On Thu, 15 Jun 2017 10:30:29 +0800
Haishuang Yan <yanhaishu...@cmss.chinamobile.com> wrote:
> Same as ip_gre, geneve and vxlan, use key->tos as tos value.
>
> CC: Peter Dawson <peted...@gmail.com>
> Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on
> encapsulated packets”)
> Suggested-by: Daniel Borkmann <dan...@iogearbox.net>
> Signed-off-by: Haishuang Yan <yanhaishu...@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.
