULL) {
+                        if (net_ratelimit())
+                                printk(KERN_DEBUG "sit: nexthop == NULL\n");
+                        goto tx_error;
+                }
+
+                addr6 = (struct in6_addr*)&neigh->primary_key;
+                addr_type = ipv6_addr_type(addr6);
+
+                if ((addr_type & IPV6_ADDR_UNICAST) &&
+                     ipv6_addr_is_isatap(addr6))
+                        dst = addr6->s6_addr32[3];
+                else
+                        goto tx_error;
+        }
+
         if (!dst)
                 dst = try_6to4(&iph6->daddr);