[IPV6] MROUTE: Support multicast forwarding.

Based on ancient patch by Mickael Hoerdt
<hoerdt@clarinet.u-strasbg.fr>, which is available at
<http://www-r2.u-strasbg.fr/~hoerdt/dev/linux_ipv6_mforwarding/patch-linux-ipv6-mforwarding-0.1a>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

1 files changed, 68 insertions, 19 deletions

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 43a617e2268b..09a3201e408a 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -29,6 +29,7 @@
 #include <linux/netdevice.h>
 #include <linux/in6.h>
 #include <linux/icmpv6.h>
+#include <linux/mroute6.h>
 
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
@@ -236,36 +237,84 @@ int ip6_mc_input(struct sk_buff *skb)
         hdr = ipv6_hdr(skb);
         deliver = ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
 
+#ifdef CONFIG_IPV6_MROUTE
         /*
-         *      IPv6 multicast router mode isnt currently supported.
+         *      IPv6 multicast router mode is now supported ;)
          */
-#if 0
-        if (ipv6_config.multicast_route) {
-                int addr_type;
-
-                addr_type = ipv6_addr_type(&hdr->daddr);
-
-                if (!(addr_type & (IPV6_ADDR_LOOPBACK | IPV6_ADDR_LINKLOCAL))) {
-                        struct sk_buff *skb2;
-                        struct dst_entry *dst;
+        if (ipv6_devconf.mc_forwarding &&
+            likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
+                /*
+                 * Okay, we try to forward - split and duplicate
+                 * packets.
+                 */
+                struct sk_buff *skb2;
+                struct inet6_skb_parm *opt = IP6CB(skb);
+
+                /* Check for MLD */
+                if (unlikely(opt->ra)) {
+                        /* Check if this is a mld message */
+                        u8 *ptr = skb_network_header(skb) + opt->ra;
+                        struct icmp6hdr *icmp6;
+                        u8 nexthdr = hdr->nexthdr;
+                        int offset;
+
+                        /* Check if the value of Router Alert
+                         * is for MLD (0x0000).
+                         */
+                        if ((ptr[2] | ptr[3]) == 0) {
+                                if (!ipv6_ext_hdr(nexthdr)) {
+                                        /* BUG */
+                                        goto discard;
+                                }
+                                offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
+                                                          &nexthdr);
+                                if (offset < 0)
+                                        goto discard;
+
+                                if (nexthdr != IPPROTO_ICMPV6)
+                                        goto discard;
+
+                                if (!pskb_may_pull(skb, (skb_network_header(skb) +
+                                                   offset + 1 - skb->data)))
+                                        goto discard;
+
+                                icmp6 = (struct icmp6hdr *)(skb_network_header(skb) + offset);
+
+                                switch (icmp6->icmp6_type) {
+                                case ICMPV6_MGM_QUERY:
+                                case ICMPV6_MGM_REPORT:
+                                case ICMPV6_MGM_REDUCTION:
+                                case ICMPV6_MLD2_REPORT:
+                                        break;
+                                default:
+                                        /* Bogus */
+                                        goto discard;
+                                }
+                                deliver = 1;
+                                goto out;
+                        }
+                        /* unknown RA - process it normally */
+                }
 
-                        dst = skb->dst;
+                if (deliver)
+                        skb2 = skb_clone(skb, GFP_ATOMIC);
+                else {
+                        skb2 = skb;
+                        skb = NULL;
+                }
 
-                        if (deliver) {
-                                skb2 = skb_clone(skb, GFP_ATOMIC);
-                                dst_output(skb2);
-                        } else {
-                                dst_output(skb);
-                                return 0;
-                        }
+                if (skb2) {
+                        skb2->dev = skb2->dst->dev;
+                        ip6_mr_input(skb2);
                 }
         }
 #endif
-
+out:
         if (likely(deliver)) {
                 ip6_input(skb);
                 return 0;
         }
+discard:
         /* discard */
         kfree_skb(skb);