xfrm: use gre key as flow upper protocol info

The GRE Key field is intended to be used for identifying an individual
traffic flow within a tunnel. It is useful to be able to have XFRM
policy selector matches to have different policies for different
GRE tunnels.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 22 insertions, 5 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index cab2057d5430..aace653710f6 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -779,9 +779,9 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
                                         .tos = RT_TOS(tos)
                                 }
                         },
-                        .proto = IPPROTO_GRE
-                }
-;
+                        .proto = IPPROTO_GRE,
+                        .fl_gre_key = tunnel->parms.o_key
+                };
                 if (ip_route_output_key(dev_net(dev), &rt, &fl)) {
                         dev->stats.tx_carrier_errors++;
                         goto tx_error;
@@ -958,7 +958,8 @@ static int ipgre_tunnel_bind_dev(struct net_device *dev)
                                         .tos = RT_TOS(iph->tos)
                                 }
                         },
-                        .proto = IPPROTO_GRE
+                        .proto = IPPROTO_GRE,
+                        .fl_gre_key = tunnel->parms.o_key
                 };
                 struct rtable *rt;
 
@@ -1223,7 +1224,8 @@ static int ipgre_open(struct net_device *dev)
                                         .tos = RT_TOS(t->parms.iph.tos)
                                 }
                         },
-                        .proto = IPPROTO_GRE
+                        .proto = IPPROTO_GRE,
+                        .fl_gre_key = t->parms.o_key
                 };
                 struct rtable *rt;
 
diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
index dd1fd8c473fc..4a8c5335770c 100644
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -11,6 +11,7 @@
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/inetdevice.h>
+#include <linux/if_tunnel.h>
 #include <net/dst.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
@@ -154,6 +155,20 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
                                 fl->fl_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
                         }
                         break;
+
+                case IPPROTO_GRE:
+                        if (pskb_may_pull(skb, xprth + 12 - skb->data)) {
+                                __be16 *greflags = (__be16 *)xprth;
+                                __be32 *gre_hdr = (__be32 *)xprth;
+
+                                if (greflags[0] & GRE_KEY) {
+                                        if (greflags[0] & GRE_CSUM)
+                                                gre_hdr++;
+                                        fl->fl_gre_key = gre_hdr[1];
+                                }
+                        }
+                        break;
+
                 default:
                         fl->fl_ipsec_spi = 0;
                         break;