[IPV4] ip_gre: sendto/recvfrom NBMA address

When GRE tunnel is in NBMA mode, this patch allows an application to use
a PF_PACKET socket to:
- send a packet to specific NBMA address with sendto()
- use recvfrom() to receive packet and check which NBMA address it came from

This is required to implement properly NHRP over GRE tunnel.

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 1 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index f151900efaf9..c5b77bbbe844 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1033,7 +1033,6 @@ static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
         return 0;
 }
 
-#ifdef CONFIG_NET_IPGRE_BROADCAST
 /* Nice toy. Unfortunately, useless in real life :-)
    It allows to construct virtual multiprotocol broadcast "LAN"
    over the Internet, provided multicast routing is tuned.
@@ -1092,10 +1091,19 @@ static int ipgre_header(struct sk_buff *skb, struct net_device *dev,
         return -t->hlen;
 }
 
+static int ipgre_header_parse(const struct sk_buff *skb, unsigned char *haddr)
+{
+        struct iphdr *iph = (struct iphdr*) skb_mac_header(skb);
+        memcpy(haddr, &iph->saddr, 4);
+        return 4;
+}
+
 static const struct header_ops ipgre_header_ops = {
         .create = ipgre_header,
+        .parse  = ipgre_header_parse,
 };
 
+#ifdef CONFIG_NET_IPGRE_BROADCAST
 static int ipgre_open(struct net_device *dev)
 {
         struct ip_tunnel *t = netdev_priv(dev);
@@ -1197,6 +1205,8 @@ static int ipgre_tunnel_init(struct net_device *dev)
                         dev->stop = ipgre_close;
                 }
 #endif
+        } else {
+                dev->header_ops = &ipgre_header_ops;
         }
 
         if (!tdev && tunnel->parms.link)