net: gre: provide multicast mappings for ipv4 and ipv6

My commit 6d55cb91a0020ac0 (gre: fix hard header destination
address checking) broke multicast.

The reason is that ip_gre used to get ipgre_header() calls with
zero destination if we have NOARP or multicast destination. Instead
the actual target was decided at ipgre_tunnel_xmit() time based on
per-protocol dissection.

Instead of allowing the "abuse" of ->header() calls with invalid
destination, this creates multicast mappings for ip_gre. This also
fixes "ip neigh show nud noarp" to display the proper multicast
mappings used by the gre device.

Reported-by: Doug Kehn <rdkehn@yahoo.com>
Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Acked-by: Doug Kehn <rdkehn@yahoo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 5 insertions, 0 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 090d273d7865..1b74d3b64371 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -215,6 +215,9 @@ int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
         case ARPHRD_INFINIBAND:
                 ip_ib_mc_map(addr, dev->broadcast, haddr);
                 return 0;
+        case ARPHRD_IPGRE:
+                ip_ipgre_mc_map(addr, dev->broadcast, haddr);
+                return 0;
         default:
                 if (dir) {
                         memcpy(haddr, dev->broadcast, dev->addr_len);
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 0e49c9db3c98..92f952d093db 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -341,6 +341,8 @@ int ndisc_mc_map(struct in6_addr *addr, char *buf, struct net_device *dev, int d
         case ARPHRD_INFINIBAND:
                 ipv6_ib_mc_map(addr, dev->broadcast, buf);
                 return 0;
+        case ARPHRD_IPGRE:
+                return ipv6_ipgre_mc_map(addr, dev->broadcast, buf);
         default:
                 if (dir) {
                         memcpy(buf, dev->broadcast, dev->addr_len);