ip6_tunnel: Correct tos value in collect_md mode

Same as ip_gre, geneve and vxlan, use key->tos as tos value.

CC: Peter Dawson <petedaws@gmail.com>
Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on
encapsulated packets”)
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

---
Changes since v2:
  * Add fixes information
  * mask key->tos with RT_TOS() suggested by Daniel
---
 net/ipv6/ip6_tunnel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

> On 14 Jun 2017, at 10:48 AM, Haishuang Yan <yanhaishuang@cmss.chinamobile.com> wrote:
> 
> Same as ip_gre, geneve and vxlan, use key->tos as tos value.
> 
> CC: Peter Dawson <petedaws@gmail.com>
> Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on
> encapsulated packets”)
> Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
> 
> ---
> Changes since v2:
>  * Add fixes information
>  * mask key->tos with RT_TOS() suggested by Daniel
> ---
> net/ipv6/ip6_tunnel.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
> index ef99d59..6400726 100644
> --- a/net/ipv6/ip6_tunnel.c
> +++ b/net/ipv6/ip6_tunnel.c
> @@ -1249,7 +1249,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
> 		fl6.flowi6_proto = IPPROTO_IPIP;
> 		fl6.daddr = key->u.ipv6.dst;
> 		fl6.flowlabel = key->label;
> -		dsfield = ip6_tclass(key->label);
> +		dsfield =  RT_TOS(key->tos);
> 	} else {
> 		if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
> 			encap_limit = t->parms.encap_limit;
> @@ -1320,7 +1320,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
> 		fl6.flowi6_proto = IPPROTO_IPV6;
> 		fl6.daddr = key->u.ipv6.dst;
> 		fl6.flowlabel = key->label;
> -		dsfield = ip6_tclass(key->label);
> +		dsfield = RT_TOS(key->tos);
> 	} else {
> 		offset = ip6_tnl_parse_tlv_enc_lim(skb, skb_network_header(skb));
> 		/* ip6_tnl_parse_tlv_enc_lim() might have reallocated skb->head */
> -- 
> 1.8.3.1
> 
> 

Sorry, I forgot to add subject prefix, please ignore this patch.

On Wed, 14 Jun 2017 10:54:31 +0800
严海双 <yanhaishuang@cmss.chinamobile.com> wrote:


> > Changes since v2:
> >  * mask key->tos with RT_TOS() suggested by Daniel

Can you help me understand the rationale for this change? Is there are bug introduced by dsfield = ip6_tclass(key->label); ?

The RT_TOS masks out 4bits of the 8bit tos field in accordance with RFC1349 (obsoleted by RFC2474). IPv6 does not have a TOS field. So it dosen't make sense to apply a TOS value to the outer header of an IPv6 tunnel.

> On 14 Jun 2017, at 1:28 PM, Peter Dawson <petedaws@gmail.com> wrote:
> 
> On Wed, 14 Jun 2017 10:54:31 +0800
> 严海双 <yanhaishuang@cmss.chinamobile.com> wrote:
> 
> 
>>> Changes since v2:
>>> * mask key->tos with RT_TOS() suggested by Daniel
> 
> Can you help me understand the rationale for this change? Is there are bug introduced by dsfield = ip6_tclass(key->label); ?
> 
> The RT_TOS masks out 4bits of the 8bit tos field in accordance with RFC1349 (obsoleted by RFC2474). IPv6 does not have a TOS field. So it dosen't make sense to apply a TOS value to the outer header of an IPv6 tunnel.
> 
> 

Hi, Peter

Here the tos also means Traffic Class in IPv6, see the define in struct ip_tunnel_key:

u8          tos;        /* TOS for IPv4, TC for IPv6 */

RT_TOS mask is suggested by Daniel, please refer to the implement in vxlan or geneve code:

fl6.flowlabel = ip6_make_flowinfo(RT_TOS(tos), label);

Thanks.