[PATCH] net: Fix GRE RX to use skb_transport_header for GRE header offset

[PATCH] net: Fix GRE RX to use skb_transport_header for GRE header offset

[Tom Herbert]

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>
---
 net/ipv4/gre_demux.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

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 @@ EXPORT_SYMBOL_GPL(gre_build_header);
 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 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 	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 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 	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);
-- 
2.1.0.rc2.206.gedb03e5

Re: [PATCH] net: Fix GRE RX to use skb_transport_header for GRE header offset

[Eric Dumazet]

On Mon, 2014-09-08 at 08:29 -0700, Tom Herbert wrote:
> 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>
> ---
>  net/ipv4/gre_demux.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)

I am always confused why you do not include prior Acked-by when you
repost same patch.

This forces me to add it again.

Note this should be a net-next patch, right ?

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH] net: Fix GRE RX to use skb_transport_header for GRE header offset

[Tom Herbert]

On Mon, Sep 8, 2014 at 8:50 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Mon, 2014-09-08 at 08:29 -0700, Tom Herbert wrote:
>> 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>
>> ---
>>  net/ipv4/gre_demux.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> I am always confused why you do not include prior Acked-by when you
> repost same patch.
>
Sorry, I'll do that next time.

> This forces me to add it again.
>
> Note this should be a net-next patch, right ?
>
Yes.

> Acked-by: Eric Dumazet <edumazet@google.com>
>
>

Re: [PATCH] net: Fix GRE RX to use skb_transport_header for GRE header offset

[David Miller]

From: Tom Herbert <therbert@google.com>
Date: Mon,  8 Sep 2014 08:29:12 -0700

> 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>

Applied, thanks Tom.