net: Fix GRE RX to use skb_transport_header for GRE header offset
GRE assumes that the GRE header is at skb_network_header +
ip_hrdlen(skb). It is more general to use skb_transport_header
and this allows the possbility of inserting additional header
between IP and GRE (which is what we will done in Generic UDP
Encapsulation for GRE).
Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 7e0756d..4a7b5b2 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -98,7 +98,6 @@
static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
bool *csum_err)
{
- unsigned int ip_hlen = ip_hdrlen(skb);
const struct gre_base_hdr *greh;
__be32 *options;
int hdr_len;
@@ -106,7 +105,7 @@
if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
return -EINVAL;
- greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
+ greh = (struct gre_base_hdr *)skb_transport_header(skb);
if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
return -EINVAL;
@@ -116,7 +115,7 @@
if (!pskb_may_pull(skb, hdr_len))
return -EINVAL;
- greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
+ greh = (struct gre_base_hdr *)skb_transport_header(skb);
tpi->proto = greh->protocol;
options = (__be32 *)(greh + 1);