[PATCH v2] ip6_tunnel: Correct tos value in collect_md mode

[PATCH v2] ip6_tunnel: Correct tos value in collect_md mode

[Haishuang Yan]

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

Re: [PATCH v2] ip6_tunnel: Correct tos value in collect_md mode

[Peter Dawson]

On Thu, 15 Jun 2017 10:30:29 +0800
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 */

I don't think it is correct to apply RT_TOS

Here is my understanding based on the RFCs.

IPv4/6 Header:0 |0 1 2 3 |0 1 2 3 |0 1 2 3 |0 1 2 3 |
RFC2460(IPv6)   |Version | Traffic Class   |        |
RFC2474(IPv6)   |Version | DSCP        |ECN|        |
RFC2474(IPv4)   |Version |  IHL   |    DSCP     |ECN|
RFC1349(IPv4)   |Version |  IHL   | PREC |  TOS   |X|     
RFC791 (IPv4)   |Version |  IHL   |      TOS        |

u8 key->tos stores the full 8bits of Traffic class from an IPv6 header and;
u8 key->tos stores the full 8bits of TOS(RFC791) from an IPv4 header
u8 ip6_tclass will return the full 8bits of Traffic Class from an IPv6 flowlabel

RT_TOS will return the RFC1349 4bit TOS field.

Applying RT_TOS to a key->tos will result in lost information and the inclusion of 1 bit of ECN if the original field was a DSCP+ECN.

Based on this understanding of the RFCs (but not years of experience) and since RFC1349 has been obsoleted by RFC2474 I think the use of RT_TOS should be deprecated.

This being said, dsfield = ip6_tclass(key->label) = key->tos isn't fully correct either because the result will contain the ECN bits as well as the DSCP.

I agree that code should be consistent, but not where there is a potential issue.

Re: [PATCH v2] ip6_tunnel: Correct tos value in collect_md mode

[Daniel Borkmann]

On 06/15/2017 05:54 AM, Peter Dawson wrote:
> On Thu, 15 Jun 2017 10:30:29 +0800
> 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 */
>
> I don't think it is correct to apply RT_TOS
>
> Here is my understanding based on the RFCs.
>
> IPv4/6 Header:0 |0 1 2 3 |0 1 2 3 |0 1 2 3 |0 1 2 3 |
> RFC2460(IPv6)   |Version | Traffic Class   |        |
> RFC2474(IPv6)   |Version | DSCP        |ECN|        |
> RFC2474(IPv4)   |Version |  IHL   |    DSCP     |ECN|
> RFC1349(IPv4)   |Version |  IHL   | PREC |  TOS   |X|
> RFC791 (IPv4)   |Version |  IHL   |      TOS        |
>
> u8 key->tos stores the full 8bits of Traffic class from an IPv6 header and;
> u8 key->tos stores the full 8bits of TOS(RFC791) from an IPv4 header
> u8 ip6_tclass will return the full 8bits of Traffic Class from an IPv6 flowlabel
>
> RT_TOS will return the RFC1349 4bit TOS field.
>
> Applying RT_TOS to a key->tos will result in lost information and the inclusion of 1 bit of ECN if the original field was a DSCP+ECN.
>
> Based on this understanding of the RFCs (but not years of experience) and since RFC1349 has been obsoleted by RFC2474 I think the use of RT_TOS should be deprecated.
>
> This being said, dsfield = ip6_tclass(key->label) = key->tos isn't fully correct either because the result will contain the ECN bits as well as the DSCP.
>
> I agree that code should be consistent, but not where there is a potential issue.

Yeah, you're right. Looks like initial dsfield = key->tos diff was
the better choice then, sorry for my confusing comment.

For example, bpf_skb_set_tunnel_key() helper that populates the collect
metadata as one user of this infra masks the key->label so that it really
only holds the label meaning previous dsfield = ip6_tclass(key->label)
will always be 0 in that case unlike key->tos that actually gets populated
and would propagate it.

Re: [PATCH v2] ip6_tunnel: Correct tos value in collect_md mode

[严海双]

> On 16 Jun 2017, at 10:44 PM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> 
> On 06/15/2017 05:54 AM, Peter Dawson wrote:
>> On Thu, 15 Jun 2017 10:30:29 +0800
>> 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 */
>> 
>> I don't think it is correct to apply RT_TOS
>> 
>> Here is my understanding based on the RFCs.
>> 
>> IPv4/6 Header:0 |0 1 2 3 |0 1 2 3 |0 1 2 3 |0 1 2 3 |
>> RFC2460(IPv6)   |Version | Traffic Class   |        |
>> RFC2474(IPv6)   |Version | DSCP        |ECN|        |
>> RFC2474(IPv4)   |Version |  IHL   |    DSCP     |ECN|
>> RFC1349(IPv4)   |Version |  IHL   | PREC |  TOS   |X|
>> RFC791 (IPv4)   |Version |  IHL   |      TOS        |
>> 
>> u8 key->tos stores the full 8bits of Traffic class from an IPv6 header and;
>> u8 key->tos stores the full 8bits of TOS(RFC791) from an IPv4 header
>> u8 ip6_tclass will return the full 8bits of Traffic Class from an IPv6 flowlabel
>> 
>> RT_TOS will return the RFC1349 4bit TOS field.
>> 
>> Applying RT_TOS to a key->tos will result in lost information and the inclusion of 1 bit of ECN if the original field was a DSCP+ECN.
>> 
>> Based on this understanding of the RFCs (but not years of experience) and since RFC1349 has been obsoleted by RFC2474 I think the use of RT_TOS should be deprecated.
>> 
>> This being said, dsfield = ip6_tclass(key->label) = key->tos isn't fully correct either because the result will contain the ECN bits as well as the DSCP.
>> 
>> I agree that code should be consistent, but not where there is a potential issue.
> 
> Yeah, you're right. Looks like initial dsfield = key->tos diff was
> the better choice then, sorry for my confusing comment.
> 
> For example, bpf_skb_set_tunnel_key() helper that populates the collect
> metadata as one user of this infra masks the key->label so that it really
> only holds the label meaning previous dsfield = ip6_tclass(key->label)
> will always be 0 in that case unlike key->tos that actually gets populated
> and would propagate it.
> 
Okay, I will change the commit back to initial version, thanks everyone.