[PATCH net] net: ip6_gre: use erspan key field for tunnel lookup

[Lorenzo Bianconi]

Use ERSPAN key header field as tunnel key in gre_parse_header routine
since ERSPAN protocol sets the key field of the external GRE header to
0 resulting in a possible tunnel lookup fail.
In addition remove key field parsing in erspan_rcv and ip6erspan_rcv

Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianc...@redhat.com>
---
 net/ipv4/gre_demux.c | 14 ++++++++++++++
 net/ipv4/ip_gre.c    |  4 ----
 net/ipv6/ip6_gre.c   |  1 -
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index a4bf22ee3aed..ee09d657606e 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -25,6 +25,7 @@
 #include <linux/spinlock.h>
 #include <net/protocol.h>
 #include <net/gre.h>
+#include <net/erspan.h>
 
 #include <net/icmp.h>
 #include <net/route.h>
@@ -119,6 +120,19 @@ int gre_parse_header(struct sk_buff *skb, struct 
tnl_ptk_info *tpi,
                        hdr_len += 4;
        }
        tpi->hdr_len = hdr_len;
+
+       /* ERSPAN ver 1 and 2 protocol sets GRE key field
+        * to 0 and sets the configured key in the
+        * inner erspan header field
+        */
+       if (tpi->proto == htons(ETH_P_ERSPAN) ||
+           tpi->proto == htons(ETH_P_ERSPAN2)) {
+               struct erspan_base_hdr *ershdr;
+
+               ershdr = (struct erspan_base_hdr *)options;
+               tpi->key = cpu_to_be32(get_session_id(ershdr));
+       }
+
        return hdr_len;
 }
 EXPORT_SYMBOL(gre_parse_header);
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index d1d09f3e5f9e..c9238ca67413 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -278,10 +278,6 @@ static int erspan_rcv(struct sk_buff *skb, struct 
tnl_ptk_info *tpi,
        ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);
        ver = ershdr->ver;
 
-       /* The original GRE header does not have key field,
-        * Use ERSPAN 10-bit session ID as key.
-        */
-       tpi->key = cpu_to_be32(get_session_id(ershdr));
        tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
                                  tpi->flags | TUNNEL_KEY,
                                  iph->saddr, iph->daddr, tpi->key);
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 09d0826742f8..961a96355ddb 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -540,7 +540,6 @@ static int ip6erspan_rcv(struct sk_buff *skb, int 
gre_hdr_len,
        ipv6h = ipv6_hdr(skb);
        ershdr = (struct erspan_base_hdr *)skb->data;
        ver = ershdr->ver;
-       tpi->key = cpu_to_be32(get_session_id(ershdr));
 
        tunnel = ip6gre_tunnel_lookup(skb->dev,
                                      &ipv6h->saddr, &ipv6h->daddr, tpi->key,
-- 
2.20.1